Every few months a bright star appears in the sky. Sometimes it’s off to the East, bright in the morning before the Sun rises. Other times, you can see it in the West right after the Sun sets.
Experienced stargazers know this isn’t a star at all, of course, it’s Venus. That horrible twin planet, surrounded by a toxic choking atmosphere of superheated carbon dioxide. For a while it becomes the fourth brightest object in the sky: after the Sun, Moon and the International Space Station, if you can believe it.
In dark skies, Venus gets so bright you can even read a book to it.
Inexperienced stargazers, however, suddenly notice this super bright star in the sky. How come they never noticed it before? Was it always right next to the Moon like that? And that’s when the UFO calls to 911 start up.
Credit: nosha (CC BY-SA 2.0)
I know none of them are going to be watching this video. But for everyone else, even mildly interested in the science here, let’s dig into the orbit of Venus, how we finally figured out what that thing is, how you can observe the planet, and some cool tricks Venus can do.
We’ve written several articles on what planet Venus actually is, and why it sucks so much. You know, a runaway greenhouse effect giving the planet 90 times the Earth’s atmospheric pressure at the surface. It’s a 462-degree furnace, anywhere you go, with a rain of sulfuric acid.
A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL
Nope, we’re not going to talk about visiting that place. Instead, we’re just going to talk about looking at it from afar, and how it changed our whole understanding about our place in the Solar System.
Venus is, of course, the second planet from the Sun. But for the vast majority of human history, nobody really understood what it was. It’s easy to see in the sky, even if you live in one of the most light polluted cities on Earth.
Ancient civilizations tried to grapple with what they were looking at, and of course, they assumed there was something supernatural going on. Probably dark and vengeful gods wandering through the heavens, staring down at us with their beady eyes. Judging, always judging. Some civilizations figured out that it’s a single object, while others believed they were looking at two separate entities.
The Ancient Greeks, for example, called the morning edition of Venus Phosphoros, the “Bringer of Light”, and they called the evening star Hesperos, the, uh, “Star of the Evening”. Then they realized it was a single object, and upgraded it to Aphrodite, the goddess of love. The Romans turned that into Venus, and the name stuck.
Andreas Cellarius’s illustration of the Copernican system, from the Harmonia Macrocosmica (1708). Credit: Public Domain
The ancient astronomers assumed the Earth was the center of the Universe, and all the planets and even the Sun and stars revolved around us. but Nicholas Copernicus worked out the true nature of the Solar System in the early 16th century. The Sun was at the center of the Solar System, and all planets, including Earth, orbited around it.
It was a cool story, and nicely fit the motions of the planets, however, the best evidence came almost a century later when Galileo turned his first crude telescope to Venus and realized that the planet goes through phases, just like the Moon. In fact, with a small telescope, you can confirm this all for yourself.
Each of the planets orbit the Sun. Mercury and Venus orbit closer to the Sun, then Earth, then the rest of the planets. When we observe Venus, we look inwards, down towards the Sun. When we see the rest of the planets, we’re looking outward, away from the Sun.
The best analogy is a car race. If you’re in the stands watching those cars go around and around, you’re turning your head back and forth as the cars pointlessly circle in front of you. But to see cars in the ring road around the racetrack, you’ll need to look all the way round you. Make sense?
The orbits of Earth and Venus around the Sun. Credit: Universe Sandbox ²
Here’s a simplified version of the Solar System, with just the Earth, Venus, and the Sun. Earth, as you probably know, takes just over 365 days to go around the Sun, while Venus only takes 225 days to complete an orbit.
Which means that Venus completes more than 3 orbits every time Earth completes 2. Which means that we’re always seeing Venus from different angles compared to the Sun.
Sometimes it’s on the same side of the Sun as us. Other times it’s on the opposite. And sometimes Venus is on one side of the Sun, or the other. For about 9 and a half months, Venus is the evening star, brightening to its maximum, and then it spends another 9 and a half months as the morning star.
When all three are lined up, astronomers call that a conjunction. It’s a superior conjunction if Venus is on the opposite side of the Sun, and an inferior conjunction if it’s between us and the Sun.
When Venus is on either side, we measure its elongation, eastern or western. Because Venus orbits close to the Sun, the absolute maximum it can get is 47-degrees elongation. Make a triangle, where you point one line at the Sun, and another line at Venus, the angle of this triangle can’t get any bigger than 47-degrees.
And this is why we always see Venus relatively close to the Sun in the sky. There are 360 total degrees you can look, but Venus never leaves 90 of them.
The phases of Venus. Credit: Statis Kalyvas – VT-2004 programme
Now, onto the phases. Just like the Moon, when Venus is in between us and the Sun, then all the light is falling on the far side of Venus. The side facing towards the Sun, but facing away from us. Of course, Venus is also hidden by the glare of the Sun, which means we really can’t even see it. The opposite happens when it’s on the other side of the Sun. It would be fully illuminated from our perspective. Too bad we can’t see it in all that glare.
But when Venus is on either side, this is when we can finally see it. As our perspective changes, we’re seeing more and more of the planet illuminated, and less in shadow. We see phases. We can see a crescent Venus, or a quarter Venus, or a gibbous Venus.
When Venus is almost fully illuminated, it’s actually at its dimmest because it’s so far away. Then as it moves higher and higher in the sky, we see less of it illuminated, but more overall surface area, so it gets brighter. The point of maximum brightness, when it’s blazing brighter than almost any other object in the sky is when the greatest amount of surface area of Venus is visible to us. Astronomers call this the greatest illuminated extent.
Venus is beautiful in the evening right now as I’m recording this video. We won’t see it this bright in the evening sky until August 2017, and then March, 2020. So, get out and enjoy it while you can.
When Venus passes directly in front of the Sun, that’s a planetary transit. The last time it happened was back in 2012, and before that, 2004. Unfortunately, the next transit of Venus won’t happen until 2117. I’m sure I’ll be still around, living it up in my robot body.
You’d might wonder why they don’t line up every time Venus passes between the Earth and the Sun. That’s because both Earth and Venus are slightly tilted in their orbits. Sometimes we see Venus above the Sun when it’s directly across from us, other times it’s below the Sun. It’s only after more than 100 years they directly line up again.
A planetary transit of Venus. Credit: NASA/Goddard Space Flight Center/SDO
It turns out that transits of Venus gave us some of the most valuable discoveries in human history.
Today we know that the Sun is approximately 150 million kilometers away. But for the longest time we had no idea how far away the planets are. We know how far away everything is in proportion to everything else, but not in absolute terms.
In 1663, the Scottish mathematician James Gregory calculated that by making very precise measurements of the transits of Venus or Mercury, you could use trigonometry to figure out the actual distance from the Earth to the Sun. The famed astronomer Edumund Halley did even more detailed calculations and suggesedt places on the Earth to make measurements from.
It wasn’t until the 1700s that astronomers got organized enough to make worldwide measurements during a transit of Venus.
Astronomers tried to observe the Venus transit of 1761, but the weather conditions were pretty bad. In the 1769 transit, however, astronomers were sent to various corners of the globe. In Canada, Norway and the South Pacific. Nations fighting each other allowed astronomers safe passage through on ships through the warzone.
All of the observers made 4 observations: when Venus was touching the edge of the Sun, when it was fully inside, when it had touched the other side, and when it was fully out.
By combining all these measurements across the Earth, astronomers calculated that the distance from the Earth to the Sun was 93,726,900 English miles. The most accurate number we have today is 92,955,000 miles, or about 150 million kilometers. They were only off by about 1%. Not bad.
Once we knew the distance from the Earth to the Sun, we could calculate the distance to the other planets, even to other stars. All thanks to Venus.
Venus is one of the most dependable companions we have in the night sky. Sure, it’s a hellish death world, but from our perspective here on Earth, it’s really cool to look at. Don’t miss the next opportunity to see Venus with your own eyeballs. And if you can, get your hands on a telescope and see the planet going through its phases. You won’t regret it.
Did you get a chance to see the last transit of Venus, back in 2012? Give me the details of your experience in the comments.
Venus, Mars, and the waxing crescent moon at dusk from the evening of January 3rd, 2017. Image credit and copyright: Alan Dyer.
Venus, Mars, and the waxing crescent Moon at dusk from the evening of January 3rd, 2017. Image credit and copyright: Alan Dyer.
“What’s that bright light in the sky?” The planet Venus never fails to impress, and indeed makes even seasoned observers look twice at its unexpected brilliance. The third brightest natural object in the sky, Venus now rules the dusk, a fine sight for wintertime evening commuters. Venus reaches greatest elongation tomorrow, a excellent time to admire this dazzling but shrouded world of mystery.
Venus at greatest elongation
Only the two planets interior to Earth’s orbit – Mercury and Venus – can reach a point known as greatest elongation from the Sun. As the name suggests, this is simply the point at which either planet appears to be at its maximum angular distance from the Sun. Think of a big right triangle in space, with Venus or Mercury at the right angle vertex, and the Sun and Earth at the other two corners. High school geometry can come in handy!
Venus at greatest elongation (planets and orbits not to scale). Credit: Dave Dickinson
This Thursday on January 12th Venus reaches a maximum of 47 degrees elongation from the Sun at 11:00 Universal Time (UT) / 6:00 AM Eastern Standard Time, shining at magnitude -4.4. The maximum/minimum elongation for Venus that can occur is 47.3 to 45.4 degrees respectively, and this week’s is the widest until 2025.
Here’s some key dates to watch out for:
Jan 12th: Venus passes less than a degree from Neptune.
Jan 14th: Venus reaches theoretical dichotomy?
Jan 14th: Venus passes 3′ from +3.7 the magnitude star Lambda Aquarii.
Jan 17th: Venus crosses the ecliptic plane northward.
Venus and Mars reach ‘quasi-conjunction’ in late January.
January 30th: Venus crosses the celestial equator northward.
January 31st: The Moon passes 4 degrees south of Venus, and the two also form a nice equilateral triangle with Mars on the same date.
Looking west on the evening of January 31st, 2017. Image credit: Stellarium.
February 17th: Venus reaches a maximum brilliancy of magnitude -4.6.
March 26th: Solar conjunction for Venus occurs eight degrees north of the Sun … it is possible to spy Venus at solar conjunction from high northern latitudes, just be sure to block out the Sun.
Through the telescope, Venus displays a tiny 24.4” size half phase right around greatest elongation. You could stack 74 Venuses across the diameter of tomorrow’s Full Moon. When does Venus look to reach an exact half phase to you? This point, known as theoretical dichotomy, is often off by just a few days. This is a curious observed phenomenon, first noted by German amateur astronomer Johann Schröter in 1793. The effect now bears his name. A result of atmospheric refraction along the day/terminator on Venus, or an optical illusion?
