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Mars’ atmosphere is draining into space

The already-thin Martian atmosphere is getting thinner, according to the NASA team in charge of the Mars rover Curiosity. In two papers that appeared in this week’s issue of the journal Science, team researchers reported that the air on the red planet has been slowly but steadily dissipating into space over the last 4 billion years.

Curiosity, which has been roaming the Martian surface since its landing there in August 2012, has been analyzing the chemical compounds of scores of soil and rock samples. But it’s also been measuring the gases within the Martian air and gases emanating from solid fixtures along the ground.

The rover’s instruments test the gases to calculate the ratios of various isotopes—atoms that are like those of known elements but have different numbers of neutrons and are therefore heavier or lighter. In our atmosphere, there are far more light isotopes than heavy ones, and this is normal for a terrestrial planet.

If the ratio of heavy atoms increases, it means that the atmosphere is draining away. Light isotopes can escape a planet’s gravity more quickly, so they are always the first to go.

And Curiosity’s human team found that the air on Mars exhibits a significantly higher presence of heavy isotopes. The rover’s tests indicated, for instance, that Mars’ air holds five times as high a concentration of deuterium, an isotope of hydrogen, than Earth’s air does.

Chris Webster, the lead investigator for the tunable laser spectrometer, one of the rover’s instruments, told ABC News that many researchers suspect that an object the size of Pluto may have crashed into Mars around 4.5 billion years ago and threw off the planet’s magnetic field, a consequence of which was the sudden release of much of the atmosphere into space.

NASA researchers want to collect more atmosphere measurements from other areas of the planet and throughout the Martian year, which is almost twice as long as a year on Earth. That might be a job better suited for a satellite, however, according to Paul Mahaffy, a NASA scientists and lead author of one of the Science papers.

One such satellite will soon be on its way. NASA is planning to launch the Mars Atmospheric and Volatile Evolution (MAVEN) spacecraft this November with a mission to circle Mars and assess its atmosphere and the rate of atmosphere loss in-depth. MAVEN will be the first-ever space satellite to do so, once it reaches Mars at some point in late 2014.