# Planet Mechanics Question

1. Feb 8, 2014

### JeremyPeel

Please forgive me. My education is lacking go easy on me.

The radius of 6378.1 km has enough gravity to hold this atmosphere in place and has a magnetic field strong enough to protect it.
1. My question is would mars have the same atmosphere and magnetic field if it were the same radius ((+/- 10% of earth)(not sure how to prove this out)) and had the same radius core ((+/- 10% of earth)(not sure how to prove this out))?
2. Would all bodies with this radius and mass ((+/- 10% of earth)(not sure how to prove this out)) and with enough energy from the parent star have life as we know it?

I think that would imply that the radius of earth is in direct correlation to life as we know it.
Please let me know if these idea are sound!

2. Feb 8, 2014

### davenn

Hi Jeremy
welcome to PF

some possibilities there :)

as far as the magnetic field goes, do you understand how the earth's magnetic field originates ?

also google the Goldilocks Zone to find out about the possibility of planets supporting life as we know it

cheers
Dave

3. Feb 8, 2014

### JeremyPeel

Love the anti-gravity quote btw. Maybe i'm asking the wrong question. Wouldn't gravity prohibit life from any planet with the radius 30 % larger or smaller than earth, regardless of distance from the sun in respect to how gravity holds onto the atmosphere of the planet and all that implies?

4. Feb 8, 2014

### JeremyPeel

I think i understand the magnetic field with the solid iron core and molten iron around that. A big electro-magnet the currents flowing in the churning molten iron correct?
How small would the core have to be to not protect the earth from the solar winds?

5. Feb 8, 2014

### JeremyPeel

Thanks for all your help. I looked at the links and it was a lot of help.

6. Feb 19, 2014

### seany

If mars had has the similar solid rock content with similar radioactive element amount as earth, that would keep the matle liquid, and that would make a similar magnetic field. I am ignoring local magnetic anomalies generated by solar wind on a planet without significant atmospher, like moon (okey, planetoid)

mass alone does not define atmospheric stability, it has to lack lighter contents, e.g. H, He, and the heavier contents like earth has to previal for a stable atmosphere. I am also ignoring incoming solar radiation is different in two planets. The incoming solar radiation drives the heating and escape (and some other escape processes) in the atmosphere.