Almost there… a waning gibbous Venus from the evening of January 5th, 2017. Image credit and copyright: Shahrin Ahmad (@Shahgazer)
And hey, amateurs are now using ultraviolet filters to get actual detail on the cloud-tops of Venus… we like to use a variable polarizing filter to cut down the dazzling glare of Venus a bit at the eyepiece.
Also, keep an eye out for another strange phenomenon, known as the Ashen Light of Venus. Now,ashen light or Earthshine is readily apparent on dark side of the Moon, owing to the presence of a large sunlight reflector nearby, namely the Earth. Venus has no such large partner, though astronomers in the early age of telescopic astronomy claimed to have spied a moon of Venus, and even went as far as naming it Neith. An optical illusion? Or real evidence of Venusian sky glow on its nighttime side? After tomorrow, Venus will begin heading between the Earth and the Sun, becoming a slender crescent in the process. Solar conjunction occurs on March 25th, 2017. Venus sits just eight degrees north of the Sun on this date, and viewers in high Arctic latitudes might just be able to spy Venus above the horizon before sunrise on the day of solar conjunction. We performed a similar feat of visual athletics on the morning of January 16th, 1998 observing from North Pole, Alaska.
Venus as seen from Fairbanks, Alaska on the morning of solar conjunction, 2017. Image credit: Starry Night.
From there, Venus heads towards a fine dawn elongation on June 3rd, 2017. All of these events and more are detailed in our free e-book: 101 Astronomical Events for 2017.
Spying Venus in the Daytime
Did you know: you can actually see Venus in the daytime, if you know exactly where to look for it? A deep blue, high contrast sky is the key, and a nearby crescent Moon is handy in your daytime quest. Strange but true fact: Venus is actually brighter than the Moon per square arc second, with a shiny albedo of 70% versus the Moon’s paltry 12%. But Venus is tiny, and hard to spot against the blue daytime sky… until you catch sight of it.
The Moon passing Venus on January 31st, 2017 in the daytime sky. Image credit: Stellarium.
There’s another reason to brave the January cold for northern hemisphere residents: Venus can indeed cast a shadow if you look carefully for it. You’ll need to be away from any other light sources (including the Moon, which passes Full tomorrow as well with the first Full Moon of 2017, known as a Full Wolf Moon). And a high contrast surface such as freshly fallen snow can help… a short time exposure shot can even bring the shadow cast by Venus into focus.
If you follow Venus long enough, you’ll notice a pattern, as it visits very nearly the the same sky environs every eight years and traces out approximately the same path in the dawn and dusk sky. There’s a reason for this: 8 Earth years (8x 365.25 = 2922 days) very nearly equals 5 the synodic periods for Venus (2922/5=584 days, the number of days it takes Venus to return to roughly the same point with respect to the starry background, separate from its true orbit around the Sun of 225 days). For example, Venus last crossed the Pleiades star cluster in 2012, and will do so again in – you guessed it — in 2020. Unfortunately, this pattern isn’t precise, and Venus won’t also transit the Sun again in 2020 like it did in 2012. You’ll have to wait until one century from this year on December 10-11th, 2117 to see that celestial spectacle again….
Hopefully, we’ll have perfected that whole Futurama head-in-a-jar thing by then.
As soon as people learn how inhospitable Mars, Venus, and really the entire Solar System are, they want to know how we can fix it. There’s a word for fixing a planet to make it more like Earth: terraforming.
If you want to fix Mars, all you have to do is thicken and warm up its atmosphere to the point that Earth life could survive. You’d need to do the opposite with Venus, cooling it down and reducing the atmospheric pressure.
But it’s hard to wrap your brain around the scale it would take to do such a thing. We’re talking about an incomprehensible amount of atmosphere to try and modify. The atmospheric pressure on the surface of Venus is 90 times the pressure of Earth. It’s carbon dioxide, so you need some chemical, like magnesium or calcium to lock it away. If you can mine, for example, 4 times the mass of asteroid Vesta, it should be possible.
Credit: NASA/Pat Rawlings
No, from our perspective, that’s practically impossible. In fact, it’s kind of ironic, when you consider the fact that we’re making our own planet less habitable to human civilization every day.
There’s another path to making another world habitable, however, and that’s changing life itself to be more adaptable to surviving on another world.
Instead of terraforming a planet, what if we terraformed ourselves?
Actually, that’s a really bad term. We’d really be changing ourselves to be better adapted to living on Mars. So we’d be Marsiforming ourselves? Venisfying ourselves? Okay, I’ll need to work on the terminology. But you get the gist.
Life, of course, has been evolving and adapting on Earth for at least 4.1 billion years. Pretty much as soon as life could arise on Earth, it did. And those early lifeforms went on to modify and change, adapting to every environment on our planet, from the deepest oceans, to the mountains. From the deserts to the icy tundra.
But in the last few thousand years, we’ve taken a driving role in the evolution of life for the domesticated plants and animals we eat and care for. Your pet dog looks vastly different from the wolf ancestor it evolved from. We’ve increased the yield of corn and wheat, adapted fruit and vegetables, and turned chickens into flightless mobile breast meat.
And in the last few decades, we’ve gained the most powerful new tools for adapting life to our needs: genetic modification. Instead of waiting for evolution and selective breeding to get the results we need, we can rewrite the genetic code of lifeforms, borrowing beneficial traits from life over here, and jamming it into the code of life over there. What doesn’t get cooler when it glows in the dark? Nothing, that’s what.
Can we adapt Earth life to live on Mars? It turns out, our toughest life isn’t that far off. During the American Society for Microbiology meeting in 2015, researchers presented how well tough bacteria would be able to handle the conditions on Mars. They found that 4 species of methanogens might actually be able to survive below the surface, consuming hydrogen and carbon dioxide and releasing methane.
It would still look like a desolate wasteland, but there would be life on Mars even if we have to put it there ourselves. Credit: NASA/JPL
In other words, under the right conditions, there are forms of Earth life that can survive on Mars right now. In fact, as we continue to explore Mars, and learn that it’s wetter than we ever thought, we risk infecting the planet with our own microbial life accidentally.
But when we imagine life on Mars, we’re not thinking about a few hardy methanogens, struggling for life beneath the briny regolith. No, we imagine plants, trees, and little animals scurrying about.
Do we have anything close there that we could adapt?
It turns out there are strains of lichen, the symbiosis of fungi and algae that could stand a chance. You’ve probably seen lichen on rocks and other places that suck for any other lifeform. But according to Jean-Pierre de Vera, with the German Aerospace Center’s Institute of Planetary Research in Berlin, Germany, there are Earth-based lichen which are tough enough.
They put lichen into a test environment that simulated the surface of Mars: low atmospheric pressure, carbon dioxide atmosphere, freezing cold temperatures and high radiation. The only things they couldn’t simulate were galactic radiation and low gravity.
What’s not to lichen about this plan? Credit: Roantrum (CC BY 2.0)
In the harshest conditions, the lichen was barely able to hang on and survive, but in milder Mars conditions, protected within rock cracks, the lichen continued to carry out its regular photosynthesis.
It seems that lichen too is ready to go to Mars.
Methanogens and hardy lichen don’t make for the most thrilling forest canopy. In a second, I’m going to talk about what we can do to tweak life to survive and thrive on Mars. But first, I’d like to thank Zach Kanzler, Jeremy Payne, James Craver, Mike Janzen, and the rest of our 709 patrons for their generous support. If you love what we’re doing and want to help out, head over to patreon.com/universetoday.
If our current life isn’t going to get the job done, well then we’re just going to need to adapt it ourselves. Just like we’ve done in the past, with breeding and more recently with rewriting the DNA itself.
Without dramatically changing the environment of Mars to thicken its atmosphere and boost its temperatures, it’s inconceivable to think that we’ll ever adapt anything more complex than bacteria or lichen to survive outside on Mars. But if those give us a toehold, and other techniques can improve the environment, it’s possible to take incremental steps in that direction.
Engineering concept of a plant growth module. Credit: NASA/Langley
Even within the protected environments of Martian colonies, our current plants and animals probably aren’t up to the task.
The regolith on Mars, for example, contains toxic perchlorates that would kill any Earth-based plants that would try to grow in it. There are Earth-based lifeforms that love perchlorates and it should be possible to create organisms that will strip this toxin out of the regolith and turn it into something useful, like rocket fuel.
Earth-based plants and animals evolved in a 24-hour daily cycle, but a day on Mars is 40 minutes longer than an Earth day. We could grow plants with artificial light, but if we want to use natural Martian light, some adaptation might be required.
Perhaps the biggest risk we face to living on Mars, the one that our technology really can’t help us with is the lower gravity. We don’t know if living in 38% gravity for generations is going to be good for us. We know we can run around on the surface for a few years, but can pregnancy carry to term in this lower gravity?
We just don’t know. In order to find out safely, we’ll need to create rotating space station colonies, where we vary the artificial gravity and see what happens with animals over multiple generations with lower gravity.
A NASA artist’s concept of a vehicle which could provide an artificial-gravity environment of Mars exploration crews. The piloted vehicle rotates around the axis that contains the solar panels. Levels of artificial gravity vary according to the tether length and the rate at which the vehicle spins. Credit: NASA
If there are health problems, we can take the results of these experiments, and modify genetic code to have better adaptation to this environment. And since humans are animals too, the lessons we learn will help us adapt ourselves to be better prepared to survive on Mars, forever.
Here’s a link to an awesome video from Kurzgesagt about the state of genetic engineering, and the amazing technology that’s just around the corner.
If we are able to change humans to live on Mars, we can probably do the same with other worlds. Image a far future, where human colonies on different worlds are adapted to survive there, using a mixture of technology and genetic manipulation. This will be good and bad. On the good side, human colonies will be able to survive over many generations. On the bad side, they might never be able to live anywhere else in the Solar System without going through the whole adaptation process again.
Would you be willing to change your body permanently to be better adapted to live on another world? Let me know your thoughts in the comments.
