#AstroFriday: More Evidence for Water on Mars

NASA Hubble’s close-up view of Mars dust storm (Photo from NASA's Mars Exploration Image Gallery)NASA Hubble’s close-up view of Mars dust storm (Photo from NASA's Mars Exploration Image Gallery) Editor’s note: NASA announced that September 2017 to September 2018 is A Year of Education on Station for the International Space Station (ISS), featuring a variety of education-related events for students and teachers. Astronaut Richard (Ricky) Arnold, a volunteer board member for the Project WET Foundation, is the educator on board currently. Ricky discussed water on Mars in an #AstroFriday question-and-answer: Mars and Beyond. This post highlights new research about a possible lake of saltwater on Mars.

A new study indicates that a lake of liquid saltwater may exist beneath Mars’ southern polar ice. Researchers from the Italian Space Agency published the results of their study this week in the journal Science. If their results are confirmed, the lake would be the first body of liquid water ever detected on Mars—representing an important milestone in the ongoing research into whether life exists on the red planet. Research into “subglacial” lakes on Earth has shown that such bodies of water can contain microbial life.  

According to the journal Nature, lead study author and principal investigator Roberto Orosei and his colleagues found the lake using a radar instrument called Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) aboard the European Space Agency's Mars Express spacecraft, which launched in 2003:

“Orosei and his colleagues found the lake using a radar instrument called MARSIS aboard Mars Express, which launched in 2003. It sends radio waves bouncing off the surface and subsurface layers; the way in which the radar signal reflects back reveals the type of material that is present, such as rock, ice or water. The scientists focused their search on the layers of ice and dust that cover the planet’s south pole.

But the observations were frustratingly inconsistent. Mars Express sometimes saw a bright reflection in several locations, which did not reappear the next time the spacecraft flew over those sites. Finally, in 2012, the scientists decided to have MARSIS send back raw data, instead of performing automated processing before beaming the data to Earth. ‘This changed everything, and it was much more obvious to spot the bright reflectors,’ says Orosei.

The data showed bright reflections coming from a 20-kilometre-long zone in a region known as Planum Australe. After ruling out other possible explanations, such as carbon dioxide ice, the scientists concluded that the reflections were coming from subsurface water.”

The Nature article also notes that water appears across Mars today in various forms, left over from a time billions of years ago when the planet was warmer and wetter:

The surface of Mars (photo by NASA-JPL)The surface of Mars (photo by NASA-JPL) “Orbiting probes have spotted ice, including buried glaciers, in many locations. Spacecraft have photographed steep slopes whose appearance changes seasonally, as if liquid water is running downhill and leaving dark marks. And NASA’s Curiosity rover has measured water vapour in the planet’s atmosphere.”

While exciting, the new findings from the Italian Space Agency have not yet been confirmed by outside experts using other radar sounders. An article on CNN.com quoted Nathaniel Putzig, a senior scientist at the Planetary Science Institute, as saying: "We don't see the same reflector with SHARAD [the Shallow Radar sounder onboard the Mars Reconnaissance Orbiter], not even when we recently summed together [thousands] of observations to create CATSCAN-like 3-D views of both polar caps.”

"We're hoping to carry out that same imaging process with the MARSIS data next. I'm excited to see how the 3-D imaging will clarify the view of this detection and whether we will find similar ones elsewhere beneath the polar caps," he added.

If further studies do confirm that the lake exists, it could present new opportunities for research. According to Nature, “Researchers have drilled into subglacial lakes on Earth and sampled the water for signs of microbes, while others are developing technologies to reach a buried ocean on Jupiter’s moon Europa. There are no ice-drilling missions currently slated for Mars—but the latest discovery could change how scientists think about exploring the planet.”

As Jim Green, NASA’s chief scientist, concludes in the Nature article, “It begins a new line of inquiry that’s very exciting.”

To compare your water use to that of an astronaut, take the Water Use Challenge. Access this and other resources for teaching about water and space, including a lesson plan, at our Out of This World page.

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