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Martian Moisture

photo - surface of Mars

A false-color image shows streaks, believed to be flowing water, at the Hale Crater on Mars. Image credit: NASA/JPL, University of Arizona

A study led by Georgia Tech scientists has provided the strongest evidence yet that there is intermittent flowing water on modern Mars.

Using instruments on NASA’s Mars Reconnaissance Orbiter (MRO), researchers measured spectral signatures of hydrated minerals on slopes where mysterious, possibly water-related streaks have been found on the red planet. These streaks, known as recurring slope lineae (RSL), form and snake down the planet’s steep slopes during warm seasons when temperatures exceed -10 degrees Fahrenheit. They disappear at colder times during the Martian year.

“Something is hydrating these salts, and it appears to be these streaks that come and go with the seasons,” said Lujendra Ojha, a Ph.D. student in Georgia Tech’s School of Earth and Atmospheric Sciences. “This means the water on Mars is briny, rather than pure. It makes sense because salts lower the freezing point of water. Even if RSL are slightly underground, where it’s even colder than the surface temperature, the salts would keep the water in a liquid form and allow it to creep down Martian slopes.”

The researchers believe that the signatures are caused by hydrated minerals called perchlorates. Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as -94 degrees Fahrenheit. On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.

photo - surface of Mars
Image shows dark narrow streaks called recurring slope lineae flowing out of the walls of Garni Crater on Mars. The streaks are up to a few hundred meters in length. Credit: NASA/JPL, University of Arizona.

Perchlorates have previously been discovered on Mars. The Phoenix lander and Curiosity both found them in the planet’s soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts. However, this study of RSL detected perchlorates in entirely different areas from where the landers explored.

“We’re only able to receive data on these RSL locations in mid-afternoon, when the air is dry and the morning humidity is almost gone,” said James Wray, a Georgia Tech assistant professor in the School of Earth and Atmospheric Sciences. “When future spacecraft arrive in the planet’s orbit, we could see larger, wetter RSL at earlier times of the day. This could just be the tip of the iceberg.”

The findings were reported in the journal Nature Geoscience.

— Jason Maderer

text - Humans on Mars

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