A high resolution stereo pair of Jupiter and its Great Red Spot, captured on February 26, 2015. The two images were taken roughly five minutes apart. Credit and copyright: Damian Peach.
Cross your eyes and take a look at this image. If you’re lucky, you will be treated to a wonderfully clear 3-D view of Jupiter and its Great Red Spot, without the aid of a stereoscope. Or — if you haven’t quite mastered the art of viewing stereo pairs — you might end up with eyestrain.
Prolific astrophotographer Damian Peach took these two shots roughly five minutes apart — which makes them a great candidate for creating a stereo pair.
“Inspired by a suggestion from Dr. Brian May,” Peach told Universe Today via email, “this is the first time I’ve had two excellent quality sets of data so close in time with the GRS right in the centre to attempt this. I completely reprocessed the data for both images to keep a soft natural appearance and to closely match the colour between them as possible.”
Peach also said he measured the size of the GRS at 15,500km in width.
Still trying to view this as a 3-D image? Try this suggestion from Oxford University:
Hold a finger a short distance in front of your eyes and stare at it. In the background you should see two copies of the stereo pair, giving four views altogether. Move your finger away from you until you see the middle two of the four images come together. You should now see just three images in the background. Try to direct your attention slowly toward the middle image without moving your eyes, and it should gradually come into focus.
See more of Peach’s great astrophotography at his website.
These six narrow-angle color images were made from the first ever "portrait" of the solar system taken by Voyager 1 on Valentine’s Day on Feb. 14, 1990, which was more than 4 billion miles from Earth and about 32 degrees above the ecliptic. Venus, Earth, Jupiter, and Saturn, Uranus, Neptune are seen in these blown-up images, from left to right and top to bottom. Credit: NASA/JPL-Caltech
A quarter of a century has passed since NASA’s Voyager 1 spacecraft snapped the iconic image of Earth known as the “Pale Blue Dot” that shows all of humanity as merely a tiny point of light.
The outward bound Voyager 1 space probe took the ‘pale blue dot’ image of Earth 25 years ago on Valentine’s Day, on Feb. 14, 1990 when it looked back from its unique perch beyond the orbit of Neptune to capture the first ever “portrait” of the solar system from its outer realms.
Voyager 1 was 4 billion miles from Earth, 40 astronomical units (AU) from the sun and about 32 degrees above the ecliptic at that moment.
The idea for the images came from the world famous astronomer Carl Sagan, who was a member of the Voyager imaging team at the time.
He head the idea of pointing the spacecraft back toward its home for a last look as a way to inspire humanity. And to do so before the imaging system was shut down permanently thereafter to repurpose the computer controlling it, save on energy consumption and extend the probes lifetime, because it was so far away from any celestial objects.
Sagan later published a well known and regarded book in 1994 titled “Pale Blue Dot,” that refers to the image of Earth in Voyagers series.
This narrow-angle color image of the Earth, dubbed “Pale Blue Dot,” is a part of the first ever “portrait” of the solar system taken by Voyager 1 on Valentine’s Day on Feb. 14, 1990. Credit: NASA/JPL-Caltech
“Twenty-five years ago, Voyager 1 looked back toward Earth and saw a ‘pale blue dot,’ ” an image that continues to inspire wonderment about the spot we call home,” said Ed Stone, project scientist for the Voyager mission, based at the California Institute of Technology, Pasadena, in a statement.
Six of the Solar System’s nine known planets at the time were imaged, including Venus, Earth, Jupiter, and Saturn, Uranus, Neptune. The other three didn’t make it in. Mercury was too close to the sun, Mars had too little sunlight and little Pluto was too dim.
Voyager snapped a series of images with its wide angle and narrow angle cameras. Altogether 60 images from the wide angle camera were compiled into the first “solar system mosaic.”
Voyager 1 was launched in 1977 from Cape Canaveral Air Force Station in Florida as part of a twin probe series with Voyager 2. They successfully conducted up close flyby observations of the gas giant outer planets including Jupiter, Saturn, Uranus and Neptune in the 1970s and 1980s.
Both probes still operate today as part of the Voyager Interstellar Mission.
“After taking these images in 1990, we began our interstellar mission. We had no idea how long the spacecraft would last,” Stone said.
Hurtling along at a distance of 130 astronomical units from the sun, Voyager 1 is the farthest human-made object from Earth.