45P/H-M-P displays a colorful coma and long ion tail on Dec. 22, 2016. Credit: Gerald Rhemann
Comet 45P/Honda-Mrkos-Pajdusakova captured in its glory on Dec. 22, 2016. It displays a bright, well-condensed blue-green coma and long ion or gas tail pointing east. Comet observers take note: a Swan Band filter shows a larger coma and increases the comet’s contrast. Credit: Gerald Rhemann
Merry Christmas and Happy Holidays all! I hope the day finds you in the company of family or friends and feeling at peace. While we’ve been shopping for gifts the past few weeks, a returning comet has been brightening up in the evening sky. Named 45P/Honda-Mrkos-Pajdusakova, it returns to the hood every 5.25 years after vacationing beyond the planet Jupiter. It’s tempting to blow by the name and see only a jumble of letters, but let’s try to pronounce it: HON-da — MUR-Koz — PIE-doo-sha-ko-vah. Not too hard, right?
Tonight, the comet will appear about 12. 5 degrees to the west of Venus in central Capricornus. You can spot it near the end of evening twilight. Use larger binoculars or a telescope. Stellarium
Comet 45P is a short period comet — one with an orbital period of fewer than 200 years — discovered on December 3, 1948 by Minoru Honda along with co-discoverers Antonin Mrkos and Ludmila Pajdusakova. Three names are the maximum a comet can have even if 15 people simultaneously discover it. 45P has a history of brightening rapidly as it approaches the sun, and this go-round is proof. A faint nothing a few weeks back, the comet’s now magnitude +7.5 and visible in 50mm or larger binoculars from low light pollution locations.
You can catch it right around the end of dusk this week and next as it arcs across central Capricornus not far behind the brilliant planet Venus. 45P will look like a dim, fuzzy star in binoculars, but if you can get a telescope on it, you’ll see a fluffy, round coma, a bright, star-like center and perhaps even a faint spike of a tail sticking out to the east. Time exposure photos reveal a tail at least 3° long and a gorgeous, aqua-tinted coma. I saw the color straight off when observing the comet several nights ago in my 15-inch reflector at low power (64x).
Use this map to help you follow the comet night to night. Tick marks start this evening (Dec. 25) and show its nightly position through Jan. 8 around 6 p.m. local time or about an hour and 15 minutes after sunset. Venus, at upper left, is shown through the 28th with stars to magnitude +7. Click the chart for a larger version you can save and print out for use at your telescope. Created with Chris Marriott’s SkyMap software
Right now, and for the remainder of its evening apparition, 45P will never appear very high in the southwestern sky. Look for it a little before the end of evening twilight, when the sky is reasonably dark and the comet is as high as it gets — about a fist above the horizon as seen from mid-northern latitudes. That’s pretty low, so make the best of your time. I recommend you being around 1 hour 15 minutes after sunset.
The further south you live, the higher 45P will appear. To a point. It hovers low at nightfall this month and next. That will change in February when the comet pulls away from the sun and makes a very close approach to the Earth while sailing across the morning sky.
How about a helping hand? On New Year’s Eve, the 2-day-old crescent Moon will be just a few degrees from 45P. This simulation shows the view through 50mm or larger binoculars with an ~6 degree field of view for the Central time zone. Map: Bob King, Source: Stellarium
45P reaches perihelion or closest distance to the sun on Dec. 31 and will remain visible through about Jan. 15 at dusk. An approximately 2-week hiatus follows, when it’s lost in the twilight glow. Then in early February, the comet reappears at dawn and races across Aquila and Hercules, zipping closest to Earth on Feb. 11 at a distance of only 7.7 million miles. During that time, we may even be able to see this little fuzzball with the naked eye; its predicted magnitude of +6 at maximum is right at the naked eye limit. Even in suburban skies, it will make an easy catch in binoculars then.
I’ll update with new charts as we approach that time, plus you can check out this earlier post by fellow Universe Today writer David Dickinson. For now, enjoy the prospect of ‘opening up’ this cometary gift as the last glow of dusk subsides into night.
Welcome back to our planetary weather series! Today, we look at Earth’s overheated “sister planet”, Venus!
Venus is often called Earth’s “Sister Planet” because of all the things they have in common. They are comparable in size, have similar compositions, and both orbit within the Sun’s habitable zone. But beyond that, there are some notable differences that makes Venus a molten hellhole, and about the last place anyone would want to visit!
Much of this has to do with Venus’ atmosphere, which is incredibly dense and entirely hostile to life as we know it. And because of its natural density and composition, the average surface temperature of Venus is hot enough to melt lead. All of this adds up to some pretty interesting weather patterns, which are also incredibly hostile!
Venus Atmosphere:
Although carbon dioxide is invisible, the clouds on Venus are made up of opaque clouds of sulfuric acid, so we can’t see down to the surface using conventional methods. Everything we know about the surface of Venus has been gathered by spacecraft equipped with radar imaging instruments, which can peer through the dense clouds and reveal the surface below.
From the many flybys and atmospheric probes sent into its thick clouds, scientists have learned that Venus’ atmosphere is incredibly dense. In fact, the mass of Venus atmosphere is 93 times that of Earth’s, and the air pressure at the surface is estimated to be as high as 92 bar – i.e. 92 times that of Earth’s at sea level. If it were possible for a human being to stand on the surface of Venus, they would be crushed by the atmosphere.
The composition of the atmosphere is extremely toxic, consisting primarily of carbon dioxide (96.5%) with small amounts of nitrogen (3.5%) and traces of other gases – most notably sulfur dioxide. Combined with its density, the composition generates the strongest greenhouse effect of any planet in the Solar System.
It is also the hottest planet in the Solar System, experiencing mean surface temperatures of 735 K (462 °C; 863.6 °F). Above the dense CO² layer, thick clouds consisting mainly of sulfur dioxide and sulfuric acid droplets scatter about 90% of the sunlight back into space.
The planet is also isothermal, which means that there is little variation in Venus’ surface temperature between day and night, or the equator and the poles. The planet’s minute axial tilt – less than 3° compared to Earth’s 23.5° – and its very slow rotational period (the planet takes around 243 days to complete a single rotation) also minimizes seasonal temperature variation.
Artist’s impression of the surface of Venus. Credit: ESA/AOES
The only appreciable variation in temperature occurs with altitude. The highest point on Venus, Maxwell Montes, is therefore the coolest point on the planet, with a temperature of about 655 K (380 °C; 716 °F) and an atmospheric pressure of about 4.5 MPa (45 bar).
Meteorological Phenomena:
The weather on Venus is one of the aspects of the planet under constant study from Earth-based telescopes and space missions to Venus. And from what we’ve seen, the weather on Venus is very extreme. The entire atmosphere of the planet circulates around quickly, with winds reaching speeds of up to 85 m/s (300 km/h; 186.4 mph) at the cloud tops, which circle the planet every four to five Earth days.
At this speed, these winds move up to 60 times the speed of the planet’s rotation, whereas Earth’s fastest winds are only 10-20% of the planet’s rotational speed. Spacecraft equipped with ultraviolet imaging instruments are able to observe the cloud motion around Venus, and see how it moves at different layers of the atmosphere. The winds blow in a retrograde direction, and are the fastest near the poles.
Closer to the equator, the wind speeds die down to almost nothing. Because of the thick atmosphere, the winds move much slower as you get close to the surface of Venus, reaching speeds of about 5 km/h. Because it’s so thick, though, the atmosphere is more like water currents than blowing wind at the surface, so it is still capable of blowing dust around and moving small rocks across the surface of Venus.
Over the past six years wind speeds in Venus’ atmosphere have been steadily rising (ESA
Several flybys past the planet have also indicated that its dense clouds are capable of producing lightning, much like the clouds on Earth. Their intermittent appearance indicates a pattern associated with weather activity, and the lightning rate is at least half of that on Earth. Since Venus does not experience rainfall (except in the form of sulfuric acid), it has been theorized that the lightning is being caused by a volcanic eruption.
What is the weather like on Venus? Terrible, would be the short answer. The long answer is that it is extremely hot, the air pressure is extremely high, there are very strong winds, sulfuric acid rain (at higher altitudes) and lightning storms driven by volcanic eruptions. It is little wonder then why the only practical option for colonizing Venus involves creating floating cities above the cloud layer.
Science fiction has told us again and again, we belong out there, among the stars. But before we can build that vast galactic empire, we’ve got to learn how to just survive in space. Fortunately, we happen to live in a Solar System with many worlds, large and small that we can use to become a spacefaring civilization.
This is half of an epic two-part article that I’m doing with Isaac Arthur, who runs an amazing YouTube channel all about futurism, often about the exploration and colonization of space. Make sure you subscribe to his channel.
This article is about colonizing the inner Solar System, from tiny Mercury, the smallest planet, out to Mars, the focus of so much attention by Elon Musk and SpaceX. In the other article, Isaac will talk about what it’ll take to colonize the outer Solar System, and harness its icy riches. You can read these articles in either order, just read them both.
At the time I’m writing this, humanity’s colonization efforts of the Solar System are purely on Earth. We’ve exploited every part of the planet, from the South Pole to the North, from huge continents to the smallest islands. There are few places we haven’t fully colonized yet, and we’ll get to that.
But when it comes to space, we’ve only taken the shortest, most tentative steps. There have been a few temporarily inhabited space stations, like Mir, Skylab and the Chinese Tiangong Stations.
Our first and only true colonization of space is the International Space Station, built in collaboration with NASA, ESA, the Russian Space Agency and other countries. It has been permanently inhabited since November 2nd, 2000. Needless to say, we’ve got our work cut out for us.
NASA astronaut Tracy Caldwell Dyson, an Expedition 24 flight engineer in 2010, took a moment during her space station mission to enjoy an unmatched view of home through a window in the Cupola of the International Space Station, the brilliant blue and white part of Earth glowing against the blackness of space. Credits: NASA
Before we talk about the places and ways humans could colonize the rest of the Solar System, it’s important to talk about what it takes to get from place to place.
Just to get from the surface of Earth into orbit around our planet, you need to be going about 10 km/s sideways. This is orbit, and the only way we can do it today is with rockets. Once you’ve gotten into Low Earth Orbit, or LEO, you can use more propellant to get to other worlds.
If you want to travel to Mars, you’ll need an additional 3.6 km/s in velocity to escape Earth gravity and travel to the Red Planet. If you want to go to Mercury, you’ll need another 5.5 km/s.
And if you wanted to escape the Solar System entirely, you’d need another 8.8 km/s. We’re always going to want a bigger rocket.
The most efficient way to transfer from world to world is via the Hohmann Transfer. This is where you raise your orbit and drift out until you cross paths with your destination. Then you need to slow down, somehow, to go into orbit.
One of our primary goals of exploring and colonizing the Solar System will be to gather together the resources that will make future colonization and travel easier. We need water for drinking, and to split it apart for oxygen to breathe. We can also turn this water into rocket fuel. Unfortunately, in the inner Solar System, water is a tough resource to get and will be highly valued.
