Salty water flows boost hope for life in Mars

An area that appears when temperatures rise above minus 23 degrees Celsius, and disappears when temperatures fall below that.

The evidence that liquid water flows on the surface of Mars was discovered by Lujendra Ojha, a researcher at Georgia Tech, and Alfred McEwen, professor of the Lunar and Planetary Institute at University of Arizona State University, who analyzed high-resolution photos from the Mars Reconnaissance Orbiter.

The researchers paid attention to a dark slope that disappears in cold winter but only appears in warm summer. The areas that have been named ‘Recurring Slope Lineae (RSL)’ is in the shape of a narrow streamlet measuring 5 meters wide and 100 meters long, and its dark slope appeared when temperatures rose above minus 23 degrees Celsius, and disappeared when temperatures dropped below that. In satellite photos, places where water exists look dark while places where ice exists look bright. For this reason, scientists conjectured that RSL is a phenomenon that emerges as water containing salty substances flows on Martian surface, but previously there was no clear evidence for that.

The researchers analyzed spectrum (information on lights emitted from Mars) from RSL sites that the Mars Reconnaissance Orbiter surveyed from 2006, and secured critical evidence that it is phenomenon that emerges as water containing salty substances including sodium chloride and magnesium chloride flows. Liquid water can flow even in freezing environment on Mars, because the water contains salts including salt (sodium chloride). If water contains salts, its freezing point declines, enabling the water to flow. It is due to the same principle that seawater does not freeze even at subzero temperatures on Earth, and calcium chlorine is sprayed on the road on snowy days to prevent road surface from being frozen.

There was a large ocean on Mars until 4 billion years ago, but most of the water disappeared from the surface due to climate change arising from unknown cause. Researchers say that research must continue to find where ‘water flows’ that have been newly discovered originate from. Hypothesis suggests there is a possibility that salty substances absorb moisture from surrounding areas before melting on its own to cause water to flow, or that a layer containing water exists under the surface.

In a press conference on Monday (US time), John Grunsfield, associate administrator for the Science Mission Directorate at NASA, said, “Our Mars exploration was meant ‘for tracing water’ to seek life in space, and what we have speculated for a long time has been scientifically verified now,” adding, “This is an important step forward.”

Yoon Seong-cheol, professor of physics and astronomy at Seoul National University, said, “Water in liquid form is the most important condition for life to survive, and the discovery may add to the probability that microorganisms survived in the past or are surviving today,” adding, “When exploring Martian surface with water in the future, they would use caution to not disrupt the Martian ecosystem that may exists there.”

The study was published in ‘Nature Geoscience,’ a sister publication of the journal Nature, on Monday.