Mars may have been the kind of place to raise the kids after all -- about four billion years ago.
Analysis of Martian meteorites and the rocks sampled by a Martian rover suggest striking differences -- differences that could be explained by the presence of atmospheric oxygen long before the Earth had it, reports Astrobiology Magazine.
An Oxford University research team, led by Professor Bernard Wood, examined data collected from surface rocks in the Red Planet's Gusev crater. Compared to meteorites, the rocks were five times richer in nickel, according to the team's study published in the science journal Nature.
"What we have shown is that both meteorites and surface volcanic rocks are consistent with similar origins in the deep interior of Mars but that the surface rocks come from a more oxygen-rich environment, probably caused by recycling of oxygen-rich materials into the interior," Wood noted.
"This result is surprising because while the meteorites are geologically 'young', around 180 million to 1400 million years old, the Spirit rover was analysing a very old part of Mars, more than 3700 million years old."
The reason for the differences? The Oxford team suggests a process called subduction took place -- essentially the rocks were oxidized long ago, then pulled slowly into the planet's shallow interior. That matter was later recycled to the Martian surface during volcanic eruptions.
Meteorites, on the other hand, came from Mars' deepest depths, remaining largely outside of this process.
The team's conclusion?
"Mars had an oxygen-rich atmosphere at a time, about 4000 million years ago, well before the rise of atmospheric oxygen on Earth around 2500 million years ago," Wood said.
"As oxidation is what gives Mars its distinctive colour it is likely that the 'red planet' was wet, warm and rusty billions of years before Earth's atmosphere became oxygen rich."
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