One of the biggest challenges about flying to Mars is remembering why you went there in the first place. The Curiosity rover has been on the Red Planet for almost a year now, and the landing itself — an outrageous feat achieved by a stationary hovercraft that lowered the 1-ton Mars car to the surface by cables — was a global television event. But once the wheels touched the soil and all of the high fives had been exchanged, most people outside of the space community turned away. Curiosity, however, went to Mars to work, and if its sister rovers Spirit and Opportunity — both of which arrived in 2004 and one of which is still chugging — are any indication, it should be at it for a long time. In the past year, Curiosity has already made some intriguing discoveries about the mineralogy of Mars and the planet’s watery past, and this week it delivered again. In a pair of papers published in the journal Science, investigators announced new findings from the spacecraft about one of Mars’ most long-standing mysteries: how it lost its atmosphere, and why. (MORE: What It’s Like to Go to Mars) Mars’ modern atmosphere is only 1% the density of Earth‘s, but the planet’s watery phase is believed to have lasted for the first billion of its 4.5 billion years, which means its air must have been around that long too. But things were never likely to stay that way. Mars has only half Earth’s diameter, 11% its mass and 38% its gravity, making it easy for upper layers of the original atmosphere to have boiled away into the vacuum of space and been blasted out by meteor hits. And that cycle would build on itself: the thinner the air became, the easier it would be for space rocks to hit the ground, unleashing still more explosive energy and, in effect, blowing still more holes in the sky. But that’s only one mechanism. Planets can lose their air not just from the top up but … Continue reading Revealed: How Mars Lost Its Atmosphere