What is the gravity on Mars? NASA's Hubble Space Telescope took this close-up of the red planet Mars
The planet Mars has few things in common. Both planets have roughly the same amount of land surface area, sustained polar caps, and both have a similar tilt in their rotational axes, affording each of them strong seasonal variability. Additionally, both planets present strong evidence of having undergone climate change in the past. In Mars’ case, this evidence points towards it once having a viable atmosphere and liquid water on its surface.
At the same time, our two planets are really quite different, and in a number of very important ways. One of these is the fact that gravity on Mars is just a fraction of what it is here on Earth. Understanding the effect this will likely have on human beings is of extreme importance when it comes time to send crewed missions to Mars, not to mention potential colonists.
Mars Compared to Earth:
The differences between Mars and Earth are all crucial for the existence of life as we know it. For instance, atmospheric pressure on Mars is a tiny fraction of what it is here on Earth – averaging 7.5 millibars on Mars to just over 1000 here on Earth. The average surface temperature is also lower on Mars, ranking in at a frigid -63 °C compared to Earth’s balmy 14 °C.
Artist rendition of the interior of Mars. Image credit: NASA/JPL-Caltech
And while the length of a Martian day is roughly the same as it is here on Earth (24 hours 37 minutes), the length of a Martian year is significantly longer (687 days). On top that, the gravity on Mars’ surface is much lower than it is here on Earth – 62% lower to be precise. At just 0.376 of the Earth standard (or 0.376 g), a person who weighs 100 kg on Earth would weigh only 38 kg on Mars.
This difference in surface gravity is due to a number of factors – mass, density, and radius being the foremost. Even though Mars has almost the same land surface area as Earth, it has only half the diameter and less density than Earth – possessing roughly 15% of Earth’s volume and 11% of its mass.
Calculating Martian Gravity:
Scientists have calculated Mars’ gravity based on Newton’s Theory of Universal Gravitation, which states that the gravitational force exerted by an object is proportional to its mass. When applied to a spherical body like a planet with a given mass, the surface gravity will be approximately inversely proportional to the square of its radius. When applied to a spherical body with a given average density, it will be approximately proportional to its radius.
The Mars Gravity Model 2011 (MGM2011), showing variations of gravity accelerations over Mars’s surface. Credit: geodesy.curtin.edu.au
These proportionalities can be expressed by the formula g = m/r2, where g is the surface gravity of Mars (expressed as a multiple of the Earth’s, which is 9.8 m/s²), m is its mass – expressed as a multiple of the Earth’s mass (5.976·1024 kg) – and r its radius, expressed as a multiple of the Earth’s (mean) radius (6,371 km).
For instance, Mars has a mass of 6.4171 x 1023 kg, which is 0.107 times the mass of Earth. It also has a mean radius of 3,389.5 km, which works out to 0.532 Earth radii. The surface gravity of Mars can therefore be expressed mathematically as: 0.107/0.532², from which we get the value of 0.376. Based on the Earth’s own surface gravity, this works out to an acceleration of 3.711 meters per second squared.
Implications:
At present, it is unknown what effects long-term exposure to this amount of gravity will have on the human body. However, ongoing research into the effects of microgravity on astronauts has shown that it has a detrimental effect on health – which includes loss of muscle mass, bone density, organ function, and even eyesight.
Understanding Mars’ gravity and its affect on terrestrial beings is an important first step if we want to send astronauts, explorers, and even settlers there someday. Basically, the effects of long-term exposure to gravity that is just over one-third the Earth normal will be a key aspect of any plans for upcoming manned missions or colonization efforts.
Artist’s concept of a Martian astronaut standing outside the Mars One habitat. Credit: Bryan Versteeg/Mars One
For example, crowd-sourced projects like Mars One make allowances for the likelihood of muscle deterioration and osteoporosis for their participants. Citing a recent study of International Space Station (ISS) astronauts, they acknowledge that mission durations ranging from 4-6 months show a maximum loss of 30% muscle performance and maximum loss of 15% muscle mass.
Their proposed mission calls for many months in space to get to Mars, and for those volunteering to spend the rest of their lives living on the Martian surface. Naturally, they also claim that their astronauts will be “well prepared with a scientifically valid countermeasures program that will keep them healthy, not only for the mission to Mars, but also as they become adjusted to life under gravity on the Mars surface.” What these measures are remains to be seen.
Learning more about Martian gravity and how terrestrial organisms fare under it could be a boon for space exploration and missions to other planets as well. And as more information is produced by the many robotic lander and orbiter missions on Mars, as well as planned manned missions, we can expect to get a clearer picture of what Martian gravity is like up close.
As we get closer to NASA’s proposed manned mission to Mars, which is currently scheduled to take place in 2030, we can certainly expect that more research efforts will be attempted.
Research into the temporary slowdown of the global mean surface temperature has revealed that the world's oceans have absorbed the "missing heat." Image: Flickr user Brian Richardson, CC by 2.0
A reprieve from Global Warming? A hiatus? That would be nice, wouldn’t it? But in this case, a hiatus is not quite what it seems.
Everybody knows that global warming is partly caused by human activities, largely our use of fossil fuels. We understand how it works and we fear for the future. But there’s been a slowdown in the global mean surface temperature increase between 1998 to 2013. We haven’t lowered our emissions of greenhouse gases (GHGs) significantly during that time, so what happened?
