NEW EVIDENCE: Streaky features extending down Martian slopes could be caused by watery brines on the Red Planet.
Image: Courtesy of NASA/JPL/University of Arizona
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In the long hunt for water on Mars, researchers may have finally caught sight of flowing liquid.
High-resolution photographs from NASA's Mars Reconnaissance Orbiter (MRO) show dark, transient features on slopes in several midlatitude locations in the southern hemisphere. The features have appeared in Mars's southern spring across multiple years since the probe entered orbit in 2006, grow in length as they extend downhill, and then fade in late summer or early fall. The new features, which carry the purposefully uncontroversial moniker of recurring slope lineae, or RSL, were announced in a study in the August 5 issue of Science.
The cause of the RSL is unknown, but liquid brines just below the surface could well fit the bill. "We're not ruling out any reasonable explanation at this point," says lead study author Alfred McEwen, a planetary scientist at the University of Arizona in Tucson. The researchers have explored nonliquid processes such as rock slides, but McEwen notes that the timing of the surface markings' appearance and growth seems incompatible with dry phenomena. "There may be someone more clever than us that does come up with something," he says.
Until that happens, however, flowing water is a compelling explanation—and one that opens the door to speculation of life in the Martian soil. "This is the most promising place for water [on Mars] in some place that isn't too cold for life as we know it—and for water that is flowing," McEwen says. The southern slopes where the RSL occur are relatively temperate for the Red Planet, with peak temperatures that rise above 0 degrees Celsius in the summer.
Mars has no shortage of water in the form of ice buried below the surface. And planetary scientists think that the Martian landscape had liquid water billions of years ago. Several lines of evidence for more recent or even extant water on Mars have arisen in the past few years, including a controversial claim that NASA's Phoenix lander photographed droplets of water on its own struts in 2008. Phoenix briefly explored the frigid Martian arctic, so any water it may have encountered must have contained salts and chemicals called perchlorates to enable a very low freezing point.
If the slope streaks photographed by MRO, which occur in warmer locales, are indeed caused by water, that liquid would also be salty. "Mars is just a very salty place," McEwen says. "Any water that flows at the surface or subsurface gets salty." Brines of magnesium chloride, sodium chloride, calcium chloride or iron sulfates all have freezing points that match the MRO observations.
A spectrometer on board MRO was unable to identify the spectral signature of water from the RSL regions, so McEwen and his colleagues suspect that the ground itself is dry and that any liquid flows occur just below the surface.
James Head, a planetary scientist at Brown University who did not contribute to the new study, notes that the question of whether changing surface features on Mars are associated with water or watery brines has beleaguered planetary science for decades. The new discovery, he says, "brings us much closer to understanding the role of such liquids in shaping Mars, even in the current environment."
The potential signature of liquid water may have gone undetected in the orbiter's voluminous catalogue of data and imagery had it not been for the work of a University of Arizona undergraduate. Lujendra Ojha was working to identify changes in images taken by MRO of the same locations at different times when he noticed the transient markings on southern slopes.
"We had them hiding in our images for years without our noticing them," McEwen says. "It's hard to appreciate their significance until you see the images separated by a large amount of time."
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10 Comments
Add CommentCool stuff, mostly theories, but the fact that there is some unexplained phenomenon going on on the Martian surface is still pretty cool
Reply | Report Abuse | Link to thisIt's hard to say that those channels were cut by water. Too bad that the report did not mention the temperature and the pressure of those channels at the time the photos were taken. Those channels seem to have been cut by some kind of a liquid (or mixture of liquids) alright. From our knowledge of liquids based on the ambient conditions of our earth, liquids can be water, mercury, carbon tetrachloride, acetone...etc. By scientific process of elimination, if other liquids (except water) are proved not possible, then we can say it is water. Even then, we still have to know the physical and the chemical properties of the substrate (such as the hardness) on which the channels were built for the reported time duration, assuming the gravity of Mars, the inclination of the channels, and other parameters are known. That means there is some hope of applying CFD (Computational Fluid Dynamics) to simulate the specific process of channel cutting. Hope to see more work by the scientists in this investigation. Thanks to Scientific American for reporting.
Reply | Report Abuse | Link to thisThe report focuses on seasonal temperature variations to initiate phase change from solid to liquid whether it be ice to water or the same for CO2 or other substances if conditions permit. Another seasonal effect that could be considered initiating change is the solar tide. Is it possible that tidal forces during the southern spring & summer could trigger tremors that result in rock slides or localized liquefaction and flow of fine sediment or the release of deeper solid CO2?
Reply | Report Abuse | Link to thisNot knowing the magnitude of earthquakes on Mars, I doubt that liquefaction or flows would occur without water, as both of these are started due to loss of soil strength due to build up of excess pore water pressures occurring below a water table. Is it possible that these are wind blown deposits?
Reply | Report Abuse | Link to thisThousands of retired Keebler elves went out there with their tiny retired-elf shovels and carefully dug these "erosion rifts" solely to confuse the NASA sats.
Reply | Report Abuse | Link to thisThe geo-sync weather Martian sat photos clearly show the legions of elves doing the job. Soon to be laid off US space workers (NASA is now depricated) colluded by selectively editing which photos to show us.
If you look V E R Y closely, you see the little elfin footprints all over the rifts. Sloppy photoshop work guys.
Got any better photos?
4karats: "It's hard to say that those channels were cut by water."
Reply | Report Abuse | Link to thisWho says these are channels? I assumed they were sand moistened by water from below.
If we might be sending people to Mars, this looks like another potential use for a potential invention of mine, a better way to separate salts from water and maybe salts from each other. I haven't convinced anyone yet that it would work, but have disproven the one meaningful argument. Contact danrob@efn.org if you're interested. I gave up on it when I came to feel that solving one environmental problem would only lead to more population growth, which would make other problems worse. With the present state of the world, I feel it's too late to worry about such long-term problems.
racer 79: The existence of salt water on tghe surface of Mars is among the least of the cool surprises and great lessons that planet has in store for us, the greatest of which is the clear way in which Mars inhabitants destroyed their own enviroment with deforestation and hot house CO2 that forced their civilization underground, which gave them motive to visit earth to try to help us realize what we were doing to our own environment toward the end of our last ice age brought on by indusatrialization and practices that made us sitting ducks for the comet that struck the North Pole about 10.5 to 11 milennia ago which caused Arctic Ocean earthquKWA ns tsunamies that Distributed the polar waters around the northern hemisphere and convinced the inhabitants of the Martian Civilization they had to immigrate to Earth in enough numbers to influence our cultural and religious development!
Reply | Report Abuse | Link to thisQuinn the Eskimo:
Reply | Report Abuse | Link to thisThe indiginous peoples of some of the sub-polar areas of the Berring/Farting Seas (including some on St. Lawrence Island who remember the stories of their "guardians are considerably more open minded than you Eskimos. Now I understand why they were insulted when I called them Eskimos!
It is just a change in color with the seasons. Get darker in summer and early fall. Then goes light the rest of the time. Looks like an algae is growing when it gets warm enough to melt some of the brine in the soil. When it cools off the algae dies back till next year.
Reply | Report Abuse | Link to thisseems like a repeat of Schiaparrili's comment of "channels" which was misconstrued as "canals" by those who had an obsession to believe as such.
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