Curiosity Rover Provides New Measurement for Confirming Origins of Martian Meteorites

NASA's Mars rover Curiosity has provided a key new measurement of the Red Planet's atmosphere that, scientists say, can be used to determine whether or not meteorites are Martian.

Taken by the rover's Sample Analysis at Mars (SAM), the measurement is a high-precision count of two forms of argon gas: Argon-36 and Argon-88.

While both exist throughout the solar system, the ratio between the two is skewed on Mars since the planet has long since sloughed off much of its original atmosphere off into space, leaving a larger proportion of the heavier isotope, Argon-38, as its lighter peer requires less energy to escape.

Previous studies of gas bubbles in Martian meteorites had placed the ratio between 3.6 and 4.5 -- or 3.6 to 4.5 atoms of Argon-36 to every atom of Argon-38. In the 1970s, NASA's Viking landers pinned the ratio range between four and seven. The newest and most accurate measurement suggests the correct ratio is 4.2.

"We really nailed it," said Sushil Atreya of the University of Michigan, the lead author of the paper regarding the findings. "This direct reading from Mars settles the case with all Martian meteorites."

Argon is especially interesting to researchers because it is a noble gas, meaning it does not react with other elements or compounds.

"Other isotopes measured by SAM on Curiosity also support the loss of atmosphere, but none so directly as argon," Atreya said. "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."

The study was published in the journal Geophysical Research Letters.