We Found Water on Mars!


If you listen carefully, you can hear the sound of space nerds everywhere jumping up and down and shrieking with excitement. They know that scientists just announced new evidence for a giant lake on Mars!

Planetary scientists have known for some time that water flowed on Mars in the past, back when it had warmer temperatures and a thicker atmosphere. Right now Martian temperatures can reach -68 Celsius (-90 Fahrenheit), and any liquid water would have to be full of salt. Past searches have not found any bodies of water that were permanent or of this scale. But now, thanks to the Italian Space Agency’s use of the radar instrument, MARSIS, we have better evidence than ever that a giant, underground lake exists on Mars today!

Illustration of European Space Agency's Mars Express showing its MARSIS antenna. Credit: NASA/JPL/Corby Waste

“MARSIS was born to make this kind of discovery, and now it has,” said Roberto Orosei, a leading scientist on the investigation. The project uses radar technology to image below the surface of Mars, much like how we detect planes here on Earth. By sending out radio waves and measuring how they bounce back, scientists are able to form interpretations of what they cannot see.

By observing the materials the waves bounced off of and those they passed through scientists were able to dig through about three years’ of data from Mars’ south pole. The area is covered mostly in a thick layer of water ice, but the waves did something strange about two kilometers (one mile) below the surface. They formed a big, bright reflection on a surface – the interface between liquid water and ice.

Water detected under the south pole of Mars. Credit: ESA/NASA/JPL/ASI/Univ. Rome

The scientists wanted to check into other possibilities, like whether the layer could be frozen carbon dioxide. But liquid water was the case that made the most sense. The lake stretches across about 20 kilometers (12 miles). It is unclear whether it is a separate layer of water or liquid mixed with sediment. But that would still possibly be one of the most exciting sludges humans have ever found in space.

If there is water on Mars, that points to the huge – and even cooler possibility – of some form of alien life. Liquid water is critical for life as we know it. That is why searches for life and searches for water on other planets go hand in hand. Even this lake environment would be extremely harsh, bitterly cold, and filled with salts.

The chemicals in the lake could pose another problem. These salts are not the same as what you find in your salt shaker. These perchlorates are toxic to humans and more intense than bleach, and the Martian soil is full of them. So, if you ever do get the chance to visit an underground lake on Mars, be sure not to lick it!

Some especially tough and tiny creatures called extremophiles can technically live in these kinds of environments. They can go decades without water, survive in a vacuum, and even feed off of perchlorates. There is a chance that the water may be warmer and less salty than scientists think, but it would still be cutting it close even for extremophiles.

As hard as it may be to send a mission to Mars to look for life deep below the surface, knowing where to start the search is an amazing achievement in itself. And difficult is not the same as impossible.


extremophiles: microorganisms that thrive in conditions of extreme temperature or acidity

perchlorates: chemical compounds with extreme levels of salt

radar technology: uses radio waves to determine the distance, size, or speed of objects

radio waves: electromagnetic waves of frequency used for long-distance communication

sediment: matter that settles to the bottom of a liquid


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