Fossil fuels: we just can’t get enough of them. Image: a petrochemical refinery in Scotland. Credit: User:John from wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2459867
A new multi-institutional study involving NASA’s Jet Propulsion Laboratory (JPL), the National Oceanographic and Atmospheric Institute, and others, concludes that Earth’s oceans have absorbed the heat. So instead of the global mean surface temperature rising at a steady rate, the oceans have taken on the job as global heat sink. But what’s the significance of this?
“The hiatus period gives scientists an opportunity to understand uncertainties in how climate systems are measured, as well as to fill in the gap in what scientists know.” -Xiao-Hai Yan, University of Delaware, Newark
In terms of the on-going rise in the temperature of the globe, the hiatus is not that significant. But in terms of the science of global warming, and how well we understand it, the hiatus gives scientists an opportunity.
The new paper, titled “The Global Warming Hiatus: Slowdown or Redistribution?” grew out of the U.S. Climate Variability and Predictability Program (CLIVAR) panel session at the 2015 American Geophysical Union fall meeting. From those discussions, scientists reached consensus on three key points:
From 1998 to 2013, the rate of global mean surface warming slowed, which some call the “global warming hiatus.”
Natural variability plays a large role in the rate of global mean surface warming on decadal time scales.
Improved understanding of how the ocean distributes and redistributes heat will help the scientific community better monitor Earth’s energy budget. Earth’s energy budget is a complex calculation of how much energy enters our climate system from the sun and what happens to it: how much is stored by the land, ocean or atmosphere.
This graph shows the yearly global ocean heat content. The dashed line shows the 1958-65 average. Image: Balmaseda et al., 2013
The paper is a reminder that climate science is complex, and that the oceans play a big part in global warming. As Yan says, “To better monitor Earth’s energy budget and its consequences, the ocean is most important to consider because the amount of heat it can store is extremely large when compared to the land or atmospheric capacity.”
“…”arguably, ocean heat content — from the surface to the seafloor — might be a more appropriate measure of how much our planet is warming.” – from the paper “The Global Warming Hiatus: Slowdown or Redistribution?”
The team behind this new research suggests that saying there’s been a hiatus in global warming is confusing. They suggest “global warming hiatus” be replaced with “global surface warming slowdown.”
There’s a danger in calling it a “global warming hiatus.” Those opposed to climate change and who think it’s a hoax can use that term to discredit climate science. They’ll claim that the “hiatus” shows we don’t understand climate change and the Earth may have stopped warming. But in any case, it’s the long-term trend—change over the course of a century or more—that defines “global warming,” not the change from year to year or even decade to decade.
There’s much more to learn about the oceans’ role in global warming. Research shows that some ocean areas absorb heat much faster than others. But whatever the fine detail of it is, there is broad agreement in the scientific community that the global surface warming slowdown was caused by an increased uptake of heat energy by the world’s oceans.
A screenshot from the “NASA’s Eyes” app. The app allows anyone to check Earth’s vital signs. Image: NASA/JPL
NASA uses a lot of tools to monitor the Earth’s temperature. For an interesting look at the Earth’s vital signs, check out Nasa’s Eyes. This easy to use visualization tool lets you take a closer look at the Earth’s temperature, CO2 levels, soil moisture levels, sea levels, and other things.
Blastoff of revolutionary NASA/NOAA GOES-R (Geostationary Operational Environmental Satellite - R Series) on a ULA Atlas V from Space Launch Complex 41 (SLC-41) on Cape Canaveral Air Force Station, Florida on Nov. 19, 2016 - as seen from the VAB roof. GOES-R will soon deliver a quantum leap in America’s weather forecasting capabilities. Credit: Ken Kremer/kenkremer.com
Blastoff of revolutionary NASA/NOAA GOES-R (Geostationary Operational Environmental Satellite – R Series) on a ULA Atlas V from Space Launch Complex 41 (SLC-41) on Cape Canaveral Air Force Station, Florida on Nov. 19, 2016 – as seen from the VAB roof. GOES-R will soon deliver a quantum leap in America’s weather forecasting capabilities. Credit: Ken Kremer/kenkremer.com
Liftoff of the highly advanced Geostationary Operational Environmental Satellite-R (GOES-R) weather observatory bolted atop a ULA Atlas V rocket came at 6:42 p.m. EST on Saturday, Nov. 19, 2016 from Space Launch Complex 41 (SLC-41) on Cape Canaveral Air Force Station, Florida.
The launch was delayed for an hour until the very end of the launch window to deal with unexpected technical and Eastern range issues, that only added more drama and changed the sunset launch into a night launch for the hordes of spectators who gathered here from around the world – appropriate since this probe will touch the lives of humans world wide.
“It’s a dramatic leap in capability – like moving from black and white TV to HDTV,” explained Greg Mandt, the NOAA GOES-R program manager during a prelaunch media briefing in the cleanroom processing facility at Astrotech.
“This is a very exciting time,” explained Greg Mandt, the NOAA GOES-R program manager during the Astrotech cleanroom briefing.
“This is the culmination of about 15 years of intense work for the great team of NOAA and NASA and our contractors Lockheed Martin and Harris.”
“We are bringing the nation a new capability. The GOES program has been around for about 40 years and most every American sees it every night on the weather broadcasts when they see go to the satellite imagery. And what’s really exciting is that for the first time in that 40 years we are really end to end replacing the entire GOES system. The weather community is really excited about what we are bringing.”
