A new map of Mars shows where it was once covered in water

A map of hydrated mineral deposits on Mars.  Green represents hydrated sulfates;  red is hydrated clays;  orange is carbonate salts;  and blue is hydrated silica and aluminosilicate clays.

A map of hydrated mineral deposits on Mars. Green represents hydrated sulfates; red is hydrated clays; orange is carbonate salts; and blue is hydrated silica and aluminosilicate clays.

The history of water on Mars is much deeper than scientists believed. A new project has mapped hundreds of thousands of rock formations on the Red Planet that may have been altered by large amounts of water in the past.

Data from two Mars orbiters has been used to create a detailed global map of mineral deposits on Mars, showing where water may have once flowed on the planet. “I think we’ve collectively oversimplified Mars,” said planetary scientist John Carter of the Institut d’Astrophysique Spatiale de Paris, and lead author of a paper published in the journal Icarus, said in a statement.

Observations from the European Space Agency Mars-Express orbiter and NASA Mars reconnaissance orbiter enabled the researchers to create the map, a project that spanned a decade, according to ESA. Prior to this work, scientists only knew about 1,000 rock formations on Mars that contained hydrated minerals. But the new map reveals hundreds of thousands of such outcrops. “This work has now established that when you study ancient terrains in detail, not seeing these minerals is actually an oddity,” Carter said.

This image shows hydrated minerals at Jezero Crater (larger red and orange area in upper left) and Gale Crater (smaller green circle in middle right).  Both craters were explored by robotic rovers.

This image shows hydrated minerals at Jezero Crater (larger red and orange area in upper left) and Gale Crater (smaller green circle in middle right). Both craters were explored by robotic rovers.
Image: ESA/Mars Express (OMEGA) and NASA/Mars Reconnaissance Orbiter (CRISM)

Mars is a dry planet today, but various evidence suggests there was once water flowing through it its area. Aqueous minerals can be found in rocks that have been chemically altered by water in the past and have generally turned into clays and salts. When small amounts of water interact with the rocks, they remain relatively unchanged and retain the same minerals found in the original volcanic rocks. But if large amounts of water interact with the rocks, the soluble elements are dissolved by the water, leaving behind more aluminum-rich clays.

The new findings suggest that water played a much larger role in shaping Mars’ geology throughout its history. However, it remains unclear whether the presence of water was constant over time or whether there was an ebb and flow of water on Mars over shorter periods early in its history. “The evolution from lots of water to no water isn’t as clear as we thought, the water didn’t stop overnight,” Carter said. “We see a great diversity of geologic settings, so no single process or timeline can explain the evolution of Mars’ mineralogy.”

Although the map doesn’t provide all the answers, it does point to places where more clues can be found. The areas identified here will be excellent candidate landing sites for future missions to Mars; some of them may even still have water ice buried below the surface.

After: Mars is hiding its ‘lost’ water beneath the surface, new research suggests

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