Earth’s most eminent emissary to Mars has just proven that those rare Martian visitors that sometimes drop in on Earth — a.k.a. Martian meteorites — really are from the Red Planet.
A key new measurement of Mars’ atmosphere by NASA’s Curiosity rover provides the most definitive evidence yet of the origins of Mars meteorites while at the same time providing a way to rule out Martian origins of other meteorites.
Scientists identified meteorites, such as this one nicknamed “Black Beauty,” as Martian in origin. The new measurement is a high-precision count of two forms of argon gas—Argon-36 and Argon-38–accomplished by the Sample Analysis at Mars (SAM) instrument on Curiosity. These lighter and heavier forms, or isotopes, of argon exist naturally throughout the solar system. But on Mars the ratio of light to heavy argon is skewed because a lot of that planet’s original atmosphere was lost to space, with the lighter form of argon being taken away more readily because it rises to the top of the atmosphere more easily and requires less energy to escape. That’s left the Martian atmosphere relatively enriched in the heavier Argon-38.
Years of past analyses by Earth-bound scientists...