We need solid ground. To build our bases, to mine our resources, to grow our food, and to protect us from the dangers of space radiation. The more gravity we can get the better, since low gravity softens our bones, weakens our muscles, and harms us in ways we don’t fully understand.
Each world and place we colonize will have advantages and disadvantages. Let’s be honest, Earth is the best place in the Solar System, it’s got everything we could ever want and need. Everywhere else is going to be brutally difficult to colonize and make self-sustaining.
We do have one huge advantage, though. Earth is still here, we can return whenever we like. The discoveries made on our home planet will continue to be useful to humanity in space through communications, and even 3D printing. Once manufacturing is sophisticated enough, a discovery made on one world could be mass produced half a solar system away with the right raw ingredients.
We will learn how to make what we need, wherever we are, and how to transport it from place to place, just like we’ve always done.
Mercury, as imaged by the MESSENGER spacecraft, revealing parts of the never seen by human eyes. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Mercury is the closest planet from the Sun, and one of the most difficult places that we might attempt the colonize. Because it’s so close to the Sun, it receives an enormous amount of energy. During the day, temperatures can reach 427 C, but without an atmosphere to trap the heat, night time temperatures dip down to -173 C. There’s essentially no atmosphere, 38% the gravity of Earth, and a single solar day on Mercury lasts 176 Earth days.
Mercury does have some advantages, though. It has an average density almost as high as Earth, but because of its smaller size, it actually means it has a higher percentage of metal than Earth. Mercury will be incredibly rich in metals and minerals that future colonists will need across the Solar System.
With the lower gravity and no atmosphere, it’ll be far easier to get that material up into orbit and into transfer trajectories to other worlds.
But with the punishing conditions on the planet, how can we live there? Although the surface of Mercury is either scorching or freezing, NASA’s MESSENGER spacecraft turned up regions of the planet which are in eternal shadow near the poles. In fact, these areas seem to have water ice, which is amazing for anywhere this close to the Sun.
Images of Mercury’s northern polar region, provided by MESSENGER. Credit: NASA/JPL
You could imagine future habitats huddled into those craters, pulling in solar power from just over the crater rim, using the reservoirs of water ice for air, fuel and water.
High powered solar robots could scour the surface of Mercury, gathering rare metals and other minerals to be sent off world. Because it’s bathed in the solar winds, Mercury will have large deposits of Helium-3, useful for future fusion reactors.
Over time, more and more of the raw materials of Mercury will find their way to the resource hungry colonies spread across the Solar System.
It also appears there are lava tubes scattered across Mercury, hollows carved out by lava flows millions of years ago. With work, these could be turned into safe, underground habitats, protected from the radiation, high temperatures and hard vacuum on the surface.
With enough engineering ability, future colonists will be able to create habitats on the surface, wherever they like, using a mushroom-shaped heat shield to protect a colony built on stilts to keep it off the sun-baked surface.
Mercury is smaller than Mars, but is a good deal denser, so it has about the same gravity, 38% of Earth’s. Now that might turn out to be just fine, but if we need more, we have the option of using centrifugal force to increase it. Space Stations can generate artificial gravity by spinning, but you can combine normal gravity with spin-gravity to create a stronger field than either would have.
So our mushroom habitat’s stalk could have an interior spinning section with higher gravity for those living inside it. You get a big mirror over it, shielding you from solar radiation and heat, you have stilts holding it off the ground, like roots, that minimize heat transfer from the warmer areas of ground outside the shield, and if you need it you have got a spinning section inside the stalk. A mushroom habitat.
Venus as photographed by the Pioneer spacecraft in 1978. Credit: NASA/JPL/Caltech
Venus is the second planet in the Solar System, and it’s the evil twin of Earth. Even though it has roughly the same size, mass and surface gravity of our planet, it’s way too close to the Sun. The thick atmosphere acts like a blanket, trapping the intense heat, pushing temperatures at the surface to 462 C.
Everywhere on the planet is 462 C, so there’s no place to go that’s cooler. The pure carbon dioxide atmosphere is 90 times thicker than Earth, which is equivalent to being a kilometer beneath the ocean on Earth.
In the beginning, colonizing the surface of Venus defies our ability. How do you survive and stay cool in a thick poisonous atmosphere, hot enough to melt lead? You get above it.
One of the most amazing qualities of Venus is that if you get into the high atmosphere, about 52.5 kilometers up, the air pressure and temperature are similar to Earth. Assuming you can get above the poisonous clouds of sulphuric acid, you could walk outside a floating colony in regular clothes, without a pressure suit. You’d need a source of breathable air, though.
Even better, breathable air is a lifting gas in the cloud tops of Venus. You could imagine a future colony, filled with breathable air, floating around Venus. Because the gravity on Venus is roughly the same as Earth, humans wouldn’t suffer any of the side effects of microgravity. In fact, it might be the only place in the entire Solar System other than Earth where we don’t need to account for low gravity.
Artist’s concept of a Venus cloud city — a possible future outcome of the High Altitude Venus Operational Concept (HAVOC) plan. Credit: Advanced Concepts Lab at NASA Langley Research Center
Now the day on Venus is incredibly long, 243 earth days, so if you stay over the same place the whole time it would be light for four months then dark for four months. Not ideal for solar power on a first glance, but Venus turns so slowly that even at the equator you could stay ahead of the sunset at a fast walk.
So if you have floating colonies it would take very little effort to stay constantly on the light side or dark side or near the twilight zone of the terminator. You are essentially living inside a blimp, so it may as well be mobile. And on the day side it would only take a few solar panels and some propellers to stay ahead. And since it is so close to the Sun, there’s plenty of solar power. What could you do with it?
The atmosphere itself would probably serve as a source of raw materials. Carbon is the basis for all life on Earth. We’ll need it for food and building materials in space. Floating factories could process the thick atmosphere of Venus, to extract carbon, oxygen, and other elements.
Heat resistant robots could be lowered down to the surface to gather minerals and then retrieved before they’re cooked to death.
Venus does have a high gravity, so launching rockets up into space back out of Venus’ gravity well will be expensive.
Over longer periods of time, future colonists might construct large solar shades to shield themselves from the scorching heat, and eventually, even start cooling the planet itself.
Earth as seen on July 6, 2015 from a distance of one million miles by a NASA scientific camera aboard the Deep Space Climate Observatory spacecraft. Credits: NASA
The next planet from the Sun is Earth, the best planet in the Solar System. One of the biggest advantages of our colonization efforts will be to get heavy industry off our planet and into space. Why pollute our atmosphere and rivers when there’s so much more space… in space.
Over time, more and more of the resource gathering will happen off world, with orbital power generation, asteroid mining, and zero gravity manufacturing. Earth’s huge gravity well means that it’s best to bring materials down to Earth, not carry them up to space.
However, the normal gravity, atmosphere and established industry of Earth will allow us to manufacture the lighter high tech goods that the rest of the Solar System will need for their own colonization efforts.
But we haven’t completely colonized Earth itself. Although we’ve spread across the land, we know very little about the deep ocean. Future colonies under the oceans will help us learn more about self-sufficient colonies, in extreme environments. The oceans on Earth will be similar to the oceans on Europa or Enceladus, and the lessons we learn here will teach us to live out there.
As we return to space, we’ll colonize the region around our planet. We’ll construct bigger orbital colonies in Low Earth Orbit, building on our lessons from the International Space Station.
One of the biggest steps we need to take, is understanding how to overcome the debilitating effects of microgravity: the softened bones, weakened muscles and more. We need to perfect techniques for generating artificial gravity where there is none.
A 1969 station concept. The station was to rotate on its central axis to produce artificial gravity. The majority of early space station concepts created artificial gravity one way or another in order to simulate a more natural or familiar environment for the health of the astronauts. Credit: NASA
The best technique we have is rotating spacecraft to generate artificial gravity. Just like we saw in 2001, and The Martian, by rotating all or a portion of a spacecraft, you can generated an outward centrifugal force that mimics the acceleration of gravity. The larger the radius of the space station, the more comfortable and natural the rotation feels.
Low Earth Orbit also keeps a space station within the Earth’s protective magnetosphere, limiting the amount of harmful radiation that future space colonists will experience.
Other orbits are useful too, including geostationary orbit, which is about 36,000 kilometers above the surface of the Earth. Here spacecraft orbit the Earth at exactly the same rate as the rotation of Earth, which means that stations appear in fixed positions above our planet, useful for communication.
Geostationary orbit is higher up in Earth’s gravity well, which means these stations will serve a low-velocity jumping off points to reach other places in the Solar System. They’re also outside the Earth’s atmospheric drag, and don’t require any orbital boosting to keep them in place.
By perfecting orbital colonies around Earth, we’ll develop technologies for surviving in deep space, anywhere in the Solar System. The same general technology will work anywhere, whether we’re in orbit around the Moon, or out past Pluto.
When the technology is advanced enough, we might learn to build space elevators to carry material and up down from Earth’s gravity well. We could also build launch loops, electromagnetic railguns that launch material into space. These launch systems would also be able to loft supplies into transfer trajectories from world to world throughout the Solar System.
Earth orbit, close to the homeworld gives us the perfect place to develop and perfect the technologies we need to become a true spacefaring civilization. Not only that, but we’ve got the Moon.
Sample collection on the surface of the Moon. Apollo 16 astronaut Charles M. Duke Jr. is shown collecting samples with the Lunar Roving Vehicle in the left background. Image: NASA
The Moon, of course, is the Earth’s only natural satellite, which orbits us at an average distance of about 400,000 kilometers. Almost ten times further than geostationary orbit.
The Moon takes a surprising amount of velocity to reach from Low Earth Orbit. It’s close, but expensive to reach, thrust speaking.
But that fact that it’s close makes the Moon an ideal place to colonize. It’s close to Earth, but it’s not Earth. It’s airless, bathed in harmful radiation and has very low gravity. It’s the place that humanity will learn to survive in the harsh environment of space.
But it still does have some resources we can exploit. The lunar regolith, the pulverized rocky surface of the Moon, can be used as concrete to make structures. Spacecraft have identified large deposits of water at the Moon’s poles, in its permanently shadowed craters. As with Mercury, these would make ideal locations for colonies.
Here, a surface exploration crew begins its investigation of a typical, small lava tunnel, to determine if it could serve as a natural shelter for the habitation modules of a Lunar Base. Credit: NASA’s Johnson Space Center
Our spacecraft have also captured images of openings to underground lava tubes on the surface of the Moon. Some of these could be gigantic, even kilometers high. You could fit massive cities inside some of these lava tubes, with room to spare.
