PDA

View Full Version : Could a gas planet ever get depleted?



theant4
2017-Jan-13, 07:13 PM
Is there any sort of continuous production of gasses on a planet like Jupiter, or is the composition of the atmosphere just kind of fixed? If a planet like that were the subject of a gas mining operation in a sci fi story (think Bespin in Star Wars), would the gasses eventually be depleted, or would they be able to regenerate somehow? Or do we even know?

In the event that they were eventually depleted, I'd think that might gradually affect the planet's atmospheric/gravitational stability and would screw up any moons or space stations orbiting it (and then of course kill the planet itself).

Roger E. Moore
2017-Jan-13, 07:47 PM
The only way in practical terms that a gas giant could be depleted (so far as I know) is from solar heating, as for a hot Jupiter whose atmosphere blows off into a heliocentric ring.

theant4
2017-Jan-13, 07:55 PM
So if there was some sort of sci fi mining operation removing gas from the atmosphere in modest quantities, would the planet be able to replenish itself? Or would that gas just be gone? Because I feel like if a mining operation like that went on for long enough (and it probably would take a long time), it would eventually have adverse effects on the planet.

Darrell
2017-Jan-13, 08:40 PM
Planets of any kind accrete additional mass over time by the simple mechanism of running into other material in space, from individual particles up to large bodies like comets, asteroids and in extreme cases other planet size bodies. But, except in the rare cases of very large impacts, this steady accumulation of in-falling matter is not significant compared to the size of the planet. Other than that there is no mechanism known that could generate new mass within a planet. Gasses could be replenished by natural processes, such as changes of state or chemical reactions, but only to the limit of the materials the planet has to start with.

If your mining operation is on a large enough scale it could certainly deplete a gas giant planet, but you are talking very large scale to have a significant depletion of gas. If the operation were large enough scale to cause a significant change in the mass of the planet, and there doesn't seem to be any reason why it couldn't be in principle, then yes, that would affect the orbits of everything around the planet.

publiusr
2017-Jan-13, 09:12 PM
The Jupiter Theft...

DaveC426913
2017-Jan-14, 05:07 PM
The Jupiter Theft...

Good book. :)

DaveC426913
2017-Jan-14, 05:11 PM
If the operation were large enough scale to cause a significant change in the mass of the planet, and there doesn't seem to be any reason why it couldn't be in principle, then yes, that would affect the orbits of everything around the planet.

And at this scale, you might also want to consider how that mass is being redistributed around the solar system.
Is it increasing the mass of other planets?
It is being distributed thinly about the SS as reaction mass?
Is it leaving the system in the tanks of interstellar craft?

Glom
2017-Jan-14, 11:14 PM
Think it might have been The Complete Cosmos which had a rendering of what would happen when the Sun runs out of hydrogen and pitches a fit. It would allegedly denude Jupiter quite severely.

speach
2017-Jan-14, 11:27 PM
So if there was some sort of sci fi mining operation removing gas from the atmosphere in modest quantities, would the planet be able to replenish itself? Or would that gas just be gone? Because I feel like if a mining operation like that went on for long enough (and it probably would take a long time), it would eventually have adverse effects on the planet.

But the amount that needs to be taken from say Jupiter would have to be enormous to have any lasting effect

Ara Pacis
2017-Jan-19, 05:37 AM
To Expand on what Darrell wrote, the removal of mass would remove mass. However, if the gas giant has liquid oceans of the same sort of element, then the liquid could turn to gas to make up for the gas that was removed. For example, water boils at a lower temperature when the pressure is lower (hence different cooking instructions for Denver, Colorado).

CJSF
2017-Jan-19, 06:13 AM
To Expand on what Darrell wrote, the removal of mass would remove mass. However, if the gas giant has liquid oceans of the same sort of element, then the liquid could turn to gas to make up for the gas that was removed. For example, water boils at a lower temperature when the pressure is lower (hence different cooking instructions for Denver, Colorado).

Yes, but the mass wouldn't change, just the average density.

CJSF

Jens
2017-Jan-19, 06:48 AM
It's important to note that there can be no process of regeneration. If you mine more quickly that the planet gains mass from falling dust, then it will lose mass, period. You can't create something out of nothing, it's the law actually.

Also, it will affect the orbits of moons and space stations, but not catastrophically.

Noclevername
2017-Jan-19, 07:39 AM
As far as orbits go, any civilization (or series of many civilizations) that has the capacity to tap a gas giant on a large scale, could certainly adjust the orbits of moons as well.

Killing the planet might be harder, as Jovian planets have cores of heavy elements, which will remain behind after the gas is gone. If the Sun is still around then, you might even terraform the newly terrestrial planet. (Assuming the effects of pressure release leave its exposed surface viably stable.)

Ara Pacis
2017-Jan-19, 05:13 PM
Yes, but the mass wouldn't change, just the average density.

CJSF

Eh? The mass changes when it's removed. The OP was asking about regenerating gas not mass.

CJSF
2017-Jan-19, 05:36 PM
Sorry, I knew that. I thought you were saying something else, and I was medicated at the time! I think I meant, the mass of the remaining planet wouldn't change with the conversion to gas, but the density would. Which is sort of not relevant. Don't post under the influence, they say!

CJSF