Martian water may come from deep reservoirs
In 2015, NASA announced the discovery of water flowing down the sides of craters on Mars. NASA calls them Reoccurring Slope Lineae, RSL for short. This seemed to answer the question of whether liquid water currently existed on Mars. And since liquid water is believed to be a prime requirement for life, the discovery also reinvigorated the discussion of life, even if only microscopic, on the red planet. You can see a NASA video montage of some RSLs at https://youtu.be/H44-XrGH5IQ.
In 2017, some researchers published papers suggesting RSLs were not from water but consisted of sand sliding down the slopes, driven by carbon dioxide that sublimated from dry ice just below the surface. Carbon dioxide, being a relatively heavy gas, flows downhill and carries sand grains with it. The researchers suggested that the sand just below the surface might be darker, having not been bleached by UV radiation from the sun.
The consensus of scientific opinion, however, rested with water flow, but many wondered if water just below the surface of the cold planet could never melt. Recently, Essam Heggy, a research scientist at the University of Southern California and NASA’s Jet Propulsion Laboratory, and Abotalib Z. Abotalib, a postdoctoral research associate at USC, suggested that the flows are triggered not by near-surface water but rather from deep below the surface.
“We propose an alternative hypothesis, that they originate from a deep, pressurized groundwater source, which comes to the surface, moving upward along ground cracks," said Heggy.
They compared Martian geological features to similar ones on Earth and determined that heat flow in the Martian subsurface was similar to that in desert regions here on Earth. This research, the two concluded, indicates that RSL water is probably coming from deeply buried, briny aquifers.
This even explains the seasonal aspect of the flows.
“The system shuts down during winter seasons, when the ascending near-surface water freezes within fault pathways and resumes during summer seasons when brine temperatures rise above the freezing point," the researchers wrote.
The new study says nothing about the existence of life on Mars, but it will surely strengthen arguments for at least microbial Martians living below the surface.
May highlights: On the May 10, look for the crescent moon in the western sky around 9 p.m. It sits almost directly in the center of one of the brightest star clusters visible from Oklahoma, the Beehive cluster. The moon’s glare will block it from your view, but it will be a fantastic sight in binoculars. The sun will have set more than an hour earlier, so only your local light pollution may hinder your view.
If you happen to be up in the wee hours of the morning on the May 23, go outside and find the nearly full moon in the south. You’ll see Saturn roughly a fist-width in the 1:30 position from the moon. On the same line, halfway between them, sits Pluto, our former ninth planet. You’d need a good-sized telescope to see it, but you’d know where to point it.
Planet visibility report: As the month begins, Mercury, Venus, Saturn and Jupiter all shine in the pre-dawn sky, although Mercury is too close to the sun for visibility. Only Mars is visible after sunset, low in the west, setting two and a half hours after the sun. Mercury and Venus dive towards the sun, and Mercury doesn’t reappear in the evening sky until early June. Saturn remains in the morning sky and Jupiter rises around midnight all month. New moon occurs on the June 4 with full moon following on the June 18.
Wayne Harris-Wyrick is an Oklahoma astronomer and former director of the Kirkpatrick Planetarium at Science Museum Oklahoma. Questions or comments may be emailed to email@example.com.