Mars May Have Been Habitable for a Long, Long Time
published during a waxing crescent moon.
05/31/2017

The Curiosity Rover has made some remarkable discoveries in its attempt to determine whether the Red Planet could have ever supported microbial life. Now, it’s made another. In addition to discovering that Mars has dried streambeds, as well as carbon, nitrogen, oxygen, and other life-sustaining elements, samples gathered by Curiosity indicate that the timeline for the planet’s potential habitability is much longer than scientists previously thought.

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Halos. Credit: NASA/Caltech

Ever since it landed on Mars, the intrepid rover has moved toward the 96-mile-wide, 3.5-3.8-billion-year-old Gale crater. The crater boasts an 18,000-foot-high peak, Mount Sharp, which Curiosity is currently climbing. Mountains and craters are scientists’ version of time machines—studying layers of sentiment can provide information about a place’s geological eras and features. NASA made the crater Curiosity’s destination because it seemed like the best place to gauge whether the planet ever could have supported life.

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Gale Crater. Credit: NASA

As described in a  new report published in Geophysical Research Letters, scientists saw “halos” in the crater—circular areas of rock that are lighter in color than the surrounding rock. When samples from those halos were tested, researchers found unusually high levels of silica, which they believe was left behind by water.

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Mount Sharp. Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

The crucial discovery here was finding silica in both the older, foundational bedrock, as well as the younger rocks on top of it. Lead author and scientist at the University of Copenhagen and Los Alamos National Laboratory, Jens Frydenvang, says the silica “appears to have migrated” from the old rocks to the younger ones, which indicates that “even when the lake eventually evaporated, substantial amounts of groundwater were present for much longer than we previously thought.” They also found rocks with high silica concentrations that they believe were moved by the wind after the lake evaporated, suggesting that the existence of groundwater long after the lake became a crater.

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Gale Crater. Credit: NASA/JPL-Caltech/University of Arizona

The presence of groundwater doesn’t necessarily equate to habitability, but it’s a necessary piece. Couple that with Curiosity’s previous discovery of Boron on Mars and the likelihood of habitability increases.  While scientists have known for a while that Mars appears to have been able to sustain microbial life in the past, they’ve never been sure about how long that might have been possible. Researchers still have no firm answer, but they now have a better understanding of how long the habitable era on Mars may have lasted. If there used to be microbial life on Mars, its longevity could affect how and where we search for evidence. The longer such life lasted, the more likely it is that Curiosity or another explorer, human or robot, might find it.