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NASA's Maven Mission Solves the Mystery of Mars' Lost Atmosphere
StartsWithABang writes: If you came to the Solar System some 500 million years after its formation, you would've found two world with oceans of liquid water, continents and all the conditions we know of for life to begin thriving: Earth and Mars. But unlike our own world, Mars' organic history was cut short when it lost its atmosphere and became a barren, desert wasteland. While we had some pretty compelling theories as to how this happened, it was only with the advent of the Maven mission and its first science results that we discovered exactly how, how fast and when Mars lost its atmosphere. One cool discovery: aurorae appear diffuse and all over the entire night sky on Mars!
Mass too small, internal heat too low to generate a liquid iron core dynamo.
As TFA says though, we don't have to worry about that since if we put a good atmosphere on it by terraforming, it would last several million years.
meanwhile Venus without intrinsic magnetic field and closer to the sun has an atmosphere thicker than earth
The article says it would last for a while if we could, so...back of the envelope with probably horribly wrong numbers. Martian atmospheric density at the surface is 0.020 kg/m^3, human survival limit is something like 0.6 kg/m^3, so we need to add 29x current martian atmosphere to be long-term human survivable without a mask (for children and older, babies would still need higher pressure). NASA puts current atmospheric mass at 2.5e16kg, so we need to add 7.25e17kg. If we wanted to accomplish that task over a thousand years, or roughly 3.15e10 seconds, we would need to produce about 2.30e7kg of atmosphere every second for the duration. (At that speed, the loss rate of Mars's atmosphere due to solar wind is absolutely negligible.)
Martian surface area is 1.44e14m^2, which means we'd need to pull ~5,000 kg of atmosphere out of every single square meter of the planet if we don't have some other source. I don't know what density or composition Martian rock is, but rock in general is about 2.5g/cm^3, or 2500kg/m^3. So you might need to dig several meters into the ground to get what you're after, and expend one hell of a lot of energy to crack the oxygen out of it, but it's not like you'd need to dig a whole mile down across the whole planet or anything.