The Rare Metals on Mars Came From a Giant Collision

Saturday, 17 March 2018 - 4:35PM
Space
Mars
Saturday, 17 March 2018 - 4:35PM
The Rare Metals on Mars Came From a Giant Collision
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NASA/JPL-Caltech/MSSS
For some reason, Mars has a lot of metals that shouldn't be there. 

Specifically, there's a lot more "iron loving" elements like gold, platinum and iridium than there should be inside the Red Planet's mantle, when those elements should be closer to the planet's core. Since there aren't any viable scientific models that show these forming naturally, a new study published in Geophysical Research Letters proposes another idea: that a massive body colliding with Mars could have deposited all these metals.

Their model is based on the idea that the same event happened to Earth a long time ago, when a lunar-sized body crashed into our planet (which may or may not have been what formed the Moon) and deposited a similar amount of rare metals into the Earth's mantle. A model that includes a colossal impact like that would explain the metals found inside the Earth, and a similar model also explains why Mars' mantle is so heavy with these metals.



The study predicts that this Mars collision likely happened around 4.5-4.4 billion years ago, and would have been absolutely catastrophic if there was any life there at the time. According to Ramon Brasser, a co-author of the study and a planetary scientist at the Tokyo Institute of Technology, who said the following to Astrobiology Magazine:

Opening quote
"High pressure experiments indicate that these metals should not be in the mantle. These metals don't like being dissolved in silicate and instead they prefer to sink through the mantle into the Earth's core. The fact that we do have them at all means that they must have arrived after the core and the mantle separated, when it became much more difficult for these metals to reach the core."
Closing quote


On top of that, this would also explain why Mars has such different northern and southern hemispheres. The planet's southern half is old and cratered, while the northern half seems to have a newer surface with lots of volcanic activity, a contrast which could have been created by something huge smashing into one hemisphere.

There's no way to claim whether this body was one of Mars' two moons, Phobos or Deimos, but it's possible. Neither moon has taken credit for it, if so.
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