Jupiter’s icy moon Europa. Credits: NASA/Jet Propulsion Laboratory, SETI Institute
Jupiter‘s four largest moons – aka. the Galilean Moons, consisting of Io, Europa, Ganymede, and Callisto – are nothing if not fascinating. Ever since their discovery over four centuries ago, these moons have been a source of many great discoveries. These include the possibility of internal oceans, the presence of atmospheres, volcanic activity, a magnetosphere (Ganymede), and the possibility of having more water than Earth.
But arguably, the most fascinating of the Galilean Moons is Europa: the sixth closest moon to Jupiter, the smallest of the four, and the sixth-largest moon in the Solar System. In addition to having an icy surface and a possible warm-water interior, this moon is considered to be one of the most likely places for finding life beyond Earth.
Illustration of Jupiter and the Galilean satellites. Credit: NASA
It’s no accident that Jupiter shares its name with the king of the gods. In addition to being the largest planet in our Solar System – with two and a half times the mass of all the other planets combined – it is also home to some of the largest moons of any Solar planet. Jupiter’s largest moons are known as the Galileans, all of which were discovered by Galileo Galilei and named in his honor.
They include Io, Europa, Ganymede, and Callisto, and are the Solar System’s fourth, sixth, first and third largest satellites, respectively. Together, they contain almost 99.999% of the total mass in orbit around Jupiter, and range from being 400,000 and 2,000,000 km from the planet. Outside of the Sun and eight planets, they are also among the most massive objects in the Solar System, with radii larger than any of the dwarf planets.
When humans finally travel into space, where will we live? Will we ever be able to colonize gas giants like Jupiter?
NASA and Elon Musk have plans to get your ass to Mars.
It’s not impossible to imagine humans living and working on the Red Planet. Maybe they’ll be crusty asteroid miners making their fortune digging precious minerals out of the inexhaustible supply of space rocks. Pray they don’t dig too deeply. We should go ask Kuato, that creepy little guy knows everything! Except he’s always trying to get you to touch his funny little hands. Pass.
Venus looks like it’s a pretty great place to live, if we stick to the clouds in floating sky cities, plying the jet streams in our steampunk dirigibles. It’ll be fun, but first, does anyone know how to attach a cog to a top hat? Venus, here we come!
We should stay away from the surface, though, that place’ll kill you dead. We’re guessing a crispy shell holding in a gooey center, at least for the first few moments. Once we sort the living in space deal, is there anywhere we won’t be able to go?
We could create underwater cities on Europa or Ganymede, in the vast oceans with the exotic hopefully unarmed, peaceful, vegetarian Jovian whales.Like Jupiter? Could we live there?
Jupiter is the most massive planet in the Solar System. It has a diameter of almost 140,000 kilometers and it’s made mostly of hydrogen and helium; the same materials of the Sun. It has more than 317 times the mass of the Earth, providing its enormous gravity.
If you could stand on the cloud tops of Jupiter, you would experience 2.5 times the gravity that you experience on Earth. Then you’d fall to your death, because it’s a gas planet, made of hydrogen, the lightest element in the Universe. You can’t stand on gas, rookie.
If you tried to bring your Venusian Vernian exploratorium ballooncraft for a jaunt across the skies of Jupiter, it would sink like a copper bowler with lead goggles.
The only thing that’s lighter than hydrogen is hot hydrogen. Let’s say you could make a balloon, and fill it with superheated hydrogen and float around the cloud tops of Jupiter suffering the crushing gravity. Is there anything else that might kill you?
Did you leave Earth? Then of course there is. Everything is going to kill you, always. You might want to write that on the brass plaque next to your ship’s wheel with the carving of Shiva in the center there, Captain Baron Cogsworth Copperglass.
Jupiter’s Great Red Spot and Ganymede’s Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)
Jupiter is surrounded by an enormous magnetic field, ten times more powerful than Earth’s. It traps particles and then whips them around like an accelerator. This radiation is a million times more powerful than the Earth’s Van Allen belts. Our big human meat roasting concern during the Apollo days.
If you tried to get near the radiation belts without insufficient shielding. It’d be bad. Just picture jamming your copper and brass steamwork fantasy into a giant microwave.
Is it possible there’s a solid core, deep down within Jupiter? Somewhere we could live, and not have to worry about those pesky buoyancy problems? Probably. Astronomers think there are a few times the mass of the Earth in rocky material deep down inside.
Of course, the pressure and temperature are incomprehensible. The temperature at the core of Jupiter is thought to be 24,000 degrees Celsius. Hydrogen is crushed so tightly it becomes superheated liquid or strange new flavors of ice. It becomes a metal.
The moral, we’re not equipped to go there. Let alone set up shop. So, let’s just stick with fantasizing your adventures as Emperor Esquire Beardweirdy Brassnozzle Steamypantaloons.
In his classic book 2001, Arthur C. Clarke said that “all these worlds are yours except Europa, attempt no landing there”. Well that’s crazy.
Europa’s awesome, we’re totally landing there, especially if we discover alien whales. So, Europa first. Besides, it’s just a book. So, Jupiter is the worst. Do not navigate your airship into that harbour.
What’s the worst possible environment you can imagine to try and live on? Tell us in the comments below.
A full Moon flyby, as seen from Paris, France. Credit and copyright: Sebastien Lebrigand.
