Planetary scientists may have discovered evidence of (salty) water flows on the surface of Mars, but their source and mechanism of activity are unknown.
Hundreds of thousands of years ago, liquid water was probably present on the surface of Mars, as has been inferred from the numerous channels that mark its surface. But the existence of water on the Martian surface today is the source of no little argumentation amongst planetary scientists.
So, the news that a team of scientists, led by Alfred S. McEwan of the Lunar and Planetary Laboratory, University of Arizona, Tucson, may have identified the tell-tale signs of “seasonal flows” (small channels attributable to downhill water movements) on certain slopes has got the astronomy and planetary science communities understandably excited.
Using repeat images from the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment (HiRISE ), the scientists were able to identify recurring slope lineae (RSL), which appear as dark markings on fairly steep (25 to 40 ) Martian slopes. The lineae (lines, or linage) appear to emanate from nearby bedrock outcroppings and proceed down slope. In a few cases, hundreds of such lines appear to emanate from the same source. The channels are estimated to be just .5 to 5 meters wide, and up to many hundreds of meters in length.
But what may be the clinching evidence of flowing water is the fact that the RSL emerge and then progressively lengthen in warm seasons, and shrink in colder ones.
According to the abstract, publishing this August 5 in Science Magazine*, ” RSL appear and lengthen in the late southern spring and summer from 48°S to 32°S latitudes favoring equator-facing slopes, which are times and places with peak surface temperatures from ~250 to 300 kelvin.”
And the explanation for these observations? “Liquid brines (salty waters) near the surface might explain this activity, but the exact mechanism and source of water are not understood.”
So, as always in science (especially that conducted on an alien planet), one discovery leads to many more puzzles and questions.
The strange markings and their apparent movement first came to the team’s attention after an undergraduate student, Lujendra Ojha (a cited author of the paper), detected the subtle shifts using a change detection algorithm as part of an independent study project.
Up until recently, some of the Martian surface was being mapped by “twin” rovers — Spirit and Opportunity — that had long out-lived their original 3 month missions and projected life spans. But in May, Spirit became trapped in sand and has not been heard from since. Currently, Opportunity is surveying the Endeavor crater, a 14 mile diameter depression near the red planet’s equator. It is expected that the this will be the intrepid rover’s final destination.
But who knows? Opportunity has proven itself more robust that previously supposed…So, there’s a slim chance that it might have go at one more mission: the quest for Martian water!
For more in depth information about the work and the lab, check out the LPL site news article Briny Water May Be at Work in Seasonal Flows on Mars.
Team members: Alfred S. McEwen, Lujendra Ojha, Colin M. Dundas, Sarah S. Mattson, Shane Byrne, James J. Wray, Selby C. Cull, Scott L. Murchie, Nicolas Thomas, Virginia C. Gulick
*Seasonal Flows on Warm Martian Slopes, McEwan et al, Science (on-line), 5 August, 2011
Author Comment: Gee, Mars may be the kind of place to raise your kids, after all…well, at least the kind of place to send a long-term, human space mission…
top photo: LPL, University of Arizona/NASA