How much mass would you need to add to the moon to hold any real kind of atmosphere

fligmin

I just had a strange thought while doing my space exploration reading. The question should really be. Is it possible, Say 1000 years in the future, To slowly drop astroids on the lunar surface and gradualy increase its mas to the point it could hold a light atmosphere. That's imagining they, AT that time Had the ability to give it an artificial magnetic field to stop the sun from stripping it.

Just wondering.

By the way Nice letter from the science community

GatheringKnowledge

Mars has bigger mass, than Earth and yet it has much less dense/thick atmosphere, than our planet. Also Titan (a moon of Saturn) has an atmosphere with density higher than on the Earth's surface (~1,4 bars). To answer your question, we would have to completely exclude the influence of solar wind and magnetic fields - and in such case, someone smarter than me would have to answer you

oz93666

Mars has bigger mass, than Earth and yet it has much less dense/thick atmosphere, than our planet. Also Titan (a moon of Saturn) has an atmosphere with density higher than on the Earth's surface (~1,4 bars). To answer your question, we would have to completely exclude the influence of solar wind and magnetic fields - and in such case, someone smarter than me would have to answer you
That's not so ...From Search ... "Mars' mass is 6.42 x 1023 kilograms, about 10 times less than Earth. This affects the force of gravity. Gravity on Mars is 38 percent of Earth's gravity, so a 100-pound person on Earth would weigh 38 pounds on Mars ..."

To answer the original question let's first ignore the solar wind ....

Mass of the body is not the only factor ....High Density allows high surface gravity which is what holds an atmosphere ... If a body was made of tungsten or gold with a density of around 20 (compared to 3.3 for moon) then it could be very small and still hold an Earth type atmosphere ... I would guesstimate a planet/moon as dense as gold would only need to be about a few kms in diameter to have Earth Gravity and Earth atmosphere ...just a guess , but I do mean a few kms diameter!!

So when adding things to the moon density is an important consideration , Asteroids do have a slightly higher density than the moon , but what you are suggesting would be an impossible task , you would have to keep adding until it was about the size of Earth ...

GatheringKnowledge

That's not so ...From Search ... "Mars' mass is 6.42 x 1023 kilograms, about 10 times less than Earth
I didn't notice, that there's E23 in 6,39E23 kg for mass of mars, while it's E24 in 5,972E24 kg. Sorry... My mistake

oz93666

Woody

The main protector of our atmosphere is the Earths magnetic field, which diverts the solar wind around our atmosphere.
Observations of Mars show ancient features that point to it having a dense atmosphere in the (distant) past.
Measurements of the remnant magnetic field of Mars also indicate that it had a significant magnetic field in the (distant) past.
However being smaller than the Earth, Mars cooled quickly and its internal liquid core (where the magnetic field is generated) solidified,
so there is no longer a strong magnetic field to deflect the solar wind, which (over millennia) has continually stripped away the top layers of the atmosphere,
until now there is little left.
Titan is far enough out that the solar wind is not the force that it is in the inner solar system.

I don't think that gravity is the main limiter on the moon having an atmosphere,
If the moon had a magnetic shield, I think that it could hold a sensible atmosphere.

oz93666

I don't think that gravity is the main limiter on the moon having an atmosphere,
If the moon had a magnetic shield, I think that it could hold a sensible atmosphere.
It's all about the escape velocity at the surface of the moon ... this works the same for a rocket or a gas molecule ...

Speed of a gas molecule is dependent on temperature , and on the moon that's higher than escape velocity , so no atmosphere is possible.

Woody

Depends on the temperature,
I'm too lazy to work out the details, but Oz is probably correct,
because the "day" length on the moon is so long, it can get very hot at midday.

fligmin

The main protector of our atmosphere is the Earths magnetic field, which diverts the solar wind around our atmosphere.
Observations of Mars show ancient features that point to it having a dense atmosphere in the (distant) past.
Measurements of the remnant magnetic field of Mars also indicate that it had a significant magnetic field in the (distant) past.
However being smaller than the Earth, Mars cooled quickly and its internal liquid core (where the magnetic field is generated) solidified,
so there is no longer a strong magnetic field to deflect the solar wind, which (over millennia) has continually stripped away the top layers of the atmosphere,
until now there is little left.
Titan is far enough out that the solar wind is not the force that it is in the inner solar system.

I don't think that gravity is the main limiter on the moon having an atmosphere,
If the moon had a magnetic shield, I think that it could hold a sensible atmosphere.
I been wonder the same thing. Mass may not really be needed just an artificial Magnetic field some where down the road Using the sun for power and maybe a little extra mass. Maybe one day be possible, Not today.

fligmin

It's all about the escape velocity at the surface of the moon ... this works the same for a rocket or a gas molecule ...

Speed of a gas molecule is dependent on temperature , and on the moon that's higher than escape velocity , so no atmosphere is possible.
Maybe start by artificially adding heavier Gasses at first once you have a field in place. if that begins to hold you have something that helps start to distribute the heat and start a cool down. Might help here.

oz93666

I been wonder the same thing. Mass may not really be needed just an artificial Magnetic field some where down the road Using the sun for power and maybe a little extra mass. Maybe one day be possible, Not today.
Mass most definitely is needed , this is the minimum requirement I outlined ... the velocity of gas molecules must be below escape velocity for the moon/planet ....

Then if you have solar wind then you also need a magnetic field to stop the gas being "blown away" ... A magnetic field will have no direct effect on the gas , why would it ?? A magnetic field will in no way confine the gas to the moon/planet , it just diverts the solar wind.