GOES-R will bring about a “quantum leap” in weather forecasting capabilities that will soon lead to more accurate and timely forecasts, watches and warnings for the Earth’s Western Hemisphere when it becomes fully operational in about a year.
But the first images are expected within weeks! And both researchers and weather forecasters can’t wait to see, analyze and put to practical use the sophisticated new images and data that will improve forecasts and save lives during extreme weather events that are occurring with increasing frequency.
Blastoff of revolutionary NASA/NOAA GOES-R (Geostationary Operational Environmental Satellite – R Series) on ULA Atlas V from Space Launch Complex 41 (SLC-41) on Cape Canaveral Air Force Station, Florida on Nov. 19, 2016. GOES-R will deliver a quantum leap in America’s weather forecasting capabilities. Credit: Ken Kremer/kenkremer.com
GOES-R will be renamed GOES-16 after it reaches its final orbit 22,000 above Earth about two weeks from now.
Over the next year, teams of engineers and scientists will check out and validate the state of the art suite of six science instruments that also includes the first operational lightning mapper in geostationary orbit – dubbed the Geostationary Lightning Mapper (GLM).
“The launch of GOES-R represents a major step forward in terms of our ability to provide more timely and accurate information that is critical for life-saving weather forecasts and warnings,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington.
“It also continues a decades-long partnership between NASA and NOAA to successfully build and launch geostationary environmental satellites.”
GOES-R, which stands for Geostationary Operational Environmental Satellite – R Series – is a new and advanced transformational weather satellite that will vastly enhance the quality, speed and accuracy of weather forecasting available to forecasters for Earth’s Western Hemisphere.
The science suite includes the Advanced Baseline Imager (ABI), Geostationary Lightning Mapper (GLM), Solar Ultraviolet Imager (SUVI), Extreme Ultraviolet and X-Ray Irradiance Sensors (EXIS), Space Environment In-Situ Suite (SEISS), and the Magnetometer (MAG).
ABI is the primary instrument and will collect 3 times more spectral data with 4 times greater resolution and scans 5 times faster than ever before – via the primary Advanced Baseline Imager (ABI) instrument – compared to the current GOES satellites.
So instead of seeing weather as it was, viewers will see weather as it is.
Whereas the current GOES-NOP imagers scan the full hemispheric disk in 26 minutes, the new GOES-ABI can simultaneously scan the Western Hemisphere every 15 minutes, the Continental U.S. every 5 minutes and areas of severe weather every 30-60 seconds.
Launch of NASA/NOAA GOES-R weather observatory on ULA Atlas V on Nov. 19, 2016 from pad 41 on Cape Canaveral Air Force Station, Florida. Credit: Julian Leek
“The next generation of weather satellites is finally here,” said NOAA Administrator Kathryn Sullivan.
“GOES-R will strengthen NOAA’s ability to issue life-saving forecasts and warnings and make the United States an even stronger, more resilient weather-ready nation.”
Blastoff of revolutionary NASA/NOAA GOES-R (Geostationary Operational Environmental Satellite – R Series) on a ULA Atlas V from Space Launch Complex 41 (SLC-41) on Cape Canaveral Air Force Station, Florida on Nov. 19, 2016 – as seen from the VAB roof. GOES-R will soon deliver a quantum leap in America’s weather forecasting capabilities. Credit: Ken Kremer/kenkremer.com
It is designed to last for a 15 year orbital lifetime.
The 11,000 pound satellite was built by prime contractor Lockheed Martin and is the first of a quartet of four identical satellites – comprising GOES-R, S, T, and U – at an overall cost of about $11 Billion. This will keep the GOES satellite system operational through 2036.
Today’s launch was the 10th of the year for ULA and the 113th straight successful launch since the company was formed in December 2006.
GOES-R launched on the Atlas V 541 configuration vehicle, augmented by four solid rocket boosters on the first stage. The payload fairing is 5 meters (16.4 feet) in diameter. The first stage is powered by the RD AMROSS RD-180 engine. And the Centaur upper stage is powered by a single-engine Aerojet Rocketdyne RL10C engine.
This was only the fourth Atlas V launch employing the 541 configuration.
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
The NASA/NOAA GOES-R (Geostationary Operational Environmental Satellite – R Series) is poised for launch on a ULA Atlas V from Cape Canaveral, Florida on Nov. 19, 2016. GOES-R will be America’s most advanced weather satellite. Credit: Ken Kremer/kenkremer.comLaunch of NASA/NOAA GOES-R weather observatory on ULA Atlas V on Nov. 19, 2016 from pad 41 on Cape Canaveral Air Force Station, Florida, as seen from Playalinda beach. Credit: Jillian Laudick
………….
Learn more about GOES-R weather satellite, Heroes and Legends at KSCVC, OSIRIS-REx, InSight Mars lander, ULA, SpaceX and Orbital ATK missions, Juno at Jupiter, SpaceX AMOS-6 & CRS-9 rocket launch, ISS, ULA Atlas and Delta rockets, Orbital ATK Cygnus, Boeing, Space Taxis, Mars rovers, Orion, SLS, Antares, NASA missions and more at Ken’s upcoming outreach events:
Nov 19-20: “GOES-R weather satellite launch, OSIRIS-Rex, SpaceX and Orbital ATK missions to the ISS, Juno at Jupiter, ULA Delta 4 Heavy spy satellite, SLS, Orion, Commercial crew, Curiosity explores Mars, Pluto and more,” Kennedy Space Center Quality Inn, Titusville, FL, evenings
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.
