Liquid water finally discovered on Mars

By Marina Wang

For the first time, radar measurements taken from the Mars Express Orbiter have provided astronomers with convincing evidence of liquid water on Mars. The newly detected reservoir is around 12 miles wide, located near Mars’s South Pole and buried under a thick layer of ice.

Locating liquid water on Mars is key to detecting extra-terrestrial life on the planet. Previously, the most compelling evidence of liquid water was in the form of dark streaks running down the planet’s hills and gullies. However, that evidence has been contested, with some astronomers positing that the streaks were caused by tumbling debris and not water.

Astronomers made this recent discovery by analysing three years’ worth of data from an instrument called Marsis which uses low-frequency radar aboard the Mars Express spacecraft.

The reservoir’s depth is unknown, but the temperature is estimated to be around -68 C, and although very cold, remains liquid because of the high amount of salts dissolved in it. However, these salts may make sustaining microbial life difficult.

“High salt conditions are good for maintaining a liquid state but are a challenge for life,” said Mark Sephton, an astrobiologist at Imperial College London to The Guardian. “If the salt concentrations outside of the cell are higher than the inside then it draws water out from inside the cell and the cell shrinks and desiccates. Life can adapt by synthesising organic molecules to stop the process but there are limits, beyond which the high salinities in the cell interfere with biochemistry and the cell dies.”

Testing the water for signs of life may also take a while—astronomers would have to design a device that could drill through the thick ice sheet—technology that doesn’t exist yet. In the meantime, researchers will continue looking for liquid water on other areas of the planet.