The atmosphere on Mars was once thicker, warmer and wetter than it is today until it was damaged in a ‘catastrophic collision’ with a planet the size of Pluto, scientists claim. Data collected by Nasa’s Curiosity rover suggests the Red Planet’s atmosphere once had more oxygen in it than Earth, giving serious weight to the theory it could have previously harboured alien life. Yet a major upheaval, thought to have been caused when a Pluto-sized planet collided into Mars billions of years ago, created a shift in gases that led to the atmosphere around it to shrink. A team of Nasa scientists claim that a change in the ratio of two different kinds of argon gas is evidence that the atmosphere has been stripped away. Nasa’s Dr Chris Webster said: ‘As Mars became a planet and its magma ocean solidified, catastrophic outgassing occurred while volatiles were delivered by impact of comets and other smaller bodies.
‘Solar wind, and the possible impact by a Pluto-sized body is thought to have stripped much of the initial early atmosphere from the planet, and since then the atmosphere has developed as a balance between volcanic injection and loss to space.’ The Nasa scientists were investigating the atmosphere after one of their telescopes on Earth had detected a surprising and mysterious amount of methane in three regions in the Martian western hemisphere. This presence of methane could have suggested there was some form of life living on the planet. Yet the Curiosity rover did not find any methane, which has disappointed those who believe microbes may still linger there.
On Earth, methane is mainly a by-product of life – from animal digestion and decaying plants – and the gas can also be produced by non-biological processes. But last year, the Curiosity team reported no definitive whiff of methane near the landing site, and since then, the rover has taken several more air samples. There are also plans to sniff the atmosphere during a drive to the Mount Sharp mountain. And in the autumn NASA is set to launch a Mars-orbiting spacecraft aimed at solving the methane mystery. Called Maven, the craft will target the Martian atmosphere. Scientists want to know if it actually exists, determine the abundance and whether that varies by year or location. ‘The fact that it’s turned out to be pretty much disproven – it’s not a surprise, but a disappointment perhaps,’ planetary scientist Adrian Brown of the SETI Institute in California, told Wired magazine. The Curiosity found the air is made mostly of carbon dioxide. This closely matched what the twin Viking landers detected in the late 1970s and what scientists have gleaned from Martian meteorites. And there was also interest in what may have existed in the past on Mars, after Curiosity found that much of the planet’s atmosphere has been lost over time, suggesting it was once warmer.
This would have been more conducive to liquid water flowing on the surface – and potentially even life existing on the planet, reported Wired. Mars’ atmosphere is overwhelmingly dominated by carbon dioxide, unlike Earth’s air, which is a mix of nitrogen and oxygen. However, there was still a small surprise. Viking found nitrogen to be the second most abundant gas in the Martian air, but Curiosity’s measurements revealed a nearly equal abundance of nitrogen and argon, a stable noble gas.
Mission scientists are puzzled, but suspect it might have to do with the different tools used to sample the atmosphere. ‘It’s more or less an interesting observation’ but doesn’t change the notion that Mars lost most of its original atmosphere to space, transforming the planet into a cold desert, said Paul Mahaffy of NASA’s Goddard Space Flight Center, who is in charge of Curiosity’s air sampling experiments. The nuclear-powered, six-wheel rover set down in an ancient crater near the Martian equator almost a year ago. The measurements were detailed in two studies appearing in the journal Science.