Artists impression of a Super-Earth, a class of planet that has many times the mass of Earth, but less than a Uranus or Neptune-sized planet. Credit: NASA/Ames/JPL-Caltech
Red dwarf stars have proven to be a treasure trove for exoplanet hunters in recent years. In addition to multiple exoplanets candidates being detected around stars like TRAPPIST-1, Gliese 581, Gliese 667C, and Kepler 296, there was also the ESO’s recent discovery of a planet orbiting within the habitable zone of our Sun’s closest neighbor – Proxima Centauri.
And it seems the trend is likely to continue, with the latest discovery comes from a team of European scientists. Using data from the ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) and HARPS-N instruments, they detected an exoplanet candidate orbiting around GJ 536 – an M-class red dwarf star located about 32.7 light years (10.03 parsecs) from Earth.
According to their study, “A super-Earth Orbiting the Nearby M-dwarf GJ 536“, this planet is a super-Earth – a class of exoplanet that has between more than one, but less than 15, times the mass of Earth. In this case, the planet boasts a minimum of 5.36 ± 0.69 Earth masses, has an orbital period of 8.7076 ± 0.0025 days, and orbits its sun at a distance of 0.06661 AU.
Artist’s impression of a system of exoplanets orbiting a low mass, red dwarf star. Credit: NASA/JPL
The team was led by Dr. Alejandro Suárez Mascareño of the Instituto de Astrofísica de Canarias (IAC). The discovery of the planet was part of his thesis work, which was conducted under Dr Rafael Rebolo – who is also a member of the IAC, the Spanish National Research Council and a professor at the University of Laguna. And while the planet is not a potentially habitable world, it does present some interesting opportunities for exoplanet research.
As Dr. Mascareño shared with Universe Today via email:
“GJ 536 b is a small super Earth discovered in a very nearby star. It is part of the group of the smallest planets with measured mass. It is not in the habitable zone of its star, but its relatively close orbit and the brightness of its star makes it a promising target for transmission spectroscopy IF we can detect the transit. With a star so bright (V 9.7) it would be possible to obtain good quality spectra during the hypothetical transit to try to detect elements in the atmosphere of the planet. We are already designing a campaign for next year, but I guess we won’t be the only ones.”
The survey that found this planet was part of a joint effort between the IAC (Spain) and the Geneva Observatory (Switzerland). The data came from the HARPS and HARPS-N instruments, which are mounted on the ESO’s 3.6 meter telescope at the La Silla Observstory in Chile and the 3.6 meter telescope at the La Palma Observatory in Spain. This was combined with photometric data from the All Sky Automated Survey (ASAS), which has observatories in Chile and Maui.
The research team relied on radial velocity measurements from the star to discern the presence of the planet, as well as spectroscopic observations of the star that were taken over a 8.6 year period. For all this, they not only detected an exoplanet candidate with 5 times the mass of Earth, but also derived information on the star itself – which showed that it has a rotational period of about 44 days, and magnetic cycle that lasts less than three years.
Artist’s depiction of the interior of a low-mass star, such as the one seen in an X-ray image from Chandra in the inset. Credit: NASA/CXC/M.Weiss
By comparison, our Sun has a rotational period of 25 days and a magnetic cycle of 11 years, which is characterized by changes in the levels of solar radiation it emits, the ejection of solar material and in the appearance of sunspots. In addition, a recent study from the the Harvard Smithsonian Center for Astrophysics (CfA) showed that Proxima Centauri has a stellar magnetic cycle that lasts for 7 years.
This detection is just the latest in a long line of exoplanets being discovered around low-mass, low-luminosity, M-class (red dwarf) stars. And looking ahead, the team hopes to continue surveying GJ 536 to see if there is a planetary system, which could include some Earth-like planets, and maybe even a few gas giants.
“For now we have detected only one planet, but we plan to continue monitoring the star to search for other companions at larger orbital separations,” said Dr. Mascareño. “We estimate there is still room for other low-mass or even Neptune-mass planets at orbits from a hundred of days to a few years.”
The research also included scientists from the Astronomical Observatory at the University of Geneva, the University of Grenoble, The Astrophysical and Planetological Insitute of Grenoble, Institute of Astrophysics and Space Sciences in Portugal, and the University of Porto, Portugal.
An asteroid strike that could wreak some serious havoc against Earth may be statistically unlikely. But it's not like there's no precedent for one. Artist's Image: . Credit: NASA
Everyone knows it was a large asteroid striking Earth that led to the demise of the dinosaurs. But how many near misses were there? Modern humans have been around for about 225,000 years, so we must have come close to death by asteroid more than once in our time. We would have had no clue.
Of course, it’s the actual strikes that are cause for concern, not near misses. Efforts to predict asteroid strikes, and to catalogue asteroids that come close to Earth, have reached new levels. NASA’s newest tool in the fight against asteroids is called Scout. Scout is designed to detect asteroids approaching Earth, and it just passed an important test. Scout was able to give us 5 days notice of an approaching asteroid.
