Since the Curiosity rover landed on Mars last August, it has been sniffing the air for clues to Mars past. In addition to the abundant Carbon Dioxide and small amounts of nitrogen gas that scientists expected to find, a surprising amount of argon was found as well.
Argon is a good indicator of atmospheric history because of its stability. The amount of argon isotopes detected is helping scientists unravel questions about how Mars lost much of its atmosphere.
These measurements come from Curiosity's Sample Analysis at Mars (SAM) instrument. SAM is made up of a mass spectrometer, gas chromatograph, and laser spectrometer which work together to measures within and accuracy of 10 parts per thousand. SAM has revealed that Martian air has lot more of the heavier argon-38 isotope than lighter argon-36.
Where this gets interesting is when atmospheric readings from Curiosity today are compared readings from the 1970s Viking missions and from a few billion years ago.
But where can you find ancient Martian air samples? Turns out there is one at the North Carolina Museum of Natural Sciences, visitors can even touch it. Scientists have been measuring gas trapped inside Martian meteorites like the one on display the museum for many years.
Research published this week by the journal Geophysical Research Letters points to a loss of argon "perhaps as high as 85-95% from the atmosphere of Mars in the past 4 billion years."
This clearer picture of Mars atmospheric history will help scientists better understand how Mars transformed from warmer, wetter world to the cold, drier place it is today. For the record, Monday's high at Gale Crater was -11F.