Mars may have lost much of its original atmosphere, but the remaining atmosphere on the Red planet is still quite active, findings from NASA's Curiosity rover indicate.
Evidence has strengthened this that Mars lost much of its original atmosphere by a process of gas escaping from the top of the atmosphere, NASA's Jet Propulsion Laboratory, California, said in a statement.
Curiosity's Sample Analysis at Mars (SAM) instrument analysed an atmosphere sample last week using a process that concentrates selected gases. The results provided the most precise measurements ever made of isotopes of argon in the Martian atmosphere.
"We found arguably the clearest and most robust signature of atmospheric loss on Mars," said Sushil Atreya, a SAM co-investigator at the University of Michigan, Ann Arbor.
SAM found that the Martian atmosphere has about four times as much of a lighter stable isotope (argon-36) compared to a heavier one (argon-38).
This removes previous uncertainty about the ratio in the Martian atmosphere from 1976 measurements from NASA's Viking project and from small volumes of argon extracted from Martian meteorites.
The ratio is much lower than the solar system's original ratio, as estimated from argon-isotope measurements of the Sun and Jupiter. This points to a process at Mars that favoured preferential loss of the lighter isotope over the heavier one.
While daily air temperature has climbed steadily since the measurements began eight months ago and is not strongly tied to the rover's location, humidity has differed significantly at different places along the rover's route. These are the first systematic measurements of humidity on Mars.
Trails of dust devils have not been seen inside Gale Crater, but Rover Environmental Monitoring Station (REMS) sensors detected many whirlwind patterns during the first hundred Martian days of the mission, though not as many as detected in the same length of time by earlier missions.
"A whirlwind is a very quick event that happens in a few seconds and should be verified by a combination of pressure, temperature and wind oscillations and, in some cases, a decrease is ultraviolet radiation," said REMS Principal Investigator Javier Gomez-Elvira of the Centro de Astrobiologia, Madrid.