Here’s how Scout works. A telescope in Hawaii, the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) detected the asteroid, called 2016 UR36, and then alerted other ‘scopes. Three other telescopes confirmed 2016 UR36 and were able to narrow down its trajectory. They also learned its size, about 5 to 25 meters across.
The Pan STARRS telescope in Hawaii. Image: Institute for Astronomy, University of Hawaii.
After several hours, we knew that UR 36 would come close to us, but was not a threat to impact Earth. UR 36 would pass Earth at a distance of about 498,000 km. That’s about 1.3 times further away than the Moon.
The key part of this is that we had 5 days notice. And five days notice is a lot more than the few hours that we usually have. The approach of 2016 UR36 was the first test for the Scout system, and it passed the test.
Asteroids that come close to Earth are called Near Earth Objects (NEOs) and finding them and tracking them has become a growing concern for NASA. In fact NASA has about 15,000 NEOs catalogued, and they’re still finding about 5 more every night.
NASA is getting much better at discovering and detecting NEOs. Image: NASA/NEO Program.
Not only does NASA have the Scout system, whose primary role is to speed up the confirmation process for approaching asteroids, but they also have the Sentry program. Sentry’s role is a little different.
Sentry’s job is to focus on asteroids that are large enough to wipe out a city and cause widespread destruction. That means NEOs that are larger than about 140 metres. Sentry has over 600 large NEOs catalogued, and astronomers think there are a lot more of them out there.
NASA also has the Planetary Defense Coordination Office (PDCO), which has got to be the greatest name for an office ever. (Can you imagine having that on your business card?) Anyway, the PDCO has the over-arching role of preparing for asteroid impacts. The Office is there to make emergency plans to deal with the impact aftermath.
5 days notice for a small asteroid striking Earth is a huge step for preparedness. Resources can be mobilized, critical infrastructure can be protected, maybe things like atomic power plants can be shut down if necessary. And, of course, people can be evacuated.
We haven’t always had any notice for approaching asteroids. Look at the Chelyabinsk meteor from 2013. It was a 10,000 ton meteor that exploded over the Chelyabinsk Oblast, injuring 1500 people and damaging an estimated 3,000 building in 6 cities. If it had been a little bigger, and reached the surface of the Earth, the damage would have been widespread. 5 days notice would likely have saved a lot of lives.
Smaller asteroids may be too small to detect when they’re very far away. But larger ones can be detected when they’re still 10, 20, even 30 years away. That’s enough time to figure out how to stop them. And if you can reach them when they’re that far away, you only need to nudge them a little to deflect them away from Earth, and maybe to the Sun to be destroyed.
Large asteroids with the potential to cause widespread destruction are the attention-getters. Hollywood loves them. But it may be more likely that we face numerous impacts from smaller asteroids, and that they could cause more damage overall. Scout’s ability to detect these smaller asteroids, and give us several days notice of their approach, could be a life-saver.
The magnetic field and electric currents in and around Earth generate complex forces that have immeasurable impact on every day life. Credit: ESA/ATG medialab
Everyone knows just how fun magnets can be. As a child, who among us didn’t love to see if we could make our silverware stick together? And how about those little magnetic rocks that we could arrange to form just about any shape because they stuck together? Well, magnetism is not just an endless source of fun or good for scientific experiments; it’s also one of basic physical laws upon which the universe is based.
The attraction known as magnetism occurs when a magnetic field is present, which is a field of force produced by a magnetic object or particle. It can also be produced by a changing electric field and is detected by the force it exerts on other magnetic materials. Hence why the area of study dealing with magnets is known as electromagnetism.
Definition:
Magnetic fields can be defined in a number of ways, depending on the context. However, in general terms, it is an invisible field that exerts magnetic force on substances which are sensitive to magnetism. Magnets also exert forces and torques on each other through the magnetic fields they create.
Visualization of the solar wind encountering Earth’s magnetosphere. Like a dipole magnet, it has field lines and a northern and southern pole. Credit: JPL
They can be generated within the vicinity of a magnet, by an electric current, or a changing electrical field. They are dipolar in nature, which means that they have both a north and south magnetic pole. The Standard International (SI) unit used to measure magnetic fields is the Tesla, while smaller magnetic fields are measured in terms of Gauss (1 Tesla = 10,000 Guass).
Mathematically, a magnetic field is defined in terms of the amount of force it exerted on a moving charge. The measurement of this force is consistent with the Lorentz Force Law, which can be expressed as F= qvB, where F is the magnetic force, q is the charge, v is the velocity, and the magnetic field is B. This relationship is a vector product, where F is perpendicular (->) to all other values.
Field Lines:
Magnetic fields may be represented by continuous lines of force (or magnetic flux) that emerge from north-seeking magnetic poles and enter south-seeking poles. The density of the lines indicate the magnitude of the field, being more concentrated at the poles (where the field is strong) and fanning out and weakening the farther they get from the poles.
A uniform magnetic field is represented by equally-spaced, parallel straight lines. These lines are continuous, forming closed loops that run from north to south, and looping around again. The direction of the magnetic field at any point is parallel to the direction of nearby field lines, and the local density of field lines can be made proportional to its strength.
Magnetic field lines resemble a fluid flow, in that they are streamlined and continuous, and more (or fewer lines) appear depending on how closely a field is observed. Field lines are useful as a representation of magnetic fields, allowing for many laws of magnetism (and electromagnetism) to be simplified and expressed in mathematical terms.