Helium-3 from the Sun rains down on the surface of the Moon, deposited by the Sun’s solar wind, which could be mined from the surface and provide a source of fuel for lunar fusion reactors. This abundance of helium could be exported to other places in the Solar System.
The far side of the Moon is permanently shadowed from Earth-based radio signals, and would make an ideal location for a giant radio observatory. Telescopes of massive size could be built in the much lower lunar gravity.
We talked briefly about an Earth-based space elevator, but an elevator on the Moon makes even more sense. With the lower gravity, you can lift material off the surface and into lunar orbit using cables made of materials we can manufacture today, such as Zylon or Kevlar.
One of the greatest threats on the Moon is the dusty regolith itself. Without any kind of weathering on the surface, these dust particles are razor sharp, and they get into everything. Lunar colonists will need very strict protocols to keep the lunar dust out of their machinery, and especially out of their lungs and eyes, otherwise it could cause permanent damage.
Artist’s impression of a Near-Earth Asteroid passing by Earth. Credit: ESA
Although the vast majority of asteroids in the Solar System are located in the main asteroid belt, there are still many asteroids orbiting closer to Earth. These are known as the Near Earth Asteroids, and they’ve been the cause of many of Earth’s great extinction events.
These asteroids are dangerous to our planet, but they’re also an incredible resource, located close to our homeworld.
The amount of velocity it takes to get to some of these asteroids is very low, which means travel to and from these asteroids takes little energy. Their low gravity means that extracting resources from their surface won’t take a tremendous amount of energy.
And once the orbits of these asteroids are fully understood, future colonists will be able to change the orbits using thrusters. In fact, the same system they use to launch minerals off the surface would also push the asteroids into safer orbits.
These asteroids could be hollowed out, and set rotating to provide artificial gravity. Then they could be slowly moved into safe, useful orbits, to act as space stations, resupply points, and permanent colonies.
There are also gravitationally stable points at the Sun-Earth L4 and L5 Lagrange Points. These asteroid colonies could be parked there, giving us more locations to live in the Solar System.
Mosaic of the Valles Marineris hemisphere of Mars, similar to what one would see from orbital distance of 2500 km. Credit: NASA/JPL-Caltech
The future of humanity will include the colonization of Mars, the fourth planet from the Sun. On the surface, Mars has a lot going for it. A day on Mars is only a little longer than a day on Earth. It receives sunlight, unfiltered through the thin Martian atmosphere. There are deposits of water ice at the poles, and under the surface across the planet.
Martian ice will be precious, harvested from the planet and used for breathable air, rocket fuel and water for the colonists to drink and grow their food. The Martian regolith can be used to grow food. It does have have toxic perchlorates in it, but that can just be washed out.
The lower gravity on Mars makes it another ideal place for a space elevator, ferrying goods up and down from the surface of the planet.
The area depicted is Noctis Labyrinthus in the Valles Marineris system of enormous canyons. The scene is just after sunrise, and on the canyon floor four miles below, early morning clouds can be seen. The frost on the surface will melt very quickly as the Sun climbs higher in the Martian sky. Credit: NASA
Unlike the Moon, Mars has a weathered surface. Although the planet’s red dust will get everywhere, it won’t be toxic and dangerous as it is on the Moon.
Like the Moon, Mars has lava tubes, and these could be used as pre-dug colony sites, where human Martians can live underground, protected from the hostile environment.
Mars has two big problems that must be overcome. First, the gravity on Mars is only a third that of Earth’s, and we don’t know the long term impact of this on the human body. It might be that humans just can’t mature properly in the womb in low gravity.
Researchers have proposed that Mars colonists might need to spend large parts of their day on rotating centrifuges, to simulate Earth gravity. Or maybe humans will only be allowed to spend a few years on the surface of Mars before they have to return to a high gravity environment.
The second big challenge is the radiation from the Sun and interstellar cosmic rays. Without a protective magnetosphere, Martian colonists will be vulnerable to a much higher dose of radiation. But then, this is the same challenge that colonists will face anywhere in the entire Solar System.
That radiation will cause an increased risk of cancer, and could cause mental health issues, with dementia-like symptoms. The best solution for dealing with radiation is to block it with rock, soil or water. And Martian colonists, like all Solar System colonists will need to spend much of their lives underground or in tunnels carved out of rock.
Two astronauts explore the rugged surface of Phobos. Mars, as it would appear to the human eye from Phobos, looms on the horizon. The mother ship, powered by solar energy, orbits Mars while two crew members inside remotely operate rovers on the Martian surface. Credit: NASA/Pat Rawlings (SAIC)
In addition to Mars itself, the Red Planet has two small moons, Phobos and Deimos. These will serve as ideal places for small colonies. They’ll have the same low gravity as asteroid colonies, but they’ll be just above the gravity well of Mars. Ferries will travel to and from the Martian moons, delivering fresh supplies and sending Martian goods out to the rest of the Solar System.
We’re not certain yet, but there are good indicators these moons might have ice inside them, if so that is an excellent source of fuel and could make initial trips to Mars much easier by allowing us to send a first expedition to those moons, who then begin producing fuel to be used to land on Mars and to leave Mars and return home.
According to Elon Musk, if a Martian colony can reach a million inhabitants, it’ll be self-sufficient from Earth or any other world. At that point, we would have a true, Solar System civilization.
Now, continue on to the other half of this article, written by Isaac Arthur, where he talks about what it will take to colonize the outer Solar System. Where water ice is plentiful but solar power is feeble. Where travel times and energy require new technologies and techniques to survive and thrive.
Okay, so this article is Colonizing the Outer Solar System, and is actually part 2 of our team up with Fraser Cain of Universe Today, who looked at colonizing the inner solar system. You might want jump over there now and watch that part first, if you are coming in from having seen part 1, welcome, it is great having you here.
Without further ado let us get started. There is no official demarcation between the inner and outer solar system but for today we will be beginning the outer solar system at the Asteroid Belt.
Artist concept of the asteroid belt. Credit: NASA
The Asteroid Belt is always of interest to us for colonization. We have talked about mining them before if you want the details on that but for today I’ll just remind everyone that there are very rich in metals, including precious metals like gold and platinum, and that provides all the motivation we need to colonize them. We have a lot of places to cover so we won’t repeat the details on that today.
You cannot terraform asteroids the way you could Venus or Mars so that you could walk around on them like Earth, but in every respect they have a lot going for them as a candidate. They’ve got plenty for rock and metal for construction, they have lots of the basic organic elements, and they even have some water. They also get a decent amount of sunlight, less than Mars let alone Earth, but still enough for use as a power source and to grow plants.
But they don’t have much gravity, which – pardon the pun – has its ups and downs. There just isn’t much mass in the Belt. The entire thing has only a small fraction of the mass of our moon, and over half of that is in the four biggest asteroids, essentially dwarf planets in their own right. The remainder is scattered over millions of asteroids. Even the biggest, Ceres, is only about 1% of 1% of Earth’s mass, has a surface gravity of 3% Earth-normal, and an escape velocity low enough most model rockets could get into orbit. And again, it is the biggest, most you could get away from by jumping hard and if you dropped an object on one it might take a few minutes to land.
Don’t blink… an artist’s conception of an asteroid blocking out a distant star. Image credit: NASA.
You can still terraform one though, by definition too. The gentleman who coined the term, science fiction author Jack Williamson, who also coined the term genetic engineering, used it for a smaller asteroid just a few kilometers across, so any definition of terraforming has to include tiny asteroids too.
Of course in that story it’s like a small planet because they had artificial gravity, we don’t, if we want to fake gravity without having mass we need to spin stuff around. So if we want to terraform an asteroid we need to hollow it out and fill it with air and spin it around.
Of course you do not actually hollow out the asteroid and spin it, asteroids are loose balls of gravel and most would fly apart given any noticeable spin. Instead you would hollow it out and set a cylinder spinning inside it. Sort of like how a good thermos has an outside container and inside one with a layer of vacuum in between, we would spin the inner cylinder.
You wouldn’t have to work hard to hollow out an asteroid either, most aren’t big enough to have sufficient gravity and pressure to crush an empty beer can even at their center. So you can pull matter out from them very easily and shore up the sides with very thin metal walls or even ice. Or just have your cylinder set inside a second non-spinning outer skin or superstructure, like your washer or dryer.
You can then conduct your mining from the inside, shielded from space. You could ever pressurize that hollowed out area if your spinning living area was inside its own superstructure. No gravity, but warmth and air, and you could get away with just a little spin without tearing it apart, maybe enough for plants to grow to normally.
It should be noted that you can potentially colonize even the gas giants themselves, even though our focus today is mostly on their moons. That requires a lot more effort and technology then the sorts of colonies we are discussing today, Fraser and I decided to keep things near-future and fairly low tech, though he actually did an article on colonizing Jupiter itself last year that was my main source material back before got to talking and decided to do a video together.
Jupiter with Io and Ganymede taken by amateur astronomer Damian Peach. Credit: NASA / Damian Peach
Hydrogen is plentiful on Jupiter itself and floating refineries or ships that fly down to scoop it up might be quite useful, but again today we are more interested in its moons. The biggest problem with colonizing the moons of Jupiter is all the radiation the planet gives off.
Europa is best known as a place where the surface is covered with ice but beneath it is thought to be a vast subsurface ocean. It is the sixth largest moon coming right behind our own at number five and is one of the original four moons Galileo discovered back in 1610, almost two centuries before we even discovered Uranus, so it has always been a source of interest. However as we have discovered more planets and moons we have come to believe quite a few of them might also have subsurface oceans too.
Now what is neat about them is that water, liquid water, always leaves the door open to the possibility of life already existing there. We still know so little about how life originally evolved and what conditions permit that to occur that we cannot rule out places like Europa already having their own plants and animals swimming around under that ice.
They probably do not and obviously we wouldn’t want to colonize them, beyond research bases, if they did, but if they do not they become excellent places to colonize. You could have submarine cities in such places floating around in the sea or those buried in the surface ice layer, well shielded from radiation and debris. The water also geysers up to the surface in some places so you can start off near those, you don’t have to drill down through kilometers of ice on day one.
Water, and hydrogen, are also quite uncommon in the inner solar system so having access to a place like Europa where the escape velocity is only about a fifth of our own is quite handy for export. Now as we move on to talk about moons a lot it is important to note that when I say something has a fifth of the escape velocity of Earth that doesn’t mean it is fives time easier to get off of. Energy rises with the square of velocity so if you need to go five times faster you need to spend 5-squared or 25 times more energy, and even more if that place has tons of air creating friction and drag, atmospheres are hard to claw your way up through though they make landing easier too. But even ignoring air friction you can move 25 liters of water off of Europa for every liter you could export from Earth and even it is a very high in gravity compared to most moons and comets. Plus we probably don’t want to export lots of water, or anything else, off of Earth anyway.
