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Ancient volcanic eruptions on Mars may have deposited ice at the planet\u2019s equator<\/p>\n
RON MILLER\/SCIENCE PHOTO LIBRARY<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
The warmest parts of Mars host a strange, thick layer of ice beneath the surface, and we may have finally figured out how it got there. It might\u00a0have been shifted from the inside of the planet by extraordinary volcanic eruptions billions of years ago \u2013 and all that water could be crucial for future crewed missions.<\/p>\n
We\u2019ve long known that Mars is rich in ice, but most of it seemed to be in the ice caps that top both of the poles. Over the past several years, though, radar evidence from orbiters around the Red Planet has mounted, indicating there is also ice in its equatorial regions. \u201cThere\u2019s this frozen layer at the equator \u2013 that\u2019s odd because it\u2019s the hottest part of the planet,\u201d says Saira Hamid at Arizona State University.\u00a0At midday near the equator, it can reach about 20\u00b0C (68\u00b0F).<\/p>\n
Hamid and her colleagues ran a series of simulations of volcanic eruptions on Mars and found that over the course of millions of years, a series of explosive eruptions could have blasted water from the interior up into the atmosphere \u2013 back when Mars had a far denser one, billions of years ago. There, it would freeze and snow down to form the ice layers we see now. \u201cIt\u2019s truly a story of fire and ice,\u201d says Hamid.<\/p>\n
<\/p>\n These eruptions would have been, in some ways, unlike anything we see on Earth. Mars\u2019s lower gravity means that plumes of volcanic dust, water and sulphur could have reached a height of 65 kilometres above the ground \u2013 or potentially all the way to space, depending on how thick the atmosphere was when the eruptions occurred.<\/p>\n Once the material snowed back down, the water would compact into dirty ice, covered in an insulating sheet of volcanic ash. This dust would keep the ice from sublimating away into space, helping to preserve it up until the present day.<\/p>\n \u201cThe whole possibility of this type of an ice-rich deposit has been a bit of a head-scratcher for a lot of people,\u201d says Tom Watters at the Smithsonian Institution in Washington DC. Particularly confusing is one of the largest volcanic formations near Mars\u2019s equator, called the Medusa Fossae Formation, mostly because of its sheer size: \u201cIf you melted all the water that we think we see in the Medusa Fossae formation, you would fill the Great Lakes. It\u2019s a lot of water.\u201d<\/p>\n Another possible explanation that researchers had cooked up for all that ice is that Mars\u2019s obliquity \u2013 its tilt with respect to the sun \u2013 may have changed dramatically over the course of its history, so the equatorial regions may have once been the poles. \u201cBut with these volcanic eruptions, you don\u2019t need to transport the ice from other areas of the planet, you don\u2019t need changes in obliquity,\u201d says Hamid. \u201cIt\u2019s just simpler.\u201d<\/p>\n The equatorial region is also the best place for missions to Mars to land, because the\u00a0paltry atmosphere is thickest there, which helps slow down landers on their approach to the ground. A source of water there could be incredibly useful for eventual human missions\u00a0\u2013 perhaps not the very first ones, but later landings could take advantage of the ice.<\/p>\n \u201cThose initial trips, you want to bring enough water in case we\u2019re completely wrong and there\u2019s some bizarre material that we\u2019re seeing in the radar,\u201d says Watters. \u201cI wouldn\u2019t go without enough water and just bring a shovel and assume you\u2019re going to hit water. Bring a shovel, but bring enough water, too.\u201d<\/p>\n Topics:<\/p>\n<\/section><\/div>\n