A simple way to observe a magnetic field is to place iron filings around an iron magnet. The arrangements of these filings will then correspond to the field lines, forming streaks that connect at the poles. They also appear during polar auroras, in which visible streaks of light line up with the local direction of the Earth’s magnetic field.
History of Study:
The study of magnetic fields began in 1269 when French scholar Petrus Peregrinus de Maricourt mapped out the magnetic field of a spherical magnet using iron needles. The places where these lines crossed he named “poles” (in reference to Earth’s poles), which he would go on to claim that all magnets possessed.
During the 16th century, English physicist and natural philosopher William Gilbert of Colchester replicated Peregrinus’ experiment. In 1600, he published his findings in a treaties (De Magnete) in which he stated that the Earth is a magnet. His work was intrinsic to establishing magnetism as a science.
View of the eastern sky during the peak of this morning’s aurora. Credit: Bob King
In 1750, English clergyman and philosopher John Michell stated that magnetic poles attract and repel each other. The force with which they do this, he observed, is inversely proportional to the square of the distance, otherwise known as the inverse square law.
In 1785, French physicist Charles-Augustin de Coulomb experimentally verified Earths’ magnetic field. This was followed by 19th century French mathematician and geometer Simeon Denis Poisson created the first model of the magnetic field, which he presented in 1824.
By the 19th century, further revelations refined and challenged previously-held notions. For example, in 1819, Danish physicist and chemist Hans Christian Orsted discovered that an electric current creates a magnetic field around it. In 1825, André-Marie Ampère proposed a model of magnetism where this force was due to perpetually flowing loops of current, instead of the dipoles of magnetic charge.
In 1831, English scientist Michael Faraday showed that a changing magnetic field generates an encircling electric field. In effect, he discovered electromagnetic induction, which was characterized by Faraday’s law of induction (aka. Faraday’s Law).
A Faraday cage in power plant in Heimbach, Germany. Credit: Wikipedia Commons/Frank Vincentz
Between 1861 and 1865, Scottish scientist James Clerk Maxwell published his theories on electricity and magnetism – known as the Maxwell’s Equations. These equations not only pointed to the interrelationship between electricity and magnetism, but showed how light itself is an electromagnetic wave.
The field of electrodynamics was extended further during the late 19th and 20th centuries. For instance, Albert Einstein (who proposed the Law of Special Relativity in 1905), showed that electric and magnetic fields are part of the same phenomena viewed from different reference frames. The emergence of quantum mechanics also led to the development of quantum electrodynamics (QED).
Examples:
A classic example of a magnetic field is the field created by an iron magnet. As previously mentioned, the magnetic field can be illustrated by surrounding it with iron filings, which will be attracted to its field lines and form in a looping formation around the poles.
Larger examples of magnetic fields include the Earth’s magnetic field, which resembles the field produced by a simple bar magnet. This field is believed to be the result of movement in the Earth’s core, which is divided between a solid inner core and molten outer core which rotates in the opposite direction of Earth. This creates a dynamo effect, which is believed to power Earth’s magnetic field (aka. magnetosphere).
Computer simulation of the Earth’s field in a period of normal polarity between reversals.[1] The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. Credit: NASASuch a field is called a dipole field because it has two poles – north and south, located at either end of the magnet – where the strength of the field is at its maximum. At the midpoint between the poles the strength is half of its polar value, and extends tens of thousands of kilometers into space, forming the Earth’s magnetosphere.
Other celestial bodies have been shown to have magnetic fields of their own. This includes the gas and ice giants of the Solar System – Jupiter, Saturn, Uranus and Neptune. Jupiter’s magnetic field is 14 times as powerful as that of Earth, making it the strongest magnetic field of any planetary body. Jupiter’s moon Ganymede also has a magnetic field, and is the only moon in the Solar System known to have one.
Mars is believed to have once had a magnetic field similar to Earth’s, which was also the result of a dynamo effect in its interior. However, due to either a massive collision, or rapid cooling in its interior, Mars lost its magnetic field billions of years ago. It is because of this that Mars is believed to have lost most of its atmosphere, and the ability to maintain liquid water on its surface.
When it comes down to it, electromagnetism is a fundamental part of our Universe, right up there with nuclear forces and gravity. Understanding how it works, and where magnetic fields occur, is not only key to understanding how the Universe came to be, but may also help us to find life beyond Earth someday.
The "Global Tectonic and Volcanic Activity of the Last One Million Years" map. Credit: NASA/DTAM
For people who live on or near an active fault line – such as the San Andreas Fault in California, the Median Tectonic Line in Japan, or the Sunda Megathrust of southeast Asia – earthquakes are a regular part of life. Oftentimes, they can take the form of minor tremors that come and go without causing much damage.
But at other times, they are cataclysmic, causing widespread destruction and death tolls in the thousands or more. But what exactly is an earthquake? What geological forces lead to this destructive force? Where do they typically happen, and how many different types are there? And most importantly, how can we be better prepared for them?
Definition:
An earthquake is defined as a perceptible tremor in the surface of the Earth, which is caused by seismic waves resulting from the sudden release of energy in the Earth’s crust. Sometimes, they are detected because of the transfer of this energy to structures, causing noticeable shaking and noise. At other times, they can be violent enough to throw people and level entire cities.
