Re: How powerful a magnetic field is necessary to prot

Well, we are talking of two distinct forces/effects in this question. The 
first one is related to the gravity force, and escape velocity of a planet 
(in this case, Mars). The other one is the magnetic field, that can 
protect the planet surface and atmosphere from charged particles coming 
from the Sun.

Let's discuss some related topics about them.

If a new atmosphere could be created in Mars, maybe it could be preserved, 
because now the temperature is much lower than it was in the early times 
of the red planet. And temperature is the variable that acts against 
gravity in order to preserve or not the molecules in the atmosphere. 
Maybe, or maybe not, notice that we have to make the calculations to be 
sure. The temperature have changed, but the overall gravity remained 
constant since the formation of the planet.

The magnetic field can act as a shield that prevents the charged particles 
coming from the Sun to reach the surface and the atmosphere of the planet, 
depending upon its strength and configuration. As Mars today have a very 
small magnetic field [it may be passing by a reversal process], its 
surface is continuously bombarded by these particles, what causes the soil 
to be probably lifeless, even if there were adequated conditions to have 
life in the biological/chemical point of view.

To create a magnetic field strong enough to shield the planet, only the 
magnetization of the rocks could not be feasible. As the temperature 
increases (and going down increases the temperature in the terrestrial 
planets), you go beyond the Curie temperature of the mineral that form the 
rocks, and above this temperature, no material can preserve magnetization. 
Even if we could magnetize the entire crust, it would not be sufficient to 
create a magnetic field strong enough to make an effective shield.

So, the relationship you argued with is not valid in order of terraforming 
the planet. If you want to discuss these topics using these new 
informations, please feel free to contact the Mad Scientist Network with a 
new question.

Best regards, and a happy new year

Eder C. Molina
eder@iag.usp.br
Geophysicist
Dept. of Geophysics
Institute of Astronomy, Geophysics and Atmospheric Sciences
University of Sao Paulo - USP
Brazil