[nudephil (OP)]

Greg sent us this question about terraforming Mars:

If you increase Mars's mass 38% by directing asteroids to it's surface, would it cause its core to once again generate a magnetic field to protect and further develop its atmosphere, as well as increase its gravity to the equivalent of earth? If so, would this not then be a better option than creating greenhouse gas machines on the surface which would only cover the atmosphere issue?

Is it theoretically possible?

[chris]

Why would you want to?

But to address the question, why 38%? Is there some special significance to that number?