Before going incommunicado behind the Sun for a month,
The findings, announced by
Curiosity's Sample Analysis at Mars instrument sniffed the Martian atmosphere and counted up the isotopes of argon in the air. Isotopes are heavier and lighter versions of the same element, and when a planet starts to lose its atmosphere, the lighter isotopes in the upper layers are the first to go. So if scientists see fewer of the lighter isotopes than expected, it might mean that there was once much more air there.
The researchers looked at two isotopes of argon: the heavier argon-38 and the lighter argon-36. They found that there was four times as much argon-36 as argon-38 -- a lower share of the lighter argon than expected based on data from other parts of the solar system.
Some of that missing argon-36 must have escaped because the top of the atmosphere had started to blow away, they surmised. This could mean Mars' atmosphere was much thicker in the past than what Curiosity picks up today.
Curiosity is experiencing what scientists call "solar conjunction," when the sun comes between Earth and Mars, blocking communications until May. But Curiosity isn't taking a vacation. The rover has to take weather and radiation measurements every day — part of a detailed list of chores sent by the Mars Science Laboratory team at JPL.