Re: Most Earthlike possible planet around Jupiter


Mike Williams kirjutas:
Wasn't it who wrote:
Clear the pesky moons out of the way, and put an Earth-sized planet in
orbit around Jupiter.

How Earthlike can we get it?

-- If we stick it in Io's orbit, we'll get lots of volcanic activity.
So, a C02-rich atmosphere much denser than Earth's is possible.

Io's mean surface temperature is around -150 C, not counting the hot
spots from volcanic activity.

You only get all that volcanic activity on Io because of the changing
gravity as the other moons go past causing internal heating. If you
clear the other moons out of the way, then you lose that effect.

To get the effect back, you not only need to put the "pesky moons" back,
but you need to put back ones that are larger or closer to achieve the
effect on a larger body.

You might also consider spinning the planet, or putting it into a highly
elliptical orbit so that the tides from Jupiter vary in orientation or
strength. Both of those situations will decay over time as the kinetic
energy gets converted into heat within the planet.

The moons do stabilize elliptic orbit of Io, but would not stabilize
spinning the planet. I think Io is active because Europa is not merely
nearby - it is almost as far from Io as the Moon is from Earth - but
it is in resonant orbit. If the orbits were not resonant then Io would
adopt a much more circular orbit with much less internal heat.

So you can't just naturally find a planet in such a situation, somebody has to put it
there and spin it back up every now and again.

Whereas Io and Europa resonance is natural.

Curiously, no inner satellite of Saturn is quite as active as Io.

You might even consider spinning the planet backwards, so that one side
always faces the Sun. The side of the planet that gets constant sunlight
will be a few degrees warmer. Once again, that configuration is not
stable, so whoever put the planet there in the first place has to keep
coming back and winding it up.

It's probably easier not to wind it up, but to add heat by some other
mechanism, such as giant solar mirrors. However, that sort of thing
would be easier to do with Mars than with a planet that orbits Jupiter.

Giant solar mirrors are unnatural and hard to accomplish.

It is not by awfully large margin that the Galilean moons lack
atmosphere. Titan, only slightly colder, keeps a massive one.

Intense interior heating might not stop carbon dioxide from freezing
away from volcanic centres, but it would prevent carbon dioxide from
staying locked in carbonates. Assuming the position of Io, how much
greenhouse warming could a dense carbon dioxide atmosphere give?

.

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