Solar System Portrait – 60 Frame Mosaic. The cameras of Voyager 1 on Feb. 14, 1990, pointed back toward the sun and took a series of pictures of the sun and the planets, making the first ever “portrait” of our solar system as seen from the outside. Missing are Mercury, Mars and Pluto. Credit: NASA/JPL-Caltech
Voyager 1 still operates today as the first human made instrument to reach interstellar space and continues to forge new frontiers outwards to the unexplored cosmos where no human or robotic emissary as gone before.
Here’s what Sagan wrote in his “Pale Blue Dot” book:
“That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. … There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
A montage of planets and other objects in the solar system. Credit: NASA/JPL
While the universe is a big place to study, we shouldn’t forget our own backyard. With eight planets and a wealth of smaller worlds to look at, there’s more than enough to learn for a few lifetimes!
So what are some of the most surprising things about the planets? We’ve highlighted a few things below.
1. Mercury is hot, but not too hot for ice
The closest planet to the Sun does indeed have ice on its surface. That sounds surprising at first glance, but the ice is found in permanently shadowed craters — those that never receive any sunlight. It is thought that perhaps comets delivered this ice to Mercury in the first place. In fact, NASA’s MESSENGER spacecraft not only found ice at the north pole, but it also found organics, which are the building blocks for life. Mercury is way too hot and airless for life as we know it, but it shows how these elements are distributed across the Solar System.
2. Venus doesn’t have any moons, and we aren’t sure why.
Both Mercury and Venus have no moons, which can be considered a surprise given there are dozens of other ones around the Solar System. Saturn has over 60, for example. And some moons are little more than captured asteroids, which may have been what happened with Mars’ two moons, for example. So what makes these planets different? No one is really sure why Venus doesn’t, but there is at least one stream of research that suggests it could have had one in the past.
Mars, as it appears today, Credit: NASA
3. Mars had a thicker atmosphere in the past.
What a bunch of contrasts in the inner Solar System: practically atmosphere-less Mercury, a runaway hothouse greenhouse effect happening in Venus’ thick atmosphere, temperate conditions on much of Earth and then a thin atmosphere on Mars. But look at the planet and you can see gullies carved in the past from probable water. Water requires more atmosphere, so Mars had more in the past. Where did it go? Some scientists believe it’s because the Sun’s energy pushed the lighter molecules out of Mars’ atmosphere over millions of years, decreasing the thickness over time.
4. Jupiter is a great comet catcher.
The most massive planet in the Solar System probably had a huge influence on its history. At 318 times the mass of Earth, you can imagine that any passing asteroid or comet going near Jupiter has a big chance of being caught or diverted. Maybe Jupiter was partly to blame for the great bombardment of small bodies that peppered our young Solar System early in its history, causing scars you can still see on the Moon today. And in 1994, astronomers worldwide were treated to a rare sight: a comet, Shoemaker-Levy 9, breaking up under Jupiter’s gravity and slamming into the atmosphere.
Fragmentation of comets is common. Many sungrazers are broken up by thermal and tidal stresses during their perihelions. At top, an image of the comet Shoemaker-Levy 9 (May 1994) after a close approach with Jupiter which tore the comet into numerous fragments. An image taken by Andrew Catsaitis of components B and C of Comet 73P/Schwassmann–Wachmann 3 as seen together on 31 May 2006 (Credit: NASA/HST, Wikipedia, A.Catsaitis)
5. No one knows how old Saturn’s rings are
There’s a field of ice and rock debris circling Saturn that from afar, appear as rings. Early telescope observations of the planet in the 1600s caused some confusion: does that planet have ears, or moons, or what? With better resolution, however, it soon became clear that there was a chain of small bodies encircling the gas giant. It’s possible that a single moon tore apart under Saturn’s strong gravity and produced the rings. Or, maybe they’ve been around (pun intended) for the last few billion years, unable to coalesce into a larger body but resistant enough to gravity not to break up.
6. Uranus is more stormy than we thought.
When Voyager 2 flew by the planet in the 1980s, scientists saw a mostly featureless blue ball and some assumed there wasn’t much activity going on on Uranus. We’ve had a better look at the data since then that does show some interesting movement in the southern hemisphere. Additionally, the planet drew closer to the Sun in 2007, and in more recent years telescope probing has shown some storms going on. What is causing all this activity is difficult to say unless we were to send another probe that way. And unfortunately, there are no missions yet that are slated for sure to zoom out to that part of the Solar System.