Shining like a beacon in Earth’s sky is the Moon. We’ve seen so much of it in our lifetimes that it’s easy to take it for granted; even the human landings on the Moon in the 1960s and 1970s were eventually taken for granted by the public.
Fortunately for science, we haven’t stopped looking at the Moon in the decades after Neil Armstrong took his first step. Here are a few things to consider about Earth’s closest big neighbor.
A montage of images taken of Jupiter and its moon Io (foreground) by the New Horizons mission in 2007. Jupiter is shown in infrared wavelengths while Io is close to true-color. On top of Io is an eruption from the volcano Tvashtar. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
New Horizons, you gotta wake up this weekend. There’s so much work ahead of you when you reach Pluto next year! The spacecraft has been sleeping quietly for weeks in its last great hibernation before the dwarf planet close encounter in July. On Saturday (Dec. 6), the NASA craft will open its eyes and begin preparations for that flyby.
How cool will those closeups of Pluto and its moons look? A hint comes from a swing New Horizons took by Jupiter in 2007 en route. It caught a huge volcanic plume erupting off of the moon Io, picked up new details in Jupiter’s atmosphere and gave scientists a close-up of a mysterious “Little Red Spot.” Get a taste of the fun seven years ago in the gallery below.
An eruption from the Tvashtar volcano on Io, Jupiter’s moon, in several different wavelength images taken by the New Horizons spacecraft in 2007. The left image from the Long Range Reconnaissance Imager (LORRI) shows lava glowing in the night. At top right, the Multispectral Visible Imaging Camera (MVIC) spotted sulfur and sulfor dioxide deposits on the sunny side of Io. The remaining image from the Linear Etalon Imaging Spectral Array (LEISA) shows volcanic hotspots on Io’s surface. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Jupiter’s “Little Red Spot” seen by the New Horizons spacecraft in 2007. The spot turned red in 2005 for reasons scientists were then unsure of, but speculated it could be due to stuff from inside the atmosphere being stirred up by a storm surge. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
A “family portrait” of the four Galilean satellites around Jupiter taken by the New Horizons spacecraft and released in 2007. From left, the montage includes Io, Europa, Ganymede and Callisto. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
A composite of Jupiter’s bands (and atmospheric structures) taken in several images by the New Horizons Multispectral Visual Imaging Camera, showing differences due to sunlight and wind. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
In February and March 2007, a huge plume erupted from the Tvashtar volcano on Jupiter’s moon Io. The image sequence taken by New Horizons showed the largest such explosion then viewed by a spacecraft — even accounting for the Galileo spacecraft that examined Io between 1996 and 2001. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
The New Horizons flyby of Io in 2007 (right) revealed a changing feature on the surface of the Jupiter moon since Galileo’s image of 1999 (left.) Inside the circle, a new volcanic eruption spewed material; other pictures showed this region was still active. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Artist's impression of the Jupiter Icy Moons Explorer (JUICE) near Jupiter and one of its moons, Europa. Credit: ESA/AOES
It takes years of painstaking work to get a spacecraft off the ground. So when you have a spacecraft like JUICE (the Jupiter Icy Moons Explorer) set to launch in 2022, you need to back up about a decade to get things figured out. How will the spacecraft get there? What science instruments will it carry? What will the spacecraft look like and what systems will support its work?
JUICE just hit another milestone in its development a few days ago, when the European Space Agency gave the go-ahead for the “implementation phase” — the part where the spacecraft design begins to take shape. The major goal of the mission will be to better understand those moons around Jupiter that could be host to life.
The spacecraft will reach Jupiter’s system in 2030 and begin with observations of the mighty planet — the biggest in our Solar System — to learn more about the gas giant’s atmosphere, faint rings and magnetic environment. It also will be responsible for teaching us more about Europa (an icy world that could host a global ocean) and Callisto (a moon pockmarked with the most craters of anything in the Solar System.)
Its major departure from past missions, though, will come when JUICE enters orbit around Ganymede. This will the first time any spacecraft has circled an icy moon repeatedly; past views of the moon have only come through flybys by the passing-through spacecraft (such as Pioneer and Voyager) and the Galileo mission, which stuck around Jupiter’s system in the 1990s and early 2000s.
Ganymede Credit: NASA
With Ganymede, another moon thought to host a global ocean, JUICE will examine its surface and insides. What makes the moon unique in our neighborhood is its ability to create its own magnetic field, which creates interesting effects when it interacts with Jupiter’s intense magnetic environment.
“Jupiter’s diverse Galilean moons – volcanic Io, icy Europa and rock-ice Ganymede and Callisto – make the Jovian system a miniature Solar System in its own right,” the European Space Agency stated when the mission was selected in 2012.
“With Europa, Ganymede and Callisto all thought to host internal oceans, the mission will study the moons as potential habitats for life, addressing two key themes of cosmic vision: what are the conditions for planet formation and the emergence of life, and how does the Solar System work?”
Jupiter's Great Red Spot and Ganymede's Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)
Halloween is just around the corner. And in what appears to be an act of cosmic convergence, Hubble captured a spooky image of Jupiter staring back at us with a cyclops eye!
While this is merely a convenient illusion caused by the passage of Ganymede in front of Jupiter – something it does on a regular basis – the timing and appearance are perfect.
