The narrow, dark streaks, or recurring slope lineae, flowing downhill on Mars are inferred to have been formed by contemporary flowing water.
The narrow, dark streaks, or recurring slope lineae, flowing downhill on Mars are inferred to have been formed by contemporary flowing water.

HiRISE Images Show Signs of Liquid Water on Mars

Former UA undergraduate Lujendra Ojha discovered possible water-related streaks on the red planet's slopes.
Sept. 28, 2015

New findings from NASA's Mars Reconnaissance Orbiter, or MRO, provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.

Researchers measured the spectral signatures of hydrated minerals on the planet’s slopes where mysterious, possibly water-related streaks are found. Lujendra Ojha first discovered the streaks in 2010 when he was a University of Arizona undergraduate.

The streaks, known as recurring slope lineae, or RSL, darken and appear to flow down the planet's steep slopes during warm seasons when temperatures exceed minus-10 degrees Fahrenheit and then fade during cooler times.

Ojha was using images from the orbiter's High Resolution Imaging Science Experiment, or HiRISE, which is managed at the UA. HiRISE observations have now documented RSL at dozens of sites on Mars. The new study pairs HiRISE observations with mineral mapping by the same orbiter's Compact Reconnaissance Imaging Spectrometer for Mars, or CRISM.

Ojha, now a graduate student at the Georgia Institute of Technology, is lead author of a report on these findings published Monday by Nature Geosciences.

"We only found the hydrated salts when RSL were widest, which suggests that either RSL or the processes that form RSL is the source of hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks," Ojha said.

Alfred McEwen, director of the UA Planetary Image Research Laboratory, said, "The presence of water on Mars today, however fleeting, raises the possibility of present-day life near the surface of Mars, so the RSL should be a key target for future exploration."

Ojha and his seven co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are probably a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate. Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus- 94 degrees Fahrenheit. On Earth, naturally produced perchlorates are concentrated in deserts.

McEwen, HiRISE's principal investigator, and CRISM principal investigator Scott Murchie of the Johns Hopkins University Applied Physics Laboratory are co-authors of the new report.