Infrared images of Uranus showing storms at 1.6 and 2.2 microns obtained Aug. 6, 2014 by the 10-meter Keck telescope. Credit: Imke de Pater (UC Berkeley) & Keck Observatory images.
7. Neptune has supersonic winds.
While on Earth we are concerned about hurricanes, the strength of these storms is nowhere near what you would find on Neptune. At its highest altitudes, according to NASA, winds blow at more than 1,100 miles per hour (1,770 kilometers per hour). To put that in context, that’s faster than the speed of sound on Earth, at sea level. Why Neptune is so blustery is a mystery, especially considering the Sun’s heat is so little at its distance.
8. You can see Earth’s magnetic field at work during light shows.
We have a magnetic field surrounding our planet that protects us from the blasts of radiation and particles the Sun sends our way. Good thing, too, because such flare-ups could prove deadly to unprotected people; that’s why NASA keeps an eye on solar activity for astronauts on the International Space Station, for example. At any rate, when you see auroras shining in the sky, that’s what happens when the particles from the Sun flow along the magnetic field lines and interact with Earth’s upper atmosphere.
Universe Today has many articles on interesting facts about the planets. Start with 10 facts about Mercury and 10 facts about Venus. You may also want to check out the 10 facts about Mars. Astronomy Cast also has a number of podcasts about the planets, including one on Earth.
This colorized image taken by the Cassini orbiter, shows Saturn's A and F rings, the small moon Epimetheus and Titan, the planet's largest moon.
Credit: NASA/JPL/Space Science Institute
Planetary rings are an interesting phenomena. The mere mention of these two words tends to conjure up images of Saturn, with its large and colorful system of rings that form an orbiting disk. But in fact, several other planets in our Solar System have rings. It’s just that, unlike Saturn, their systems are less visible, and perhaps less beautiful to behold.
Thanks to exploration efforts mounted in the past few decades, which have seen space probes dispatched to the outer Solar System, we have come to understand that all the gas giants – Jupiter, Saturn, Uranus and Neptune – all have their own ring systems. And that’s not all! In fact, ring systems may be more common than previously thought…
Jupiter’s Rings:
In was not until 1979 that the rings of Jupiter were discovered when the Voyager 1 space probe conducted a flyby of the planet. They were also thoroughly investigated in the 1990s by the Galileo orbiter. Because it is composed mainly of dust, the ring system is faint and can only be observed by the most powerful telescopes, or up-close by orbital spacecraft. However, during the past twenty-three years, it has been observed from Earth numerous times, as well as by the Hubble Space Telescope.
A schema of Jupiter’s ring system showing the four main components. Credit: NASA/JPL/Cornell University
The ring system has four main components: a thick inner torus of particles known as the “halo ring”; a relatively bright, but extremely thin “main ring”; and two wide, thick, and faint outer “gossamer rings”. These outer rings are composed of material from the moons Amalthea and Thebe and are named after these moons (i.e. the “Amalthea Ring” and “Thebe Ring”).
The main and halo rings consist of dust ejected from the moons Metis, Adrastea, and other unobserved parent bodies as the result of high-velocity impacts. Scientists believe that a ring could even exist around the moon of Himalia’s orbit, which could have been created when another small moon crashed into it and caused material to be ejected from the surface.
Saturn’s Rings:
The rings of Saturn, meanwhile, have been known for centuries. Although Galileo Galilei became the first person to observe the rings of Saturn in 1610, he did not have a powerful enough telescope to discern their true nature. It was not until 1655 that Christiaan Huygens, the Dutch mathematician and scientist, became the first person to describe them as a disk surrounding the planet.
Subsequent observations, which included spectroscopic studies by the late 19th century, confirmed that they are composed of smaller rings, each one made up of tiny particles orbiting Saturn. These particles range in size from micrometers to meters that form clumps orbiting the planet, and which are composed almost entirely of water ice contaminated with dust and chemicals.
Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute/Gordan Ugarkovic
In total, Saturn has a system of 12 rings with 2 divisions. It has the most extensive ring system of any planet in our solar system. The rings have numerous gaps where particle density drops sharply. In some cases, this due to Saturn’s Moons being embedded within them, which causes destabilizing orbital resonances to occur.
