“This is tremendously exciting,” James L. Green, the director of NASA’s planetary science division, said during a news conference on Monday. “We haven’t been able to answer the question, ‘Does life exist beyond Earth?’ But following the water is a critical element of that. We now have, I think, great opportunities in the right locations on Mars to thoroughly investigate that.”
NASA researchers using an imager aboard the Mars Reconnaissance Orbiter aircraft, detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the red planet. These dark streaks appear to be about 15 feet wide and 300 feet or more long, scientists said. These downhill flows, known as recurring slope lineae (RSL), often have been described as possibly related to liquid water. They apparently consist of wet soil, not standing water. In a paper published in the journal Nature Geoscience, the water is believed to contain certain salts – not ordinary table salt, but magnesium perchlorate, magnesium chlorate, and sodium perchlorate. The hydrated salts would lower the freezing point of liquid brine, just as salt on roads on Earth causes ice and snow to melt more rapidly.
The investigation showed the streaks absorb light at specific wavelengths associated with chemicals known to pull water from the Martian atmosphere in a process known as deliquescence, said Lujendra Ojha of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology, who first discovered the streaks on Mars in 2010. Ojha and his colleagues speculated at the time that they were seeing flowing water.
The chemicals allow the water to remain liquid at lower temperatures but also help keep it from boiling off in the thin atmosphere of Mars, the researchers said.
“These soggy streaks suggest that there are vast reserves of underground water, presumably the last remains of lakes that may have once dotted the landscapes of this planet," said Seth Shostak, senior astronomer and director of the Center for SETI Research, who was not involved in the new study. "Consequently, if life began billions of years ago during Mars' more clement youth, its progeny could still be hiding out a few feet underfoot," he said. "That would make the task of finding some red planet biology far easier."
It remains unclear where the water comes from. The researchers aren’t’ sure whether the water is flowing from a liquid-water aquifer, melting ice or another source. There could be several reasons that the RSL lines are forming, the researchers wrote in the journal. Discovering what precisely is causing the phenomenon is a mystery for the next round of investigations, said Michael Meyer, lead scientist for NASA’s Mars Exploration program.
Perchlorates have previously been seen on Mars. NASA’s Phoenix lander and Curiosity rover 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, the most recent study identified RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers. This is also the first time perchlorates have been identified from orbit. MRO has been examining Mars since 2006 with its six science instruments.
Well, it remains to be seen whether the recent discovery improves the odds of signs of life on Mars, but “It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future," said Michael Meyer.
James L. Green said the discovery announced Monday puts NASA in a perfect position to look for that life. "We haven't been able to answer the question, 'Does life exist beyond Earth?'. But following the water is a critical element of that. We now have, I think, a great opportunity to be in the right locations on Mars to thoroughly investigate that."