Global earthquake epicenters, 1963–1998. Credit: NASA/DTAM
Generally, the term is used to describe any seismic event that generates seismic waves. An earthquake’s point of initial rupture is called its focus or hypocenter, while the point on the Earth directly above it (i.e. the most immediately-effected area) is called the epicenter.
Causes:
The structure of the Earth’s crust, which is divided into several “tectonic plates”, is responsible for most earthquakes. These plates are constantly in motion due to convection in the Earth’s semi-viscous upper mantle. Over time, these plates will separate and crash into each other, creating visible boundaries called faults.
When plates collide, they remain locked until enough pressure builds that one of them is forced under the other (a process known as subduction). This process occurs over the course of millions of years, and occasionally results in a serious release of energy, frictional heating and cracking along the fault lines (aka. an earthquake).
The energy waves that result are divided into two categories – surface waves and body waves. Surface waves are so-named because they are the energy that reaches the surface of the Earth, while body waves refer to the energy that remains within the planet’s interior.
Map of the Earth’s Tectonic Plates. Credit: msnucleus.org
It is estimated that only 10% or less of an earthquake’s total energy is radiated as seismic energy, while the rest is used to power the fracture growth or is converted into friction heat. However, what reaches the surface triggers all of the effects that we humans associate with earthquakes – i.e. tremors that vary in duration and intensity.
Occasionally, earthquakes can happen away from fault lines. These are due to some plate boundaries being located in regions of continental lithosphere, where deformation is spread out over a much larger area than the plate boundary. Under these conditions, earthquakes are related to strains developed within the broader zone of deformation.
Earthquakes within a plate (called “intraplate earthquakes”) can also happen as a result of internal stress fields, which are caused by interaction with neighboring plates, as well as sedimentary loading or unloading.
Aside from naturally occurring earthquakes (aka. tectonic earthquakes) that occur along tectonic plate lines (fault lines), there are also those that fall under the heading of “human-made earthquakes”. These are all the result of human activity, which is most often the result of nuclear testing.
Earthquakes can also be caused by human-made factors, such as nuclear testing. Credit: NNSA
This type of earthquake can been felt all from considerable distance after the detonation of a nuclear weapon. There is very little actual data that is readily available on this type of earthquake, but, compared to tectonic activity, it can be easily predicted and controlled.
Measurements:
Scientists measure earthquakes using seismometers, which measures sound waves through the Earth’s crust. There is also a method of measuring the intensity of an earthquake. It is known as the Richter Scale, which grades earthquakes from 1 to 10 based on their intensity.
Although there is no upper limit to the scale, most people set ten as the upper limit because no earthquakes equal to or greater than ten have been recorded. Scientist hypothesize that level 10 earthquakes were probably more common in prehistoric times, especially as the result of meteor impacts.
Effects of Earthquakes:
Earthquakes can happen on land or at sea, and can therefore trigger other natural disasters. In the case of those that take place on land, displacement of the ground is often the result, which can cause landslides or even volcanoes. When they take place at sea, the displacement of the seabed often results, causing a tsunami.
Map of earthquakes around the world in a seven day period. Credit: USGS / Google Maps / AJAX / SODA
Even though major earthquakes do not happen that often, they can cause substantial damage. In addition to the aforementioned natural disasters they can cause, earthquakes can also trigger fires when gas or electrical lines are damaged and floods when dams are destroyed.
Some of the most devastating earthquakes in history include the 1556 Shaanxi earthquake, which occurred on January 1556 in China. This quake resulted in widespread destruction of housing in the region – most of the housing being dwellings carved directly out of the silt stone mountain – and led to over 830,000 deaths.
The 1976 Tangshan earthquake, which took place in north-eastern China, was the deadliest of the 20th century, leading to he deaths of between 240,000 and 655,000 people. The 1960 Chilean earthquake is the largest earthquake that has been measured on a seismograph, reaching 9.5 magnitude on May 22nd, 1960.
And then there was the 2004 Indian Ocean earthquake, a seismic event that also triggered a massive tsunami that caused devastation throughout southeast Asia. This quake reached 9.1 – 9.3 on the Richter Scale, struck coastal communities with waves measuring up to 30 meters (100 ft) high, and caused the deaths of 230,000 people in 14 countries.
A village near the coast of Sumatra that was devastated by the 2004 Tsunami. Credit: Wikipedia Commons/US Navy
Warning Systems:
More than 3 million earthquakes occur each year, which works out to about 8,000 earthquakes each day. Most of these occur in specific regions, mainly because they usually happen along the borders of tectonic plates. Despite being difficult to predict (except where human agency is the cause) some early warning methods have been devised.
For instance, using seismological data obtained in well-understood fault regions, earthquakes can be reasonably predicted weeks or months in advance. Regional notifications are also used whenever earthquakes are in progress, but before the shocks have struck, allowing people time to seek shelter in time.
Much like volcanoes, tornadoes, and debris flows, earthquakes are a force of nature that is not to be taken lightly. While they are a regular feature of our planet’s geological activity, they have had a considerable impact on human societies. And just like the eruption that buried Pompeii or the Great Flood, they are remembered long after they strike!
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).
It’s been a while since I read the NASA manual on space helmet operation, but if I recall correctly, they really just have one major rule. When you go to space, keep your space helmet on.
I don’t care what haunting music those beguiling space sirens are playing. It doesn’t matter if you’ve got a serious case of space madness, and you’re hallucinating that you’re back on your Iowa farm, surrounded by your loved ones. Even if you just turned on an ancient terraforming machine and you’re stumbling around the surface of Mars like an idiot. You keep your helmet on.