However, within the Titan Ringlet and the G Ring, orbital resonance with Saturn’s moons has a stabilizing influence. Well beyond the main rings is the Phoebe ring, which is tilted at an angle of 27 degrees to the other rings and, like Phoebe, orbits in retrograde fashion.
Uranus’ Rings:
The rings of Uranus are thought to be relatively young, at not more than 600 million years old. They are believed to have originated from the collisional fragmentation of a number of moons that once existed around the planet. After colliding, the moons probably broke up into numerous particles, which survived as narrow and optically dense rings only in strictly confined zones of maximum stability.
Uranus has 13 rings that have been observed so far. They are all very faint, the majority being opaque and only a few kilometers wide. The ring system consists mostly of large bodies 0.2 to 20 m in diameter. A few rings are optically thin and are made of small dust particles which makes them difficult to observe using Earth-based telescopes.
The labeled ring arcs of Neptune as seen in newly processed data. Credit: M. Showalter/SETI Institute
Neptune’s Rings:
The rings of Neptune were not discovered until 1989 until the Voyager 2 space probe conducted a flyby of the planet. Six rings have been observed in the system, which are best described as faint and tenuous. The rings are very dark, and are likely composed by organic compounds processed by radiation, similar to that found in the rings of Uranus. Much like Uranus, and Saturn, four of Neptune’s moons orbit within the ring system.
Other Bodies:
Back in 2008, it was suggested that the magnetic effects around the Saturnian moon of Rhea may indicate that it has its own ring system. However, a subsequent study indicated that observations obtained the Cassini mission suggested that some other mechanism was responsible for the magnetic effects.
Years before the the New Horizons probe visited the system, astronomers speculated that Pluto might also have a ring system. However, after conducting its historic flyby of the system in July of 2015, the New Horizons probe did not find any evidence of a ring system. While the dwarf planet had many satellites aside from its largest (Charon), debris from around the planet has not coalesced into rings, as was theorized.
Artist’s impression of the New Horizons spacecraft in orbit around Pluto (Charon is seen in the background). Credit: NASA/JPL
The minor planet of Chariklo – an asteroid that orbits the Sun between Saturn and Uranus – also has two rings that orbit it. These are perhaps due to a collision that caused a chain of debris to form in orbit around it. The announcement of these rings was made on March 26th of 2014, and was based on observations made during a stellar occultation on June 3rd, 2013.
This was followed by findings made in 2015 that indicated that 2006 Chiron – another major Centaur – could have a ring of its own. This led to further speculation that there might be many minor planets in our Solar System that have a system of rings.
In short, four planets in our Solar System have intricate ring systems, as well as the minor planet Chariklo, and perhaps even many other smaller objects. In this sense, ring systems appear to be a lot more common in our Solar System than previously thought.
A halo rings the bright moon and planet Jupiter (left of moon) Credit: Bob King
The Full Moon celebrates Jupiter’s coming opposition by accompanying the bright planet in a beautiful conjunction tonight.
Even last night Jupiter and the Moon were close enough to attract attention. Tonight they’ll be even more striking. Two reasons for that. The Moon is full this evening and will have crept within 41/2° of the planet. They’ll rise together and roll together all night long.
The Full Snow Moon will share the sky with Jupiter in Cancer tonight not far from the Sickle or head of Leo the Lion. The map shows the scene around 8 o’clock local time. Source: Stellarium
February’s full moon is aptly named the Full Snow Moon as snowfall can be heavy this month. Just ask the folks in Chicago. The Cherokee Indians called it the “Bone Moon”, named for the tough times experienced by many Native Americans in mid-winter when food supplies ran low. With little left to eat people made use of everything including bones and bone marrow for soup.
Not only is the Full Moon directly opposite the Sun in the sky, rising around sunset and setting around sunrise, but in mid-winter they’re nearly on opposite ends of the celestial seesaw.
Jupiter, like tonight’s Full Moon, will be directly opposite the Sun this Friday and in “full moon” phase. Because both planets are lined up on the same side of the Sun, Jupiter will also be at its closest to us for the year. Credit: Bob King
In early February the Sun is still near its lowest point in the sky (bottom of the seesaw) for the northern half of the globe. And while daylight is steadily increasing as the Sun moves northward, darkness still has the upper hand this month. Full Moons like tonight’s lie 180° opposite the Sun, placing the Moon near the top of the seesaw. Come early August, the Sun will occupy the Moon’s spot and the Full Moon will have slid down to the Sun’s current position. Yin and Yang folks.
