14 DAY TRIAL // Curiosity has proven that all those Mars meteorites really are from Mars. It may sound strange for a rover that's currently on another planet to provide any data on rocks that have been on Earth for quite a while.
But that's just one of the benefits of having a well-equipped chemistry lab (which is what Curiosity is in essence) roaming around the Martian landscape.
One of Curiosity's two main chemical analysis instruments, the Sample Analysis on Mars (SAM), was able to provide data on a key characteristic of the Martian atmosphere, the ratio between two Argon isotopes.
Argon is commonly found as Argon-40, but also as the isotopes Argon-36 and Argon-38, in various proportions. Mars has a unique ratio, having lost most of its atmosphere by now. The lighter Argon-36 floated to the top and escaped more easily, leaving the heavier isotope more abundant than in other places in the solar system.
Scientists studying Martian meteorites have looked at the ratio between the two isotopes in pockets of gas trapped in the rocks. On average, they found a ratio of between 3.6 and 4.5 atoms of Argon-36 for every one Argon-38.
They assumed that the atmospheric ratio back on Mars was about four. Early studies by the Viking landers showed a ratio of between four and seven.
But Curiosity has finally provided a much more accurate number, 4.2. Throughout the rest of the solar system, on planets that haven't lost their atmospheres, the ratio is constant at 5.5.
With this new data, scientists will be able to much easier tell apart meteorites and prove which ones are from Mars and which aren't. This, in turn, will allow them to better put together a picture of Mars' past and its makeup. The results of the research were published in the Geophysical Research Letters journal.