A lake of water was found on Mars — and may be the first of many

'We think we have some evidence that there might be more.'

'We think we have some evidence that there might be more,' says research scientist Roberto Orosei

A view of the southern polar plain of Mars, with the Mars Express’s color-coded findings superimposed at the site where underground liquid water was detected. (USGS Astrogeology Science Center, Arizona State University, INAF)
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This past summer, Italian scientists stunned the science world when they announced they'd discovered a body of liquid water at the base of Mars's south polar ice cap. It was a hard-fought discovery made after 10 years of failed attempts with many emotional ups and downs.

How they looked for the underground lake

The discovery was made using the MARSIS radar instrument aboard the Mars Express orbiter. The radar penetrates the Martian surface and is reflected back to the spacecraft when it encounters liquid water.

Dr. Roberto Orosei, a research scientist at the Italian National Institute for Astrophysics, says the highly reflective radar signature they observed is a telltale sign of liquid water.

The publication of their findings was "a moment of immense relief" to Orosei.

"Seeing for the first time the data displayed on the screen showing, obviously, what we have been looking for, for years? Well, it's hard to describe that. It was really like getting rid of a big weight on your shoulders," he said.

The discovery of the liquid water lake was made using the MARSIS radar instrument aboard the Mars Express orbiter. (ESA - Illustration by Medialab)

Pitfalls, disappointments, and delays

Orosei's journey to the discovery was not an easy one. It started with a false positive detection that was actually carbon dioxide ice.

Later, they were getting puzzling and inconsistent results, which turned out to be due to the onboard MARSIS instrument only giving them partial information. They fixed that problem by taking over a memory chip on the spacecraft Mars Express to store the raw data before processing it.

Once those issues were resolved, the team was only able to get a few measurements before Mars's orbit took the spacecraft too far away from the areas of interest for another three years.

There are microorganisms on Earth that can survive in similar environments. And in fact, some of them can even use those salts for their metabolism.- Dr. Roberto Orosei , Italian National Institute for Astrophysics

After years of difficulties and false positives, the team suffered a significant human toll.

"Probably the lowest point was the fact that our principal investigator, our team leader, died after a long disease in 2015 — just months away from completing our data acquisition," added Orosei.

Where there's liquid water, could there be life?

The underground lake, at the base of Mars's south pole, is about 20 kilometres wide and at least one metre thick as that's the minimum that'd be required for the MARSIS instrument to even detect the lake.

According to Orosei, any liquid water that far underneath the planet's surface is probably very salty, since it would be totally frozen otherwise.

"Well certainly, it's not a place where one would go to vacation, but there are microorganisms on Earth that can survive in similar environments," he said. "And in fact, some of them can even use those salts for their metabolism."

The European Space Agency's Mars Express has used radar signals bounced through underground layers of ice to identify a lake of liquid water buried below the surface. (ESA/NASA/JPL/ASI/Univ. Rome)

Orosei says he and his team are continuing to look for more signs of water in elsewhere underneath the surface of Mars.

"We think we have some evidence that there might be more, but this is a bit early to draw conclusions."

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