Now here’s the interesting thing. Jupiter will also be in “full moon” phase when it reaches opposition this Friday Feb. 6. Take a look at the diagram. From our perspective on Earth, Jupiter and the Sun lie on opposite sides of our planet 180° apart. As the Sun sets Friday, Jupiter will rise in the east and remain visible all night until setting around sunrise exactly like a Full Moon.
So in a funny way, we have two Full Moons this week only one’s a planet.
Like me, a lot of you enjoy a good moonrise. That golden-orange globe, the crazy squished appearance at rising and the transition to the bright, white, beaming disk that throws enough light on a winter night to ski in the forest without a headlamp. All good reasons to be alive.
If Jupiter were moved to the Moon’s distance it would span about 20 degrees or 40 times the apparent diameter of the Full Moon. Credit: Roscosmos with additions by the author
To find when the moon rises for your town, click over to this moonrise calculator. As you step outside tonight to get your required Moon and Jupiter-shine, consider the scene if we took neighboring Jupiter and placed it at the same distance as the Moon. A recent series of such scenes was released by the Russian Federal Space Agency (Roscosmos). I included one here and added the Moon for you to compare. Is Jupiter enormous or what?
The Eight Planets of our Solar System. Credit: IAU
Our Solar System is a pretty picturesque place. Between the Sun, the Moon, and the Inner and Outer Solar System, there is no shortage of wondrous things to behold. But arguably, it is the eight planets that make up our Solar System that are the most interesting and photogenic. With their spherical discs, surface patterns and curious geological formations, Earth’s neighbors have been a subject of immense fascination for astronomers and scientists for millennia.
And in the age of modern astronomy, which goes beyond terrestrial telescopes to space telescopes, orbiters and satellites, there is no shortage of pictures of the planets. But here are a few of the better ones, taken with high-resolutions cameras on board spacecraft that managed to capture their intricate, picturesque, and rugged beauty.
Mercury, as imaged by the MESSENGER spacecraft, revealing parts never before seen by human eyes. Image Credit: NASA/Johns Hopkins University/Carnegie Institution of Washington
Named after the winged messenger of the gods, Mercury is the closest planet to our Sun. It’s also the smallest (now that Pluto is no longer considered a planet. At 4,879 km, it is actually smaller than the Jovian moon of Ganymede and Saturn’s largest moon, Titan.
Because of its slow rotation and tenuous atmosphere, the planet experiences extreme variations in temperature – ranging from -184 °C on the dark side and 465 °C on the side facing the Sun. Because of this, its surface is barren and sun-scorched, as seen in the image above provided by the MESSENGER spacecraft.
A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL
Venus is the second planet from our Sun, and Earth’s closest neighboring planet. It also has the dubious honor of being the hottest planet in the Solar System. While farther away from the Sun than Mercury, it has a thick atmosphere made up primarily of carbon dioxide, sulfur dioxide and nitrogen gas. This causes the Sun’s heat to become trapped, pushing average temperatures up to as high as 460°C. Due to the presence of sulfuric and carbonic compounds in the atmosphere, the planet’s atmosphere also produces rainstorms of sulfuric acid.
Because of its thick atmosphere, scientists were unable to examine of the surface of the planet until 1970s and the development of radar imaging. Since that time, numerous ground-based and orbital imaging surveys have produced information on the surface, particularly by the Magellan spacecraft (1990-94). The pictures sent back by Magellan revealed a harsh landscape dominated by lava flows and volcanoes, further adding to Venus’ inhospitable reputation.
Earth viewed from the Moon by the Apollo 11 spacecraft. Credit: NASA
Earth is the third planet from the Sun, the densest planet in our Solar System, and the fifth largest planet. Not only is 70% of the Earth’s surface covered with water, but the planet is also in the perfect spot – in the center of the hypothetical habitable zone – to support life. It’s atmosphere is primarily composed of nitrogen and oxygen and its average surface temperatures is 7.2°C. Hence why we call it home.
Being that it is our home, observing the planet as a whole was impossible prior to the space age. However, images taken by numerous satellites and spacecraft – such as the Apollo 11 mission, shown above – have been some of the most breathtaking and iconic in history.
