NASA's Mars Curiosity rover confirms Martian meteorite origins

The latest data from NASA's Mars Curiosity rover will allow researchers to more accurately identify the origins of meteorites when they fall to Earth.

Scientists already refer to many meteorites as Martian meteorites, but they never had definitive proof of origin. The new measurement of argon gas in the red planet's atmosphere confirms their assessment.

The measurement showed that the ratio of argon-36 to argon-38 (two argon isotopes found throughout the solar system) is skewed heavier in Mars' atmosphere.

Earlier analysis of the suspected Martian meteorites revealed an argon ratio of 3.6-4.5 atoms of argon-36 to every one atom of argon-38. Curiosity's reading showed a ratio of 4.2 to 1.

"We really nailed it," said study lead-author Sushil Atreya of the University of Michigan, Ann Arbor, in a press release. A paper detailing the measurements was published Oct. 16 in the journal Geophysical Research Letters. "This direct reading from Mars settles the case with all Martian meteorites."

Beyond assisting scientists in determining the origin of Earth-bound meteorites, the argon ratio gives a better picture of how much of Mars' early atmosphere has been lost over the last several billion years. Knowing the severity of the loss will help them understand how the planet transformed from its earlier wet, warm climate to the current dry, cold, rocky world.

"Other isotopes measured by SAM (Sample Analysis at Mars) on Curiosity also support the loss of atmosphere, but none so directly as argon," said Atreya. "Argon is the clearest signature of atmospheric loss because it's chemically inert and does not interact or exchange with the Martian surface or the interior. This was a key measurement that we wanted to carry out on SAM."

Earlier Curiosity measurements have confirmed that there is no methane in Mars' atmosphere as well as evidence that water once flowed freely on the planet. In 2012, the rover discovered traces of carbon in the atmosphere.