Keep. Your. Helmet. On. Credit: NASA
Not convinced? Well then, allow me to explain what happens if you decide to break that rule. Without a helmet, and your own personal Earth-like atmosphere surrounding you, you’ll be exposed to the hard vacuum of space.
Within a moment, all the air will rush out of your lungs, and then you’ll fall unconscious in about 45 seconds. Starved for oxygen, you’ll die of suffocation in just a couple of minutes. Then you’ll freeze solid and float about forever. Just another meat asteroid in the Solar System.
That’s the official stance on space helmet operation, but just between you and me, there might be a little wiggle room. A few other places in the Solar System where you can take your helmet off for just a moment, and maybe not die instantaneously.
Earth is obviously safe. If you’re down here on the planet, and you’re still wearing your helmet, you’re missing the whole point of why you need a helmet in the first place. That space helmet rule only applies to space, silly, you can take it off down here.
In order to survive, the human body needs a few things. First, we need pressure surrounding our body, and helping to keep our lungs inflated. The Earth’s atmosphere provides that service, stacking a huge column of air down on top of you.
Without enough pressure, the air will blast out of your lungs and you’ll suffocate. Too much pressure and your lungs will crush and your heart will give out.
You’re going to want atmospheric pressure somewhere between .5 to 5 times the atmosphere of Earth.
If you can’t find air, then some other gas or even water will do in a pinch. You can’t breathe it, but it can provide the pressure you’re looking for.
Do not take your helmet off on the Moon. Credit: NASA
If you’ve got the pressure right, then your next priority will be the temperature. You know what it’s like to be too cold on Earth, and too hot, so use your judgement here. It’s too cold if you’re starting to die of hypothermia, and too hot if you’re above 60 C for a few minutes.
If you really want to thrive, find air you can breathe. Ideally a nice mixture of nitrogen and oxygen. Again, here on Earth, that column of air pushing down on you also allows you to breathe. If you swapped air for carbon dioxide or water, you’re going to need to hold your breath.
So what are some other places in the Solar System that you could take your helmet off for a few brief moments?
Your best bet is the planet Venus. Not down at the surface, where the temperature is hot enough to melt lead, and it’s 90 atmospheres pressure.
But up in the cloud tops, it’s a whole different story. At 52.5 kilometers altitude, the temperature is about 37 C. A little stifling, but not too bad. And the air pressure is about 65% Earth’s air pressure.
Hold your breath if you’re planning on taking off your helmet within the clouds of Venus. Credit: NASA
The problem is that this region is right in the middle of Venus’ sulphuric acid cloud layer, so you might inhale a mist of toxic acid if you tried to breathe. Not to mention the fact that Venus’ atmosphere is carbon dioxide, which means you’ll asphyxiate if you tried to breathe it.
But assuming you had some kind of air supply to breathe, and a suit to protect you from the sulphuric acid, you could hang around, without a helmet as long as you liked.
Take that! Overly draconian NASA helmet rules.
Out on the surface of Titan? Good news! The surface pressure on Titan is 1.45 times that of Earth. You won’t need a pressure helmet at all, ever. You will need a warming helmet, however, since the temperature on Titan is -179 C. You might be able to take that helmet off for a brief moment, before your face freezes, but don’t take a breath, otherwise you’ll freeze your lungs.
Want another location? No problem. Astronomers are pretty sure there are vast reservoirs of water under the surface of many moons and large objects in the Solar System, from Europa to Charon.
This artist’s concept of Jupiter’s moon Ganymede, the largest moon in the solar system, illustrates the club sandwich model of its interior oceans. You could try taking your helmet off while diving in them. Credit: NASA/JPL
They’re heated up through tidal interactions, and could be dozens of kilometers thick. Drill down through the ice sheet, and then just dive into the icy waters without a helmet. It’ll be really cold, and you won’t be able to breathe, but you can stay alive as long as you can hold your breath.
Did you jump out of your spacecraft and now you’re falling to your death into one of the Solar System’s gas giants? That’s bad news and it won’t end well. However, there’s a tiny silver lining. As you fall through the atmosphere of Jupiter, for example, there’ll be a moment when the temperature and pressure roughly match what your body can handle.
Go ahead and take your helmet off and enjoy that sweet spot before you plunge into the swirling hydrogen gas. Once again, though, don’t breathe. Hold your breath, the moment will last longer before you go unconscious.
And listen, if you really really need to take off your helmet in the cold vacuum of space, you can do it. Make sure you completely exhale so you don’t wreck your lungs. Then you’ve got about 45 seconds before you go unconscious.
That’s enough time to jump across to an open airlock, or kick that nasty xenomorph holding onto your leg into deep space.
Even though the NASA space helmet manual has one rule – keep your helmet on – you can see there are a few times and places where you can bend those rules without instantly dying. Use your judgement.
I’d like to thank Mechadense for posting a comment on an earlier Guide to Space YouTube video, which became the inspiration for this episode. Thanks for doing the math Mechadense and bringing the science.
![Computer simulation of the Earth's field in a period of normal polarity between reversals.[1] The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth's core](https://www.universetoday.com/wp-content/uploads/2010/03/Geodynamo_Between_Reversals-e1449100829326.gif)