The first true-colour image of Mars taken by the ESA’s Rosetta spacecraft on 24 February 2007. Credit: MPS for OSIRIS Team MPS/UPD/LAM/ IAA/ RSSD/ INTA/ UPM/ DASP/ IDA
Mars is the fourth planet from our Sun and Earth’s second closest neighbor. Roughly half the size of Earth, Mars is much colder than Earth, but experiences quite a bit of variability, with temperatures ranging from 20 °C at the equator during midday, to as low as -153 °C at the poles. This is due in part to Mars’ distance from the Sun, but also to its thin atmosphere which is not able to retain heat.
Mars is famous for its red color and the speculation it has sparked about life on other planets. This red color is caused by iron oxide – rust – which is plentiful on the planet’s surface. It’s surface features, which include long “canals”, have fueled speculation that the planet was home to a civilization.
Observations made by satellites flybys in the 1960’s (by the Mariner 3 and 4 spacecraft) dispelled this notion, but scientists still believe that warm, flowing water once existed on the surface, as well as organic molecules. Since that time, a small army of spacecraft and rovers have taken the Martian surface, and have produced some of the most detailed and beautiful photos of the planet to date.
Jupiter’s Great Red Spot and Ganymede’s Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)
Jupiter, the closest gas giant to our Sun, is also the largest planet in the Solar System. Measuring over 70,000 km in radius, it is 317 times more massive than Earth and 2.5 times more massive than all the other planets in our Solar System combined. It also has the most moons of any planet in the Solar System, with 67 confirmed satellites as of 2012.
Despite its size, Jupiter is not very dense. The planet is comprised almost entirely of gas, with what astronomers believe is a core of metallic hydrogen. Yet, the sheer amount of pressure, radiation, gravitational pull and storm activity of this planet make it the undisputed titan of our Solar System.
Jupiter has been imaged by ground-based telescopes, space telescopes, and orbiter spacecraft. The best ground-based picture was taken in 2008 by the ESO’s Very Large Telescope (VTL) using its Multi-Conjugate Adaptive Optics Demonstrator (MAD) instrument. However, the greatest images captured of the Jovian giant were taken during flybys, in this case by the Galileo and Cassini missions.
Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute/Gordan Ugarkovic
Saturn, the second gas giant closest to our Sun, is best known for its ring system – which is composed of rocks, dust, and other materials. All gas giants have their own system of rings, but Saturn’s system is the most visible and photogenic. The planet is also the second largest in our Solar System, and is second only to Jupiter in terms of moons (62 confirmed).
Much like Jupiter, numerous pictures have been taken of the planet by a combination of ground-based telescopes, space telescopes and orbital spacecraft. These include the Pioneer, Voyager, and most recently, Cassini spacecraft.
Uranus, seen by Voyager 2 spacecraft. Image credit: NASA/JPL
Another gas giant, Uranus is the seventh planet from our Sun and the third largest planet in our Solar System. The planet contains roughly 14.5 times the mass of the Earth, but it has a low density. Scientists believe it is composed of a rocky core that is surrounded by an icy mantle made up of water, ammonia and methane ice, which is itself surrounded by an outer gaseous atmosphere of hydrogen and helium.
It is for this reason that Uranus is often referred to as an “ice planet”. The concentrations of methane are also what gives Uranus its blue color. Though telescopes have captured images of the planet, only one spacecraft has even taken pictures of Uranus over the years. This was the Voyager 2 craft which performed a flyby of the planet in 1986.
Neptune from Voyager 2. Image credit: NASA/JPL
Neptune is the eight planet of our Solar System, and the farthest from the Sun. Like Uranus, it is both a gas giant and ice giant, composed of a solid core surrounded by methane and ammonia ices, surrounded by large amounts of methane gas. Once again, this methane is what gives the planet its blue color. It is also the smallest gas giant in the outer Solar System, and the fourth largest planet.
All of the gas giants have intense storms, but Neptune has the fastest winds of any planet in our Solar System. The winds on Neptune can reach up to 2,100 kilometers per hour, and the strongest of which are believed to be the Great Dark Spot, which was seen in 1989, or the Small Dark Spot (also seen in 1989). In both cases, these storms and the planet itself were observed by the Voyager 2 spacecraft, the only one to capture images of the planet.
