Friday, December 25, 2020

Subsurface lakes raise new questions about life on Mars

Posted By on Fri, Dec 25, 2020 at 3:30 PM

Arizona in Focus is a podcast from Cronkite News, the news division of Arizona PBS. This season we are focusing on science and technology stories that explore everything from driverless cars to innovating a vaccine during the pandemic.

PHOENIX – Planetary scientists have confirmed the existence of a large saltwater lake under the icy surface of Mars, and they discovered three more lakes beneath the red planet’s south pole.

The discovery, which was published in the journal Nature Astronomy in September, is based on radar data obtained from the European Space Agency’s Mars Express spacecraft.

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“Mars actually has a lot of water in a lot of different places and a lot of different forms,” said Jonathon Hill, a mission planner at Arizona State University’s Mars Space Flight Facility. “But none of them are in forms that would even potentially, you know, provide for current life somewhere. This (new research) I think, has the potential to be different.”

In 2018, the spacecraft’s Mars Advanced Radar for Subsurface and Ionosphere Sounding detected an underground lake of water about 4,921 feet below the ice, according to the European Space Agency’s website. The three new lakes vary in size, but the largest is 65,616 feet by 98,425 feet. Scientists say the lakes likely have a high salt content to remain liquid in temperatures as low as minus 225 degrees Fahrenheit.

Mars used to be “warmer and wetter with water flowing across the surface, much like early Earth,” the European Space Agency said.

“While it is not possible for water to remain stable on the surface today, the new result opens the possibility that an entire system of ancient lakes might exist underground, perhaps millions or even billions of years old,” it said. “They would be ideal locations to search for evidence of life on Mars, albeit very difficult to reach.”

Astronomer Jennifer Hanley at Lowell Observatory in Flagstaff studies liquid stability throughout the Solar system including on Mars, Saturn’s moon Titan and Jupiter’s moon Europa. She said to understand lakes on Mars, people should think about how salt reacts on roadways to clear snow and ice.

“You can actually see it form little liquid droplets,” she said. “But that’s the key. It’s droplets, right? There’s not a lot of actual liquid there.”

Researchers believe something similar happens on Mars. With an average high of minus 80 degrees Fahrenheit, any liquid is probably quite salty.

Mike Sori, an assistant professor in the Earth, Atmospheric and Planetary Sciences Department at Purdue University in Indiana, said the polar ice caps of Mars are about 621 miles in diameter. He describes the liquid water as “slush or sludge” and believes it is localized on the planet. Even though this water exists, Sori said there is a slim chance life is present on Mars.

“So it wouldn’t be a lake that has existed for billions of years that, you know, potentially has life on it,” he said. “We think it would be really just a sort of transient phenomenon.”

Future missions to Mars may reveal some answers. In July, NASA launched the Perseverance Rover, which is on its way to the red planet and is expected to land in February. Hill said he hopes this rover, which is the size of a Hummer vehicle, will land in an ancient lake bed.

“Its specific goal is to not just find good samples, but to pick them up, cache them and leave them behind for the next mission to bring back to Earth,” Hill said.

Another hope is to have rock and soil samples in researchers’ hands in the near future. Those samples, scientists hope, eventually will help unlock the secrets of the red planet.

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