Mars Curiosity rover proves some meteorites on Earth are Martian
The rear of the stone from the Tissint Martian meteorite is almost completely covered with a glossy black fusion crust.
Some pieces of rock that fell to Earth from space are indeed from Mars, new measurements reveal.
Readings collected by NASA's Mars rover Curiosity have pinned down the exact ratio of two forms of the inert gas argon in the Martian atmosphere. These new measurements will not only help confirm the origins of some meteorites, they could also help researchers understand how and when Mars lost most of its atmosphere, transforming from a warm, wet planet to the red desert it is today.
By understanding exactly how much of the lighter isotope argon-36 is present in the Martian atmosphere and comparing it to the heavier isotope, argon-38, scientists were able to confirm what the composition of a Martian meteorite on Earth should be.
"We really nailed it," Sushil Atreya of the University of Michigan, lead author of a paper reporting the finding in Geophysical Research Letters, said in a statement. "This direct reading from Mars settles the case with all Martian meteorites."
Curiosity found that the ratio of argon-36 to argon-38 for Mars is 4.2 to 1. The lighter form of argon has escaped more readily than the heavier isotope, NASA officials wrote in a statement.
If Mars had not lost atmosphere through the course of its planetary history, its argon ratio would be 5.5 — the same as the sun and Jupiter, two cosmic bodies with so much gravity that isotopes cannot escape, NASA officials said.
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