Artist's impression of the planets in our solar system, along with the Sun (at bottom). Credit: NASA
It’s is no secret that Earth is the only inhabited planet in our Solar System. All the planets besides Earth lack a breathable atmosphere for terrestrial beings, but also, many of them are too hot or too cold to sustain life. A “habitable zone” which exists within every system of planets orbiting a star. Those planets that are too close to their sun are molten and toxic, while those that are too far outside it are icy and frozen.
But at the same time, forces other than position relative to our Sun can affect surface temperatures. For example, some planets are tidally locked, which means that they have one of their sides constantly facing towards the Sun. Others are warmed by internal geological forces and achieve some warmth that does not depend on exposure to the Sun’s rays. So just how hot and cold are the worlds in our Solar System? What exactly are the surface temperatures on these rocky worlds and gas giants that make them inhospitable to life as we know it?
Mercury:
Of our eight planets, Mercury is closest to the Sun. As such, one would expect it to experience the hottest temperatures in our Solar System. However, since Mercury also has no atmosphere and it also spins very slowly compared to the other planets, the surface temperature varies quite widely.
What this means is that the side exposed to the Sun remains exposed for some time, allowing surface temperatures to reach up to a molten 465 °C. Meanwhile, on the dark side, temperatures can drop off to a frigid -184°C. Hence, Mercury varies between extreme heat and extreme cold and is not the hottest planet in our Solar System.
Venus is an incredibly hot and hostile world, due to a combination of its thick atmosphere and proximity to the Sun. Image Credit: NASA/JPL
Venus:
That honor goes to Venus, the second closest planet to the Sun which also has the highest average surface temperatures – reaching up to 460 °C on a regular basis. This is due in part to Venus’ proximity to the Sun, being just on the inner edge of the habitability zone, but also to Venus’ thick atmosphere, which is composed of heavy clouds of carbon dioxide and sulfur dioxide.
These gases create a strong greenhouse effect which traps a significant portion of the Sun’s heat in the atmosphere and turns the planet surface into a barren, molten landscape. The surface is also marked by extensive volcanoes and lava flows, and rained on by clouds of sulfuric acid. Not a hospitable place by any measure!
Earth:
Earth is the third planet from the Sun, and so far is the only planet that we know of that is capable of supporting life. The average surface temperature here is about 14 °C, but it varies due to a number of factors. For one, our world’s axis is tilted, which means that one hemisphere is slanted towards the Sun during certain times of the year while the other is slanted away.
This not only causes seasonal changes, but ensures that places located closer to the equator are hotter, while those located at the poles are colder. It’s little wonder then why the hottest temperature ever recorded on Earth was in the deserts of Iran (70.7 °C) while the lowest was recorded in Antarctica (-89.2 °C).
Mars’ thin atmosphere, visible on the horizon, is too weak to retain heat. Credit: NASA
Mars:
Mars’ average surface temperature is -55 °C, but the Red Planet also experiences some variability, with temperatures ranging as high as 20 °C at the equator during midday, to as low as -153 °C at the poles. On average though, it is much colder than Earth, being just on the outer edge of the habitable zone, and because of its thin atmosphere – which is not sufficient to retain heat.
In addition, its surface temperature can vary by as much as 20 °C due to Mars’ eccentric orbit around the Sun (meaning that it is closer to the Sun at certain points in its orbit than at others).
Jupiter:
Since Jupiter is a gas giant, it has no solid surface, so it has no surface temperature. But measurements taken from the top of Jupiter’s clouds indicate a temperature of approximately -145°C. Closer to the center, the planet’s temperature increases due to atmospheric pressure.
At the point where atmospheric pressure is ten times what it is on Earth, the temperature reaches 21°C, what we Earthlings consider a comfortable “room temperature”. At the core of the planet, the temperature is much higher, reaching as much as 35,700°C – hotter than even the surface of the Sun.
Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute/Gordan Ugarkovic
Saturn:
Due to its distance from the Sun, Saturn is a rather cold gas giant planet, with an average temperature of -178 °Celsius. But because of Saturn’s tilt, the southern and northern hemispheres are heated differently, causing seasonal temperature variation.
And much like Jupiter, the temperature in the upper atmosphere of Saturn is cold, but increases closer to the center of the planet. At the core of the planet, temperatures are believed to reach as high as 11,700 °C.
