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Research Suggests Mars Once Had a Thick Atmosphere
astroengine writes "At one time, Mars had a thick, protective atmosphere — possibly even cushier than Earth's — but the bubble of gases mostly dissipated about 4 billion years ago and has never been replenished, new research shows. The findings come from NASA's Mars rover Curiosity, which has been moonlighting as an atmospheric probe as it scours planet's surface for habitats that could have supported ancient microbial life. 'On Earth, our magnetic field protects us, it shields us from the solar wind particles. Without Earth's magnetic field, we would have no atmosphere and there would be no life on this planet. Everything would be wiped out — especially when you go back 4 billion years. The solar wind was at least 100 times stronger then than it is today. It was a young sun with a very intense radiation,' Chris Webster, manager of the Planetary Sciences Instruments Office at NASA's Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News. Unfortunately for Mars, the last 4 billion years have not been kind."
Are we sure of that? While I can accept that Mars lost its atmosphere due to the solar wind stripping it, it should also be noted that Venus has a very weak magnetic field, yet it has a far larger atmosphere than the Earth. In fact, most of the magnetic field of Venus comes from the solar wind interacting with the atmosphere.
We need to put boots on Mars
Think of a planet like a giant centrifuge. Smash the two planets together and you'll create enough heat that you'd end up with a massive molten mass. Have the hit be 'off center' and you'll impart a huge amount of kinetic motion. Between gravity and centrifugal forces the heavier elements like iron will tend to end up towards the center while spinning, thus creating your magnetic field.
I don't read AC A human right
Assuming an Earth-sized planet in Venus orbit, even at its very closest, it would only accelerate the Earth at about 3 mm / s^2. If we can manage to move Mars and Mercury to collide with Venus in such a way that all material is maintained by Venus, such a minute effect on our orbit is meaningless. But since we're dreaming up unicorns, let's move Mars to be a moon of Venus instead. Then we can terraform both and have a nicely habitable double planet.