Looking at Europa it seems possible that moons of gas giants can support liquid water and maybe even life, but is it scientifically possible for moons orbiting gas giants to have earth like atmospheres and environments? What about a moon of a gas giant orbiting around a binary system?
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Nothing at all precluding the possibility. A gas giant would cause the planets to have MUCH larger tides then Earth has, and if it was a Jovian-type planet, if the moon didn't have a magnetosphere the radiation levels would likely be very high. But if it was a Saturn-like planet with an Earth-like moon... nope, nothing at all precluding the possibility.
Same goes for binary systems, just all depends on distances.
Same goes for binary systems, just all depends on distances.
Tidal flexing could be a serious problem, though.
A magnetic field would likely also be desirable, which I think would require a different sort of core than one is likely to find with a gas giant moon.
A magnetic field would likely also be desirable, which I think would require a different sort of core than one is likely to find with a gas giant moon.
thnkrx":3ruuvf1h said:
Tidal flexing is negligible on Callisto or Iapetus.
Ganymede has a molten core and a magnetic field.
Most importantly, all Galilean moons are far within Jupiter's magnetosphere, and so are shielded from Solar Wind. So is Titan within Satrun's magnetosphere.
h2ouniverse":3hs8ua4x said:
A gas giant magnetosphere may shield from Solar Wind. It can also give troublesome Van Allen belts.
h2ouniverse":3mjq3y0a said:
Unfortunately, the surfaces of the Galilean moons are bathed in huge amounts of lethal radiation from Jupiter's powerful magnetic field, so the fact that they are protected from the solar wind is moot. Any earth-like world orbiting a gas giant would have to have a powerful magnetosphere of it's own to deflect the radiation, and a thick atmosphere to help shield any life forms on the surface from energetic particles. If it was too close to it's primary, it may be subjected to considerable tidal flexing, giving it a surface with catastrophic amounts of tectonic activity. If it was too far away, it would have a very long day/night cycle, since all such worlds would most likely have a rotation synchronized to it's orbital period, and that could be problematic for life as well.
That is what I was getting at.
One other thing I've wondered about in conjunction with this: yes, a number of the gas giant moons in this solar system are fairly sizable - bigger than earths moon, in fact. Yet, if memory serves, they also tend to have a much lower mass than do planets of roughly comparable size. So...way back when things are first forming up in a solar system, what would there be be to stop a more or less earth mass 'moon' from accumulating gasses and turning into a Neptune style gas giant in its own right? Seems to me there would have to be some sort of 'upper mass limit' for a gas giant moon to prevent this from happening. The question then would become is that limit high enough up to permit the moon in question to develop and retain an earthlike atmosphere.
The limit is the larger gas giant planet nearby. The planet has much more gravity, so material that would otherwise wind up on the moon, instead is absorbed onto the parent planet. STuff has be be really close to wind up as part of the moon.
To Crazyeddie and Thnkrx
Io and Europa are in Jupiter's radiations belts, granted.
But radiation at Ganymede is much milder (partly thanks to its own magnetic field). And there is even less at Callisto.
And Saturn, Neptune and Uranus have not such violent radiation belts.
Titan suffers little radiation from Saturn and has a thick atmosphere hence no radiation on ground. Triton suffers nothing at all (excepted from being in a very cold place, enough to condensate nitrogen).
A long day duration is not an issue if the atmosphere is thick enough, as it will smoothen day/night temperature variations.
What the recent discoveries at exoplanets have shown is that many, many combinations are possible. The only rules should be humility and imagination. Ruling out any combination (such as large moon with molten core, mag field and thick atmosphere, around a giant in the habitable zone) would be particularly unwise.
Best regards.
Io and Europa are in Jupiter's radiations belts, granted.
But radiation at Ganymede is much milder (partly thanks to its own magnetic field). And there is even less at Callisto.
And Saturn, Neptune and Uranus have not such violent radiation belts.
Titan suffers little radiation from Saturn and has a thick atmosphere hence no radiation on ground. Triton suffers nothing at all (excepted from being in a very cold place, enough to condensate nitrogen).
A long day duration is not an issue if the atmosphere is thick enough, as it will smoothen day/night temperature variations.
What the recent discoveries at exoplanets have shown is that many, many combinations are possible. The only rules should be humility and imagination. Ruling out any combination (such as large moon with molten core, mag field and thick atmosphere, around a giant in the habitable zone) would be particularly unwise.
Best regards.