Uranus:
Uranus is the coldest planet in our Solar System, with a lowest recorded temperature of -224°C. Despite its distance from the Sun, the largest contributing factor to its frigid nature has to do with its core.
Much like the other gas giants in our Solar System, the core of Uranus gives off far more heat than is absorbed from the Sun. However, with a core temperature of approximately 4,737 °C, Uranus’ interior gives of only one-fifth the heat that Jupiter’s does and less than half that of Saturn.
Neptune photographed by Voyager 2. Image credit: NASA/JPL
Neptune:
With temperatures dropping to -218°C in Neptune’s upper atmosphere, the planet is one of the coldest in our Solar System. And like all of the gas giants, Neptune has a much hotter core, which is around 7,000°C.
In short, the Solar System runs the gambit from extreme cold to extreme hot, with plenty of variance and only a few places that are temperate enough to sustain life. And of all of those, it is only planet Earth that seems to strike the careful balance required to sustain it perpetually.
Europa. CThe cracked, icy surface of Europa. The smoothness of the surface has led many scientists to conclude that oceans exist beneath it. Credit: NASA/JPLredit: NASA
Europa, Jupiter’s sixth-closest moon, has long been a source of fascination and wonder for astronomers. Not only is it unique amongst its Jovian peers for having a smooth, ice-covered surface, but it is believed that warm, ocean waters exist beneath that crust – which also makes it a strong candidate for extra-terrestrial life.
And now, combining a mosaic of color images with modern image processing techniques, NASA has produced a new version of what is perhaps the best view of Europa yet. And it is quite simply the closest approximation to what the human eye would see, and the next best thing to seeing it up close.
The high-resolution color image, which shows the largest portion of the moon’s surface, was made from images taken by NASA’s Galileo probe. Using the Solid-State Imaging (SSI) experiment, the craft captured these images during it’s first and fourteenth orbit through the Jupiter system, in 1995 and 1998 respectively.
The view was previously released as a mosaic with lower resolution and strongly enhanced color (as seen on the JPL’s website). To create this new version, the images were assembled into a realistic color view of the surface that approximates how Europa would appear to the human eye.
This newly-reprocessed color view of Europa was made from images taken by NASA’s Galileo spacecraft in the late 1990s. Image credit: NASA/JPL-Caltech/SETI Institute
As shown above, the new image shows the stunning diversity of Europa’s surface geology. Long, linear cracks and ridges crisscross the surface, interrupted by regions of disrupted terrain where the surface ice crust has been broken up and re-frozen into new patterns.
Images taken through near-infrared, green, and violet filters have been combined to produce this view. The images have been corrected for light scattered outside of the image to provide a color correction that is calibrated by wavelength. Gaps in the images have been filled with simulated color based on the color of nearby surface areas with similar terrain types.
These color variations across the surface are associated with differences in geologic feature type and location. For example, areas that appear blue or white contain relatively pure water ice, while reddish and brownish areas include non-ice components in higher concentrations.
The polar regions, visible at the left and right of this view, are noticeably bluer than the more equatorial latitudes, which look more white. This color variation is thought to be due to differences in ice grain size in the two locations.
Artist’s concept of the Galileo space probe passing through the Jupiter system. Credit: NASA
This view of Europa stands out as the color view that shows the largest portion of the moon’s surface at the highest resolution. An earlier, lower-resolution version of the view, published in 2001, featured colors that had been strongly enhanced. Space imaging enthusiasts have produced their own versions of the view using the publicly available data, but NASA has not previously issued its own rendition using near-natural color.
The image also features many long, curving, and linear fractures in the moon’s bright ice shell. Scientists are eager to learn if the reddish-brown fractures, and other markings spattered across the surface, contain clues about the geological history of Europa and the chemistry of the global ocean that is thought to exist beneath the ice.
This is of particular interest to scientists since this supposed ocean is the most promising place in our Solar System, beyond Earth, to look for present-day environments that are suitable for life. The Galileo mission found strong evidence that a subsurface ocean of salty water is in contact with a rocky seafloor. The cycling of material between the ocean and ice shell could potentially provide sources of chemical energy that could sustain simple life forms.
Future missions to Europa, which could involve anything from landers to space penetrators, may finally answer the question of whether or not life exists beyond our small, blue planet. Picturing this world in all of its icy glory is another small step along that path.
In addition to the newly processed image, JPL has released a new video that explains why this likely ocean world is a high priority for future exploration:
