which Galilean moon?

Question

is most likely to support life?
Explain your reasoning...

MOST likely...

Answer 1

Depends on your point of view - but there are two likely candidates

Ganymede : Oxygen Atmosphere, ice caps at the poles (water), large land mass and a magnetic field (much like earths).

Europa : massive ice crusted sea - possibly supporting deep sea life similar to that at the bottom of our own sea.

the other two - little or no chance

io : very much like earth when it was first forming - one very large volcano!

Callisto : another ocean moon - however with a carbon dioxide atmosphere, less hospitable than its two neighbours.

Personally, i'd say Europa is the best for currently supporting life, but id say Ganymede would be best of the moons for attempted population

Answer 2

Europa will be alive, I'll place the odds at 95%.

Europa has all the necessary ingredients, liquid water, organic chemistry and available energy sources. Of the 4 Galilean moons, she should be the easiest to access (her biosphere/ocean). The ice crust is probably no more than 10 miles thick (perhaps much thinner in spots) atop a 100 mile deep ocean. More water than in all the earth's oceans put together! We need to send an orbiter there to firm up these numbers, obviously.

Europa gets about a tenth of the tidal-flexing energy from Jupiter that her sister Io gets, which is still a substantial amount, enough for ADVANCED, multi-cellular flora and fauna. NOT just microbes. Black smoker communities. At the very least.

Fish? Whales? Nessies??? Who knows, I hope I get to find out.

Ganymede and Callisto probably have seas rather than oceans, 100 miles under the ice crust, much harder to access and much less tidal energy. I give odds of 75% for life and 100 years for the technology to sample it.

BUT the next planet over (Saturn) has a little moon, Enceladus, which may have a biosphere/sea of liquid water that may be even easier to access than Europa; a STARDUST type spacecraft could zip through the water geysers (spouting out microbes???), scoop up a sample and bring it back to Earth! We could have a sample in 10 years!

Answer 3

Astronomers generally agree that Europa poses as a strong candidate for that.

Europa's surface is covered in thick ice and there is water under it. We assume that life might exist underneath the surface especially around thermal vents, in the same way that life might exist in lake Vostok in Antarctica that is completely sealed off from the external world for thousands of years.

To see how important this is for science, probes and whatever we send to explore Jupiter and its moons are forbidden from approaching Europa for fear of contaminating this moon with Earthly bacteria. In the same way we forbid drilling in lake Vostok, so that this unique environment remains preserved and uncontaminated with outside bacteria while drilling.

Answer 4

Yipe. I've never understood why somebody would want to invent facts like that. As you can quickly confirm with a trip to the library, neither Ganymede nor Callisto have noticable atmospheres of any sort. The oxygen envelope you hear about is so thin as to be barely distinguishable from the hard vacuum of interplanetary space.

The only Galilean moon that has something that somebody MIGHT call at atmosphere is Io, in part perhaps due in part to the incredible rate of volcanic activity on that body (it turns itself completely inside out about once every 125 years, I recall), but also due to sputtering. Io is within Jupiter's radiation belt, and charged particles trapped within it smack into Io's surface with enough force to knock atoms loose. If none of this makes Io sound very hospitable, it isn't.

The place is covered with lakes of molten sulfur hot enough to glow in daylight, is bathed in enough radiation to kill anybody foolish enough to linger and lucky enough to not get burned alive, and the place has an "atmosphere" only in about the same sense that a comet does. We're looking at a thin cloud of ionized gas escaping into space, albeit not all of it escaping very far on a planetary scale, as Jupiter's gravity creates a gas torus centered on Io's orbit. Nevertheless, if you were there, you wouldn't be able to tell the difference between that "atmosphere" and a vacuum without the use of instruments. You would be disappointed if you were expecting to feel the wind pushing against your suit, or see clouds overhead, or find any signs of what most people would consider to be a real atmosphere.

Forget about life on Io. The place isn't even recommended for visits by astronauts.

Europa looks a little more promising, those not as promising as some like to sell it as being. I'm sure you'll read about deep sea volcanic vent ecosystems and the likelihood of there being volcanos at the bottom of the Europan ocean existing beneath that moon's crust (probably, judging from the resemblance of the landforms on Europa to those seen on oceanic ice packs as seen on Earth). What usually gets glossed over is the fact that those ecosystems do not exist in isolation. Oxygen from the surface does find its way into the deep ocean, and the life found at those deep sea vents is dependent on the oxygen, which is liberated by processed powered by sunlight. Europa is a better candidate than the almost clearly hopeless Io, but it's still not a good one.

It is, however, the best of the bunch if I understand correctly. Ganymede and Callisto might have subsurface oceans as well, but keep in mind the fact that those oceans are kept warm by tidal flexing of the crusts of the moons in question. Picture taking a rigid object and slamming it really hard over and over - it's going to warm up. That's what the tides are doing to the Galilean moons, which are insanely close to a planet hundreds of times more massive than earth, and to each other, enough that the crust of Io flexes - was it sixty miles per day, going up and down? The closer a moon is to Jupiter, the greater the heating afforded by tidal flexing, so the interiors of Ganymede and Callisto aren't likely to be as well heated as that of Europa, which in turn clearly isn't as well heated as that of Io, which boiled its own water off into space long ago.

About the best hope for life on Europa is that one could, perhaps, find photosynthetic organisms living under some of the visible cracks in the surface, over which the ice would be much thinner, maybe thin enough to let light trickle through. On Ganymede, however, a cooler subsurface ocean would make for a thicker crust, making that scenario much less likely. Consider the fact that one find mountains on Ganymede

http://www.pa.msu.edu/courses/1999fall/ISP205/sec-3/galilean_moons_surfaces.html

something that the crust on a body like Europa would lack the strength to support. Such surface rigidity speaks poorly of the likelihood of finding thin spots in the surface ice, which on Ganymede takes on the role that rock serves in the crust of the earth. Figure that anything below somewhere around 130 feet is in eternal night in Earth's Oceans, and you'll see just how thin that patch in the ice has to be for photosynthesis to have a chance.

Conclusion; Ganymede, I seriously doubt it, and since Callisto is likely to be even colder inside, I doubt that life will be found there, even more. I could be pleasantly surprised, but I'd be very surprised if I was.

Answer 5

For a place to support life, it needs liquid water.

Answer 6

mostly Europa.
it is beleived that under its iced surface there is a liquid ocean.