Within the solar system, the best thing may have been
to dump large amounts of bacteria and other organisms
on every moon and planet that had a slight chance of supporting life,
to wait years and decades, and check them time and again to see how life evolves elsewhere.
(I know most of the bacteria and organisms would probably not last very long, but scientists on earth
experiment with mice and organisms anyway. Scientists should have done this back in the days of the
Pioneer and Voyager launches.)
to dump large amounts of bacteria and other organisms
on every moon and planet that had a slight chance of supporting life,
to wait years and decades, and check them time and again to see how life evolves elsewhere.
(I know most of the bacteria and organisms would probably not last very long, but scientists on earth
experiment with mice and organisms anyway. Scientists should have done this back in the days of the
Pioneer and Voyager launches.)
h2ouniverse":r1o7ibd7 said:
True. Gas Giant doesn't necessarily mean fierce radiation belts.
h2ouniverse":r1o7ibd7 said:
And just because a moon is tidelocked doesn't mean it has to have a very long day. The day of a tide locked moon would be the same as it's orbital period about the gas giant. Mimas has about a 24 hour orbit about Saturn.
h2ouniverse":r1o7ibd7 said:
That sounds reasonable to me.
Above is my rendition of an artifact discovered at the L4 of GIELO (Giant In Earth Like Orbit) and ELM (Earth Like Moon).
A star ship sends out quad pod scout ships to investigate the object. GIELO can be seen in the background on the left and ELM is in the upper right.
Wouldn't earthlike planetoids orbiting giants have a much higher rate of impact from
life-disrupting bolides?
life-disrupting bolides?
There are many giants exoplanets within the habitable zone of their stars. There are searches on to try and detect exo-moons. The method uses changes in the duration and timing of planet transits, and can potentially detect an earth mass exo-moon. Fingers crossed, but it's probably just a matter of time till one is discovered.
Couple of tweaks in information:
Yes the outer moons of the solar system are low mass for their size if they were made only of rock like the moon. However, they have a large amount of water (ice and liquid : most likely). The magnetic field of Ganymede, Callisto and Europa(possible field) are likely due to the salty ocean rather than a molten liquid iron core as on earth. They are not dense enough to have large amounts of iron, they are too small to retain heat, and tidal flexing is not enough except for Europa to melt much of the core.
The size of tides (not flexing) depends both on masses involved and their separation. The Moon is actually very close to the Earth compared to other large moons. The tides would increase as with mass of planet, and decrease with the distance cubed.
There is no obvious upper limit to the mass of the moon, compared to planet. eg Earth-Moon, Pluto-Charon. In principle you could have a two objects about the same mass/size.
Couple of tweaks in information:
Yes the outer moons of the solar system are low mass for their size if they were made only of rock like the moon. However, they have a large amount of water (ice and liquid : most likely). The magnetic field of Ganymede, Callisto and Europa(possible field) are likely due to the salty ocean rather than a molten liquid iron core as on earth. They are not dense enough to have large amounts of iron, they are too small to retain heat, and tidal flexing is not enough except for Europa to melt much of the core.
The size of tides (not flexing) depends both on masses involved and their separation. The Moon is actually very close to the Earth compared to other large moons. The tides would increase as with mass of planet, and decrease with the distance cubed.
There is no obvious upper limit to the mass of the moon, compared to planet. eg Earth-Moon, Pluto-Charon. In principle you could have a two objects about the same mass/size.
What if there were caves and such on the moon. "Surface life" could take refuge in them. Then maybee the radiation
could supply energy indirectly. I don't know how the life forms would get from one island cave system to the next
maybee if they went really fast? Flew? Swam. On earth the organisms have constructed a useful atm of O2. Would
it be possible that organism on a moon "constructed" a giant magnetic field? Are you shure earth's magnetic field
was not enhanced by the moon forming event in which apparently the iron nickel core of the impactor was absorbed
into the core of the earth? Perhaps a gas giant moon could also receive such a core.
could supply energy indirectly. I don't know how the life forms would get from one island cave system to the next
maybee if they went really fast? Flew? Swam. On earth the organisms have constructed a useful atm of O2. Would
it be possible that organism on a moon "constructed" a giant magnetic field? Are you shure earth's magnetic field
was not enhanced by the moon forming event in which apparently the iron nickel core of the impactor was absorbed
into the core of the earth? Perhaps a gas giant moon could also receive such a core.