Artist’s concept of Trojan asteroids, small bodies that dominate our solar system. Credit: NASA
We should start by noting two things. First, the Asteroid Belt is not the only place you find asteroids, Jupiter’s Trojan Asteroids are nearly as numerous, and every planet, including Earth, has an equivalent to Jupiter’s Trojan Asteroids at its own Lagrange Points with the Sun. Though just as Jupiter dwarfs all the other planets so to does its collection of Lagrangian objects. They can quite big too, the largest 624 Hektor, is 400 km across, and has a size and shape similar to Pennsylvania.
And as these asteroids are at stable Lagrange Points, they orbit with Jupiter but always ahead and behind it, making transit to and from Jupiter much easier and making good waypoints.
Before we go out any further in the solar system we should probably address how you get the energy to stay alive. Mars is already quite cold compared to Earth, and the Asteroids and Jupiter even more so, but with thick insulation and some mirrors to bounce light in you can do fairly decently. Indeed, sunlight out by Jupiter is already down to just 4% of what Earth gets, meaning at Jovian distances it is about 50 W/m²
That might not sound like much but it is actually almost a third of what average illumination is on Earth, when you factor in atmospheric reflection, cloudy days, nighttime, and higher, colder latitudes. It is also a good deal brighter than the inside of most well-lit buildings, and is enough for decently robust photosynthesis to grow food. Especially with supplemental light from mirrors or LED growth lamps.
But once you get out to Saturn and further that becomes increasingly impractical and a serious issue, because while food growth does not show up on your electric bill it is what we use virtually all our energy for. Closer in to the sun we can use solar panels for power and we do not need any power to grow food. As we get further out we cannot use solar and we need to heat or cold habitats and supply lighting for food, so we need a lot more power even as our main source dries up.
So what are our options? Well the first is simple, build bigger mirrors. A mirror can be quite large and paper thin after all. Alternatively we can build those mirrors far away, closer to the sun, and and either focus them on the place we want illuminated or send an energy beam, microwaves perhaps or lasers, out to the destination to supply energy.
We also have the option of using fission, if we can find enough Uranium or Thorium. There is not a lot of either in the solar system, in the area of about one part per billion, but that does amount to hundreds of trillions of tons, and it should only take a few thousand tons a year to supply Earth’s entire electric grid. So we would be looking at millions of years worth of energy supply.
Of course fusion is even better, particularly since hydrogen becomes much more abundant as you get further from the Sun. We do not have fusion yet, but it is a technology we can plan around probably having inside our lifetimes, and while uranium and thorium might be counted in parts per billion, hydrogen is more plentiful than every other element combines, especially once you get far from the Sun and Inner Solar System.
So it is much better power source, an effectively unlimited one except on time scales of billions and trillion of years. Still, if we do not have it, we still have other options. Bigger mirrors, beaming energy outwards from closer to the Sun, and classic fission of Uranium and Thorium. Access to fusion is not absolutely necessary but if you have it you can unlock the outer solar system because you have your energy supply, a cheap and abundant fuel supply, and much faster and cheaper spaceships.
Of course hydrogen, plain old vanilla hydrogen with one proton, like the sun uses for fusion, is harder to fuse than deuterium and may be a lot longer developing, we also have fusion using Helium-3 which has some advantages over hydrogen, so that is worth keeping in mind as well as we proceed outward.
Since NASA’s Cassini spacecraft arrived at Saturn, the planet’s appearance has changed greatly. This view shows Saturn’s northern hemisphere in 2016, as that part of the planet nears its northern hemisphere summer solstice in May 2017. Image credit: NASA/JPL-Caltech/Space Science Institute.
Okay, let’s move on to Saturn, and again our focus is on its moons more than the planet itself. The biggest of those an the most interesting for colonization is Titan.
Titan is aptly named, this titanic moon contains more mass than than all of Saturn’s sixty or so other moons and by an entire order of magnitude at that. It is massive enough to hold an atmosphere, and one where the surface pressure is 45% higher than here on Earth. Even though Titan is much smaller than Earth, its atmosphere is about 20% more massive than our own. It’s almost all nitrogen too, even more than our own atmosphere, so while you would need a breather mask to supply oxygen and it is also super-cold, so you’d need a thick insulated suit, it doesn’t have to be a pressure suit like it would on Mars or almost anyplace else.
There’s no oxygen in the atmosphere, what little isn’t nitrogen is mostly methane and hydrogen, but there is plenty of oxygen in the ice on Titan which is quite abundant. So it has everything we need for life except energy and gravity. At 14% of earth normal it is probably too low for people to comfortably and safely adapt to, but we’ve already discussed ways of dealing with that. It is low enough that you could probably flap your arms and fly, if you had wing attached.
On the left is TALISE (Titan Lake In-situ Sampling Propelled Explorer), the ESA proposal. This would have it’s own propulsion, in the form of paddlewheels. Credit: bisbos.com
It needs some source of energy though, and we discussed that. Obviously if you’ve got fusion you have all the hydrogen you need, but Titan is one of those places we would probably want to colonize early on if we could, it is something you need a lot of to terraform other places, and is also rich in a lot of the others things we want. So we often think of it as a low-tech colony since it is one we would want early on.
In an scenario like that it is very easy to imagine a lot of local transit between Titan and its smaller neighboring moons, which are more rocky and might be easier to dig fissile materials like Uranium and Thorium out of. You might have a dozen or so small outposts on neighboring moons mining fissile materials and other metals and a big central hub on Titan they delivered that too which also exported Nitrogen to other colonies in the solar system.
Moving back and forth between moons is pretty easy, especially since things landing on Titan can aerobrake quite easily, whereas Titan itself has a pretty strong gravity well and thick atmosphere to climb out of but is a good candidate for a space elevator, since it requires nothing more sophisticated than a Lunar Elevator on our own moon and has an abundant supply of the materials needed to make Zylon for instance, a material strong enough to make an elevator there and which we can mass manufacture right now.
Titan might be the largest and most useful of Saturn’s moons, but again it isn’t the only one and not all of the other are just rocks for mining. At last count it has over sixty and many of them quite large. One of those, Enceladus, Saturn’s sixth largest moon, is a lot like Jupiter’s Moon Europa, in that we believe it has a large and thick subsurface ocean. So just like Europa it is an interesting candidate for Colonization. So Titan might be the hub for Saturn but it wouldn’t be the only significant place to colonize.
While Saturn is best known for its amazing rings, they tend to be overlooked in colonization. Now those rings are almost all ice and in total mass about a quarter as much as Enceladus, which again is Saturn’s Sixth largest moon, which is itself not even a thousandth of the Mass of Titan.
In spite of that the rings are not a bad place to set up shop. Being mostly water, they are abundant in hydrogen for fusion fuel and have little mass individually makes them as easy to approach or leave as an asteroid. Just big icebergs in space really, and there are many moonlets in the rings that can be as large as half a kilometer across. So you can burrow down inside one for protection from radiation and impacts and possibly mine smaller ones for their ice to be brought to places where water is not abundant.
In total those rings, which are all frozen water, only mass about 2% of Earth’s oceans, and about as much as the entire Antarctic sheet. So it is a lot of fresh water that is very easy to access and move elsewhere, and ice mines in the rings of Saturn might be quite useful and make good homes. Living inside an iceball might not sound appealing but it is better than it sounds like and we will discuss that more when we reach the Kupier Belt.
Uranus and Neptune, the Solar System’s ice giant planets. Credit: Wikipedia Commons
But first we still have two more planets to look at, Uranus and Neptune.
Uranus, and Neptune, are sometimes known as Ice Giants instead of Gas Giants because it has a lot more water. It also has more ammonia and methane and all three get called ices in this context because they make up most of the solid matter when you get this far out in the solar system.
While Jupiter is over a thousand times the mass of Earth, Uranus weighs in at about 15 times the Earth and has only about double the escape velocity of Earth itself, the least of any of the gas giants, and it’s strange rotation, and its strange tilt contributes to it having much less wind than other giants. Additionally the gravity is just a little less than Earth’s in the atmosphere so we have the option for floating habitats again, though it would be a lot more like a submarine than a hot air balloon.
Like Venus, Uranus has very long days, at least in terms of places receiving continual sunlight, the poles get 42 years of perpetual sunlight then 42 of darkness. Sunlight being a relative term, the light is quite minimal especially inside the atmosphere. The low wind in many places makes it a good spot for gas extraction, such as Helium-3, and it’s a good planet to try to scoop gas from or even have permanent installations.
Now Uranus has a large collection of moons as well, useful and colonizable like the other moons we have looked at, but otherwise unremarkable beyond being named for characters from Shakespeare, rather than the more common mythological names. None have atmospheres though there is a possibility Oberon or Titania might have subsurface oceans.
Neptune makes for a brief entry, it is very similar to Uranus except it has the characteristically high winds of gas giants that Uranus’s skewed poles mitigate, meaning it has no advantages over Uranus and the disadvantages of high wind speeds everywhere and being even further from the Sun. It too has moons and one of them, Triton, is thought to have subsurface oceans as well. Triton also presumably has a good amount of nitrogen inside it since it often erupts geysers of nitrogen from its surface.
Neptune’s largest moon Triton photographed on August 25, 1989 by Voyager 2. Credit: NASA
Triton is one of the largest moons in the solar system, coming in seventh just after our Moon, number 5, and Europa at number 6. Meaning that were it not a moon it would probably qualify as a Dwarf Planet and it is often thought Pluto might be an escaped moon Neptune. So Triton might be one that didn’t escape, or didn’t avoid getting captured. In fact there are an awful lot of bodies in this general size range and composition wandering about in the outer regions of our solar system as we get out into the Kuiper Belt.
Pluto and its cohorts in the icy-asteroid-rich Kuiper Belt beyond the orbit of Neptune. Credit: NASA
The Kuiper Belt is one of those things that has a claim on the somewhat arbitrary and hazy boundary marking the edge of the Solar System. It extends from out past Neptune to beyond Pluto and contains a good deal more mass than the asteroid Belt. It is where a lot of our comets come from and while there is plenty of rocks out there they tend to be covered in ice. In other words it is like our asteroid belt only there’s more of it and the one thing the belt is not very abundant in, water and hydrogen in general, is quite abundant out there. So if you have a power source life fusion they can be easily terraformed and are just as attractive as a source of minerals as the various asteroids and moons closer in.
