Italian astronomers have detected a shallow body of liquid water beneath the planet’s South Polar ice cap
by Philip Ball / July 25, 2018 / Leave a comment
A buried lake at the South Pole on Mars. The blue area is thought to be a lake of liquid water below the surface. Photo: US Geological Survey Astrogeology Science Center, Arizona State University/National Institute for Astrophysics (INAF), Bologna
Anyone expecting the moon’s Sea of Tranquility to live up to its name will have been disappointed with the expanse of dry, barren rock revealed when Apollo 11 landed there 49 years ago. The naming of this expanse of lunar territory by the Italian Jesuit astronomer Giovanni Battista Riccioli in 1651 acknowledged Galileo’s contention that the moon is a world topographically like ours, although Ricciolo thought it was uninhabited.
Likewise the dark streaks of “canali,” or channels, described in 1877 on Mars by another Italian astronomer, Giovanni Schiaparelli. Although excitedly translated as “canals” and thereby helping to inspire HG Wells’ The War of the Worlds, these proved bone dry. Such linguistic slippage attests to our long-standing impulse to imagine water on other worlds.
But the martian lake just discovered from radar soundings—taken by the European Space Agency’s Mars Express spacecraft in orbit around the planet—is no mirage or euphemism. It appears indeed to be a shallow body of liquid water about 20 km wide, close to the martian South Pole.
That there seems to be a reservoir of water (and not just ice) on the planet surely ranks as one of the most astonishing finds on Mars for a long time. It seems only fitting that Italian astronomers, led by Roberto Orosei of the National Institute of Astronomy in Bologna, are once again behind the discovery.
There seems no doubt that Mars once hosted a great deal of water: rivers and even shallow oceans. Billions of years ago it is thought to have had a warmer climate and a thicker atmosphere, so that much of the water now frozen along with carbon dioxide (aka “dry ice”) in the polar caps was liquid. Evidence of that remains, most strikingly in the sinuous canyons carved out of the rocky martian surface, which can hardly be anything but the work of water erosion. There is also a record of Mars’ watery past in its rocks, some of which have a chemical composition that testifies to their having been formed in water. Gale Crater, just south of the martian equator and formed by a meteorite impact around 3.5-3.8bn…
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