The news from Mars

Dust storms, organic chemistry and liquid water on the Red Planet.

It’s been a big few months for Mars watchers. First, in late June, a small dust storm grew and grew, combining with other storms until it finally kicked up a dust cloud so big it enveloped almost the entire planet.

Dust storms the size of continents are common on Mars, but global dust storms only occur roughly once every three years (that’s once every five or six Earth years), usually during summer in the Red Planet’s southern hemisphere. The storms are self-limiting, as the dusty haze blocks the sunlight that delivers the heat to power them. In this case, by late July, a month or so after it began, the dust was slowly settling back to the ground.

The sun-blocking tempest was good news for storm-watchers but bad news for NASA’S solar-powered ‘Opportunity’ rover, which has yet to resume operations.

Second, three discoveries boosted the prospects of past and present life on Mars. The ‘Curiosity’ rover (it’s nuclear-powered so it survived the dust storm) detected deposits of organic molecules in 3.5 billion year old rock samples. Back in 2014, Curiosity’s on-board lab identified organic molecules in the mudstone of Gale crater, an ancient lakebed. This June, Curiosity’s instruments detected deposits 100 times richer in samples drilled from the slopes of 5 km high Mt Sharp which sits in the centre of Gale crater. After baking the samples to release the molecules, it detected a rich array of organic compounds such as thiophene, benzene and propane. Coal or shale samples on Earth, baked the same way, release similar molecules.

The next thrill was that Curiosity detected levels of methane rising over the summer – 2.5 fold higher than in winter. It could mean the gas is being vented from thawing organic materials, as happens on Earth. Nevertheless while Earth’s methane is mostly of biological origin, Martian methane could just as easily be produced by non-biological means. Both of Curiosity’s discoveries were reported in Science in June.

Perhaps the most dramatic boost to the search for Martian life came in late July, when another Science paper reported a lake lying 1.5 km beneath the southern polar ice cap. Discovered using the radar probe on the European Space Agency’s Mars Express satellite, the lake is some 20 km wide and at least a metre deep. While the water would undoubtedly be cold and salty, the lake is perhaps the least inhospitable location for life on Mars.

But lest we get out hopes up too high, it turns out we are unlikely to be able to terraform Mars. One proposal is that by releasing frozen CO locked in the polar icecaps, the greenhouse gas might both warm the planet and provide for plant growth. Alas, a report in Nature Astronomy finds there’s just not enough CO .