Radiation apparently does not prevent life. Humans may not survive radiation unprotected, but
here is an interesting article:
http://science.nasa.gov/newhome/headlines/ast01sep98_1.htm#anchor179666
It also mentions viable bacteria collected from the interior of an operating nuclear reactor.
here is an interesting article:
http://science.nasa.gov/newhome/headlines/ast01sep98_1.htm#anchor179666
It also mentions viable bacteria collected from the interior of an operating nuclear reactor.
Did a little reading up on planetary and satelite magnetic fields. What it comes down to is weather the core of the planet/satelite has a liquid core, (outer core). Has circulation . And has convection.
Now, Venus has all this but convection, which it could have had and might have in the future, but at present does not have, and so does not generate a significant magnetic field.
Mercury, does have a rather large core, and does have a magnetic field at its surface wich is 1% of earth's. Weather, this is do to a molten core is not clear to me. Is !% enough to shield from radiation? The way I see it is that if we
reduce earths magnetic field to !% its current level, roughly 100x as much radiation would reach the surface of earth,
wich would still be completly safe. So is it then safe to stand on Mercury (dark side) with out radiation shielding?
Io, apparently has all the requirements to generate a magnetic field, but has no convection. Since, when the Galilaoe
spacecraft attempted to measure its magnetic field it got zero.
Now, if you had a moon as sort of a hybrid between Europa and Io, and maybee a bit Bigger, It is COMPLETLY LIKELY
THAT THE MOON COULD GENERATE A POWERFUL MAGNETIC FIELD.
Now, Venus has all this but convection, which it could have had and might have in the future, but at present does not have, and so does not generate a significant magnetic field.
Mercury, does have a rather large core, and does have a magnetic field at its surface wich is 1% of earth's. Weather, this is do to a molten core is not clear to me. Is !% enough to shield from radiation? The way I see it is that if we
reduce earths magnetic field to !% its current level, roughly 100x as much radiation would reach the surface of earth,
wich would still be completly safe. So is it then safe to stand on Mercury (dark side) with out radiation shielding?
Io, apparently has all the requirements to generate a magnetic field, but has no convection. Since, when the Galilaoe
spacecraft attempted to measure its magnetic field it got zero.
Now, if you had a moon as sort of a hybrid between Europa and Io, and maybee a bit Bigger, It is COMPLETLY LIKELY
THAT THE MOON COULD GENERATE A POWERFUL MAGNETIC FIELD.
Agreed. Though the moon would still have to have sufficient mass to retain an oxygen/nitrogen atmosphere and orbit far enough out from the gas giant to offset the worst of the tidal flexing.
The protective magnetic field is more important than the mass/density of the satelite.
Mars has a considerable atmosphere, but it would be significantly thicker if the planet had
not lost its magnetosphere. As it is now the pressure is 1 KPa at the lowest point on Mars.
Compare that with Earth's 1000 KPa mean surface presure, which is significant. Now, Earth's 1000 KPa is much more than is neccesarry to have liquid water. 6 KPa is just anough pressure to have pure liquid water. Maybee 5 KPa for a satured CaCl2 solution.
Mars, is 1/10 the mass of Earth, Mercury is 1/20 Earth's mass. But the escape volocities are both about half of Earth's. But, Earth's oxygen and nitrogen are firmly within earth's grip. So, an object like Mars or Mercury placed in orbit around jupiter likely would be able to retain an atmosphere sufficiently pressurized to sustain a liquid surface. Take away earth's magnetosphere and shurly the atmoshere would be striped away from the planey in a few million years. It would turn into a Mars.
Mars has a considerable atmosphere, but it would be significantly thicker if the planet had
not lost its magnetosphere. As it is now the pressure is 1 KPa at the lowest point on Mars.
Compare that with Earth's 1000 KPa mean surface presure, which is significant. Now, Earth's 1000 KPa is much more than is neccesarry to have liquid water. 6 KPa is just anough pressure to have pure liquid water. Maybee 5 KPa for a satured CaCl2 solution.
Mars, is 1/10 the mass of Earth, Mercury is 1/20 Earth's mass. But the escape volocities are both about half of Earth's. But, Earth's oxygen and nitrogen are firmly within earth's grip. So, an object like Mars or Mercury placed in orbit around jupiter likely would be able to retain an atmosphere sufficiently pressurized to sustain a liquid surface. Take away earth's magnetosphere and shurly the atmoshere would be striped away from the planey in a few million years. It would turn into a Mars.
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