Discovered in 2005, Makemake, a Kuiper Belt Object (KBO) has . Credit: NASA
We mentioned the idea of living inside hollowed out asteroids earlier and you can use the same trick for comets. Indeed you could shape them to be much bigger if you like, since they would be hollow and ice isn’t hard to move and shape especially in zero gravity. Same trick as before, you place a spinning cylinder inside it. Not all the objects entirely ice and indeed your average comet is more a frozen ball of mud then ice with rocky cores. We think a lot of near Earth Asteroids are just leftover comets. So they are probably pretty good homes if you have fusion, lots of fuel and raw materials for both life and construction.
This is probably your cheapest interstellar spacecraft too, in terms of effort anyway. People often talk about re-directing comets to Mars to bring it air and water, but you can just as easily re-direct it out of the solar system entirely. Comets tend to have highly eccentric orbits, so if you capture one when it is near the Sun you can accelerate it then, actually benefiting from the Oberth Effect, and drive it out of the solar system into deep space. If you have a fusion power source to live inside one then you also have an interstellar spaceship drive, so you just carve yourself a small colony inside the comet and head out into deep space.
You’ve got supplies that will last you many centuries at least, even if it were home to tens of thousand of people, and while we think of smaller asteroids and comets as tiny, that’s just in comparison to planets. These things tend to be the size of mountain so there is plenty of living space and a kilometer of dirty ice between you and space makes a great shield against even the kinds of radiation and collisions you can experience at relativistic speeds.
Artists’ impression of the Kuiper belt and Oort cloud. Credit: NASA/JPL
Now the Oort Cloud is much like the Kupier Belt but begins even further out and extends out probably an entire light year or more. We don’t have a firm idea of its exact dimensions or mass, but the current notion is that it has at least several Earth’s worth of mass, mostly in various icy bodies. These will be quite numerous, estimates usually assumes at least trillion icy bodies a kilometer across or bigger, and even more smaller ones. However the volume of space is so large that those kilometer wide bodies might each be a around a billion kilometers distant from neighbors, or about a light hour. So it is spread out quite thinly, and even the inner edge is about 10 light days away.
That means that from a practical standpoint there is no source of power out there, the sun is simply too diffuse for even massive collections of mirrors and solar panels to be of use. It also means light-speed messages home or to neighbors are quite delayed. So in terms of communication it is a lot more like pre-modern times in sparsely settled lands where talking with your nearest neighbors might require an hour long walk over to their farm, and any news from the big cities might take months to percolate out to you.
There’s probably uranium and thorium out there to be found, maybe a decent amount of it, so fission as a power source is not ruled out. If you have fusion instead though each of these kilometer wide icy bodies is like a giant tank of gasoline, and as with the Kupier Belt, ice makes a nice shield against impacts and radiation.
And while there might be trillions of kilometer wide chunks of ice out there, and many more smaller bodies, you would have quite a few larger ones too. There are almost certainly tons of planets in the Pluto size-range out these, and maybe even larger ones. Even after the Oort cloud you would still have a lot of these deep space rogue planets which could bridge the gap to another solar system’s Oort Cloud. So if you have fusion you have no shortage of energy, and could colonize trillions of these bodies. There probably is a decent amount of rock and metal out there too, but that could be your major import/export option shipping home ice and shipping out metals.
That’s the edge of the Solar System so that’s the end of this article. If you haven’t already read the other half, colonizing the inner Solar System, head on over now.
Look how pretty. This will be the scene from your yard, apartment window or driving west along a freeway Tuesday evening about 45 minutes after sundown. Saturn and the Moon will be in conjunction about 3 degrees apart with Venus 6 degrees to the southeast of the crescent. Source: Stellarium
I love easy and bright. While I often spend time seeking faint nebulae and wandering comets, there’s nothing like just looking up and seeing a beautiful scene aglow in the night sky. No binoculars or telescope needed. That’s exactly what will happen Tuesday November 2, when an attractive crescent Moon will join Saturn and Venus at dusk in the southwestern sky.
The Supermoon of March 19, 2011 (right), compared to an average moon of December 20, 2010 (left). November’s Supermoon will be 14% bigger and 30% brighter than a regular Full Moon. Credit: Marco Langbroek / Wikimedia Commons
What a fine threesome they’ll make: Venus the white-hot spark shining at magnitude –4.0; Saturn a mellow magnitude +0.5, some 20 times fainter and the Moon a fingernail crescent above them both. The Moon will be just two days past apogee, the furthest point in its orbit from Earth. Does it look a little smaller than the usual crescent? If you’re a keen watcher of crescents, you just might notice the difference.
In less than two weeks, on November 14, the crescent will have waxed to full, swung around to the opposite end of its orbit, where it will be at perigee, its closest point to Earth. When a Full Moon occurs at perigee, we call it a Supermoon because it’s closer and correspondingly bigger and brighter than a typical Full Moon.
For a variety of reasons, the November Supermoon will come exceptionally close to Earth, the closest one in 70 years as a matter of fact. The last time Earth and Moon embraced each other so tightly was January 26, 1948, the year baseball great Babe Ruth died. But I’m getting ahead of myself. We’ll have much more on the Supermoon soon!
This photo shows the contrast between the bright, sunlit crescent and the ghostly earth-lit Moon. Several prominent craters are identified. Credit: Bob King
Tuesday night you have the pleasure of an eye-catching crescent filled with darkly luminous earthshine, sunlight reflected off our jolly blue and white globe into space that reflects from the Moon and back to Earth. Being twice reflected, the returning light is feeble, giving the Moon a haunted look.
The phases of the Moon and Earth are complementary; when one’s a crescent, the other’s nearly full. Credit: Bob King, Source: Stellarium
Crescent phase is when earthshine is brightest. Why? Phases of Earth and Moon are complementary — when we see a crescent, an astronaut on the Moon would look back to see a nearly Full Earth in the sky. As you’ve already guessed, a Full Earth reflects a great deal more light than a half or crescent. Be sure to point your binoculars at the earth-lit Moon; the contrast of dusky earthlight adjacent to the sunlit crescent gives the scene a striking 3D look.
And if your glass can magnify ten times or more, you’ll get a sneak preview of several of the dark lunar seas or maria in the smoky light. Seas that will by and by ease into sunlight as the lunar terminator, the line separating day from night, rolls ever westward.
Through a small telescope, Venus appears three-quarters full in waning gibbous phase. Saturn’s rings are still tipped wide open, and its brightest moon, Titan, should be easy to spot Tuesday night in a small telescope. Appearances are shown for Nov. 2. North is up and west to the right. Source: Stellarium
Have a small telescope? This may be one of your last easy chances at seeing the planet Saturn before it’s gobbled up by the western horizon. The ringed one has been sinking westward the past couple months and will soon be in conjunction with the Sun. I hate to see a good planet go, that’s why I’m happy to share that Venus will be with us a long, long time. Watch for this most brilliant of planets to rise higher in the southwestern sky as we approach Christmas and then swing to the north through early winter before dropping out of the evening sky in March 2017.
Thank you Venus for lighting our path on the snowy nights that lie ahead!
*** If you’d like learn more about how to find the planets, check out my new book, Night Sky with the Naked Eye. It covers all the wonderful things you can see in the night sky without special equipment. The book publishes on Nov. 8, but you can pre-order it right now at these online stores. Just click an icon to go to the site of your choice – Amazon, Barnes & Noble or Indiebound. It’s currently available at the first two outlets for a very nice discount:
Venus and Jupiter at dusk over Australia's Outback on June 27, 2015. Credit: Joseph Brimacombe
The internet is great, isn’t it?
You can post anything you want on the internet, and if people like the sound of it, they spread it. It doesn’t make any difference if it’s true or not. We’re not born fact checkers and skeptics, are we?
Pretty soon, before you know it, it’s gone viral. Then it becomes its own sensation, and people who don’t even believe it start reporting it. Never is this more true than with hoaxes.
The latest hoax is the “15 Days of Darkness in November” thing that’s going around. Everyone’s on the bandwagon.
The 15 days hoax is not new. It made an appearance last year, and was thoroughly debunked. And of course, there wasn’t 15 day of darkness last year, was there? (Unless NASA covered it up!)
It’s here again this year, and will be debunked again, and will probably be here next year, too.
The whole thing started at a site that will remain linkless, and caught on from there. This is what the site reported:
“NASA has confirmed that the Earth will experience 15 days of total darkness between November 15 and November 29, 2015. The event, according to NASA, hasn’t occurred in over 1 Million years.”
Of course, NASA never said any such thing.
Here is supposedly what will happen to cause this calamity. Try and follow along with the nonsensical foolishness.
During the conjunction between Venus and Jupiter on October 26, light from Venus would cause gases in Jupiter to heat up. The heated gasses will cause a large amount of hydrogen to be released into space. The gases will reach the Sun and trigger a massive explosion on the surface of the star, heating it to 9,000 degrees Kelvin. The heat of the explosion would then cause the Sun to emit a blue color.
The dull blue color will last for 15 days during which the Earth will be thrown into darkness.
Where to begin? Let’s start with conjunctions.
Conjunctions are mostly just visual phenomena. The fact that two things in the sky look closer together from our point of view on Earth doesn’t mean that they’re that close together. In fact, even when Jupiter and Venus are in conjunction, they can still be over 800 million km apart. For perspective, the Sun and the Earth are about 150 million km apart.
So, as the hoax goes, at that great distance, light from Venus will cause gases on Jupiter to heat up. News Flash: the light from the Sun is far more intense than light from Venus could ever be, and it doesn’t heat up the gases on Jupiter. In fact, any light from Venus that makes it to Jupiter is just reflected sunlight anyway.
The Moon and this dead tree are in conjunction. This will cause the Martian Pyramids to vibrate harmonically. These vibrations will shake the walls of the movie studio where the Moon landing was faked, causing it to collapse. Image: Evan Gough
The hoax gets more outrageous as it goes along. These supposed heated gases then escape from Jupiter into space, and head for the Sun. But Jupiter is enormous and has enormous gravitational pull. How are any gases going to escape Jupiter’s overpowering gravity? Answer: they can’t and they won’t.
Then, these gases supposedly strike the Sun, and trigger a massive explosion on the Sun’s surface, which turn the Sun blue and plunges the Earth into darkness. Not blueness, which I could understand, but darkness.
This is absurd, of course. The Sun dominates the planets in a one-way relationship, and nothing the planets ever do could change that. No escaped gases from Jupiter would ever strike the Sun.
