I was thinking, this solar system has 1 possibly 2 plantets in the habitable zone, correct me if I’m wrong. However, there are about 5 or so moons between Jupiter and Saturn that are decent sized, forgive the imprecision.
So, wouldn’t it be most likely to find extra terrestrial life on the moon of a gas giant in a system that has a sun a bit hotter than ours? Is there some reason like tides, planetary eclipses, magnetic fields, orbits or something like that which would make this impossible?
The reason I’m asking is because it seems a whole lot easier for us to find large gas giant planets out there than it is small planets like ours that are closer to their stars.
It’s certainly not impossible, by any means. There’s been some interest in Titan, because it has an atmosphere and liquid oceans, and Europa, because it’s covered in ice, possibly with liquid water underneath.
I’m not an astronomer, so it’s certainly possible that my knowledge is incomplete, but as far as I know, no extrasolar moons have yet been detected, so speculating on what they might be like seems rather pointless to me. I mean, it seems very likely that they exist, but without data, any speculation would be just that - pure speculation.
I have a feeling the following scenario has already been done in a SF short story somewhere. Perhaps the physical constraints (mainly in terms of time) are too tight, maybe not…
In the waning days of the human civilization, a quasi-mad scientist decides to launch a probe, chock full of various Terrestrial microbes, into Titan’s atmosphere (soft landing). He knows that certain bacteria can subsist in a dormant form for very long periods of time (insert Applied Phlebotinum to keep the spores viable for millions of years).
Fast forward: the sun balloons into a red giant, the Earth is fried, but Titan warms up, warm enough for liquid water to form. The capsule containing the spores pops open, they start to grow and thrive, eventually closely following the path that life on Earth took (tho I’m not sure how long the Sun can remain stable in terms of luminosity-as a red giant it might pulsate too much).
A sentient life form evolves, and soon is launching its own probes into what is left of the solar system. It makes note of the fried cinders of Earth and Mars (Mercury and Venus will get swallowed up IIRC), and explores the outer planets, where it finds another capsule on Pluto, detailing the ancient Earth civilization which once lived on the 3rd rock from the sun (now 1st rock), including all the kinds of stuff that Sagan put on the Voyagers, like concerts, pictures, etc.
Well, it sounds like it’s possible. I thought that there might be something like frequent solar eclipses by the gas giant, or something with magnetic fields or atmospheres that would make it impossible, just because the body is a moon. I suppose not.
Side Question: I can see that the average period that Saturn eclipses the Sun on Titan is about six hours, so this probably wouldn’t be an issue. But are orbital periods always directly related to the satellite’s distance from the body? Does a satellite with more kinetic energy/speed automatically move to a higher orbit? I’m wondering because all Galilean Satellites are still quite a bit smaller than Earth, and in order to have one the size of the Earth and dense enough to have a magnetic field, there would need to be a higher orbit, a much slower orbit, a much larger gas planet, or some combination of factors. Would this totally destroy viability?
I’ve never taken an astronautics course, so I don’t know.
The laws of orbital mechanics are strict. Orbital period is uniquely determined by orbital distance, and if you speed up, you will always go to a higher orbit. But there’s no law at all against having something Earth-sized in an orbit like those of Jupiter’s moons.
Continuing this hijack, there are some controversial claims of the revival of ancient bacterial spores from tens (and even hundreds) of millions of years ago. There are also a number of extremophile bacteria that grow and thrive at temperatures below freezing, which might be able to survive and grow on Europa. So you might not even need to break out the Applied Phelbotinum research…
You would have to define what life means to you. Obviously there is nothing as advanced as humans on the moons of our planets, but how low on the “life scale” do you go?
What would be the most complex form of life you’d expect to find? I don’t know but that is the first place to start.
Second you have to think about this, although it’s no means conclusive, many are starting to think life didn’t start just once on Earth. There is evidence (again no by no means definte) that suggests, small uncomplicated forms of life began and died out, then it happened again. This happened a few times before the right combination took off and led here.
Whether or not we find life is really a matter of money. The moon was an achievable goal, I mean moneywise. But other space exploration, manned or not, is going to be subject to much scrutiny. Who wants to spend money to see if there is bacteria on Titan, when we have people dying from TB. You know instead of finding new bacteria, let’s kill the ones that are already giving us grief
One thing you’d have to watch out for is tidal locking. If a moon is close enough to a gas giant, various gravitational forces will cause its rotation rate to match up with its revolution rate, so that the moon always has the same side facing the gas giant. Earth’s Moon is tidally locked with the Earth, for example, as are all four of the Galilean moons of Jupiter. This wouldn’t be disastrous, but it would mean that the “days” and “nights” on such a world would be much longer; the Sun rises on Callisto once every 16 Earth days, for example. This means that the changes in temperature from “noon” to “midnight” would be much greater, which might give our life-forms a bit of trouble.
there’s also Jupiter’s magnetosphere as an issue, isn’t there? that it’s too high voltage (excuse my non technical term) for humans to live on a galielan moon?
For a fictional treatment of the issue, there’s always “Farmer in the Sky”, by Heinlein.
Of course, we’re unlikely to learn anything definitive about the presence (or absence) of life on Europa, as attempting a landing there would be imprudent.