Jupiter is puny and insignificant compared to the Sun. And it’s also hundreds of millions of kilometers away. How is a puny puff of hydrogen from Jupiter supposed to darken the Sun? Image: NASA/SDO
Nothing Jupiter does can affect the Sun. Jupiter is, on average, 778 million km from the Sun. Jupiter could change places with Venus, and the Sun would keep shining normally. Jupiter could explode completely and the Sun would go on shining normally. Jupiter could put on a big red nose and some clown shoes, and the Sun would remain unaffected.
The Sun is a giant atom-crushing machine 1000 times more massive than Jupiter. The massive wall of energy and solar wind that comes from the Sun slams into Jupiter, and completely overwhelms anything Jupiter can do to the Sun. It’s just the way it is. It’s just the way it will always be.
Like the faked Moon landing hoax, and the Nibiru/Planet X hoax, this 15 days of darkness meme just keeps coming around. There may be no end to it.
It’s annoying, for sure, but maybe there’s a silver lining. Maybe some people reading about this supposed calamity will enter the word “conjunction” into a search engine, and begin their own personal journey of learning how the universe works.
Image taken by a crew member of Expedition 13 from the ISS, showing the eruption of Cleveland Volcano, Aleutian Islands, Alaska. Credit: NASA
A volcano is an impressive sight. When they are dormant, they loom large over everything on the landscape. When they are active, they are a destructive force of nature that is without equal, raining fire and ash down on everything in site. And during the long periods when they are not erupting, they can also be rather beneficial to the surrounding environment.
But just what causes volcanoes? When it comes to our planet, they are the result of active geological forces that have shaped the surface of the Earth over the course of billions of years. And interestingly enough, there are plenty of examples of volcanoes on other bodies within our Solar System as well, some of which put those on Earth to shame!
Definition:
By definition, a volcano is a rupture in the Earth’s (or another celestial body’s) crust that allows hot lava, volcanic ash, and gases to escape from a magma chamber located beneath the surface. The term is derived from Vulcano, a volcanically-active island located of the coast of Italy who’s name in turn comes from the Roman god of fire (Vulcan).
Artist’s illustration of the Earth’s Tectonic Plates. Credit: msnucleus.org
On Earth, volcanoes are the result of the action between the major tectonic plates. These sections of the Earth’s crust are rigid, but sit atop the relatively viscous upper mantle. The hot molten rock, known as magma, is forced up to the surface – where it becomes lava. In short, volcanoes are found where tectonic plates are diverging or converging – such as the Mid-Atlantic Ridge or the Pacific Ring of Fire – which causes magma to be forced to the surface.
Volcanoes can also form where there is stretching and thinning of the crust’s interior plates, such as in the the East African Rift and the Rio Grande Rift in North America. Volcanism can also occur away from plate boundaries, where upwelling magma is forced up into brittle sections of the crust, forming volcanic islands – such as the Hawaiian islands.
Erupting volcanoes pose many hazards, and not just to the surrounding countryside. In their immediate vicinity, hot, flowing lava can cause extensive damage to the environment, property, and endanger lives. However, volcanic ash can cause far-reaching damage, raining sulfuric acid, disrupting air travel, and even causing “volcanic winters” by obscuring the Sun (thus triggering local crop failures and famines).
Types of Volcanoes:
There are four major types of volcanoes – cinder cone, composite and shield volcanoes, and lava domes. Cinder cones are the simplest kind of volcano, which occur when magma is ejected from a volcanic vent. The ejected lava rains down around the fissure, forming an oval-shaped cone with a bowl-shaped crater on top. They are typically small, with few ever growing larger than about 300 meters (1,000 feet) above their surroundings.
Paricutin, an example of a cinder cone volcano. Credit: USGS
Composite volcanoes (aka. stratovolcanoes) are formed when a volcano conduit connects a subsurface magma reservoir to the Earth’s surface. These volcanoes typically have several vents that cause magma to break through the walls and spew from fissures on the sides of the mountain as well as the summit.
These volcanoes are known for causing violent eruptions. And thanks to all this ejected material, these volcanoes can grow up to thousands of meters tall. Examples include Mount Rainier (4,392 m; 14,411 ft), Mount Fuji (3,776 m; 12,389 ft), Mount Cotopaxi (5,897 m; 19,347 ft) and Mount Saint Helens (2,549 mm; 8,363 ft).
Shield volcanoes are so-named because of their large, broad surfaces. With these types of volcanoes, the lava that pours forth is thin, allowing it to travel great distances down the shallow slopes. This lava cools and builds up slowly over time, with hundreds of eruptions creating many layers. They are therefore not likely to be catastrophic. Some of the best known examples are those that make up the Hawaiian Islands, especially Mauna Loa and Mauna Kea.
Volcanic or lava domes are created by small masses of lava which are too viscous to flow very far. Unlike shield volcanoes, which have low-viscosity lava, the slow-moving lava simply piles up over the vent. The dome grows by expansion over time, and the mountain forms from material spilling off the sides of the growing dome. Lava domes can explode violently, releasing a huge amount of hot rock and ash.
Artist’s impression of a what lies beneath the Yellowstone volcano. Credit: Hernán Cañellas/National Geographic
Volcanoes can also be found on the ocean floor, known as submarine volcanoes. These are often revealed through the presence of blasting steam and rocky debris above the ocean’s surface, though the pressure of the ocean’s water can often prevent an explosive release.
In these cases, lava cools quickly on contact with ocean water, and forms pillow-shaped masses on the ocean floor (called pillow lava). Hydrothermal vents are also common around submarine volcano, which can support active and peculiar ecosystems because of the energy, gases and minerals they release. Over time, the formations created by submarine volcanoes may become so large that they become islands.
Volcanoes can also developed under icecaps, which are known as subglacial volcanoes. In these cases, flat lava flows on top of pillow lava, which results from lava quickly cooling upon contact with ice. When the icecap melts, the lava on top collapses, leaving a flat-topped mountain. Very good examples of this type of volcano can be seen in Iceland and British Columbia, Canada.
Examples on Other Planets:
Volcanoes can be found on many bodies within the Solar System. Examples include Jupiter’s moon Io, which periodically experiences volcanic eruptions that reach up to 500 km (300 mi) into space. This volcanic activity is caused by friction or tidal dissipation produced in Io’s interior, which is responsible for melting a significant amount of Io’s mantle and core.
Model of the possible interior composition of Io with various features labelled. Credit: Wikipedia Commons/Kelvinsong
It’s colorful surface (orange, yellow, green, white/grey, etc.) shows the presence of sulfuric and silicate compounds, which were clearly deposited by volcanic eruptions. The lack of impact craters on its surface, which is uncommon on a Jovian moon, is also indicative of surface renewal.
Mars has also experienced intense volcanic activity in its past, as evidenced by Olympus Mons – the largest volcano in the Solar System. While most of its volcanic mountains are extinct and collapsed, the Mars Express spacecraft observed evidence of more recent volcanic activity, suggesting that Mars may still be geologically active.
Much of Venus’ surface has been shaped by volcanic activity as well. While Venus has several times the number of Earth’s volcanoes, they were believed to all be extinct. However, there is a multitude of evidence that suggests that there may still be active volcanoes on Venus which contribute to its dense atmosphere and runaway Greenhouse Effect.
For instance, during the 1970s, multiple Soviet Venera missions conducted surveys of Venus. These missions obtained evidence of thunder and lightning within the atmosphere, which may have been the result of volcanic ash interacting with the atmosphere. Similar evidence was gathered by the ESA’s Venus Express probe in 2007.
3-D perspective of the Venusian volcano, Maat Mons generated from radar data from NASA’s Magellan mission. Credit: NASA/JPL
This same mission observed transient localized infrared hot spots on the surface of Venus in 2008 and 2009, specifically in the rift zone Ganis Chasma – near the shield volcano Maat Mons. The Magellan probe also noted evidence of volcanic activity from this mountain during its mission in the early 1990s, using radar-sounding to detect ash flows near the summit.
Cryovolcanism:
In addition to “hot volcanoes” that spew molten rock, there are also cryovolcanoes (aka. “cold volcanoes”). These types of volcanoes involve volatile compounds – i.e. water, methane and ammonia – instead of lava breaking through the surface. They have been observed on icy bodies in the Solar System where liquid erupts from ocean’s hidden in the moon’s interior.
For instance, Jupiter’s moon Europa, which is known to have an interior ocean, is believed to experiences cryovolcanism. The earliest evidence for this had to do with its smooth and young surface, which points towards endogenic resurfacing and renewal. Much like hot magma, water and volatiles erupt onto the surface where they then freeze to cover up impact craters and other features.
In addition, plumes of water were observed in 2012 and again in 2016 using the Hubble Space Telescope. These intermittent plumes were observed on both occasions to be coming in the southern region of Europa, and were estimated to be reach up to 200 km (125 miles) before depositing water ice and material back onto the surface.
In 2005, the Cassini-Huygens mission detected evidence of cryovolcanism on Saturn’s moons Titan and Enceladus. In the former case, the probe used infrared imaging to penetrate Titan’s dense clouds and detect signs of a 30 km (18.64 mi) formation, which was believed to be caused by the upwelling of hydrocarbon ices beneath the surface.
On Enceladus, cryovolcanic activity has been confirmed by observing plumes of water and organic molecules being ejected from the moon’s south pole. These plumes are are thought to have originated from the moon’s interior ocean, and are composed mostly of water vapor, molecular nitrogen, and volatiles (such as methane, carbon dioxide and other hydrocarbons).
In 1989, the Voyager 2 spacecraft observed cryovolcanoes ejecting plumes of water ammonia and nitrogen gas on Neptune’s moon Triton. These nitrogen geysers were observed sending plumes of liquid nitrogen 8 km (5 mi) above the surface of the moon. The surface is also quite young, which was seen as indication of endogenic resurfacing. It is also theorized that cryovolcanism may also be present on the Kuiper Belt Object Quaoar.
Here on Earth, volcanism takes the form of hot magma being pushed up through the Earth’s silicate crust due to convention in the interior. However, this kind of activity is present on all planet that formed from silicate material and minerals, and where geological activity or tidal stresses are known to exist. But on other bodies, it consists of cold water and materials from the interior ocean being forced through to the icy surface.
Color Mosaic of Olympus Mons on Mars. Credit: NASA/JPL
Today, our knowledge of volcanism (and the different forms it can take) is the result of improvements in both the field of geology, as well as space exploration. The more we learn of about other planets, the more we are able to see startling similarities and contrasts with our own (and vice versa).
