These images from the
High Resolution Imaging Science Experiment (HiRISE) camera on NASA's
Mars Reconnaissance Orbiter show how the appearance of dark markings on
Martian slope changes with the seasons. Image credit:
NASA/JPL-Caltech/Univ. of Arizona › Full image and captionc1
NASA's Mars Reconnaissance Orbiter has revealed to scientists slender dark markings -- possibly due to salty water - that advance seasonally down slopes surprisingly close to the Martian equator.
"The equatorial surface region of Mars has been regarded as dry, free of liquid or frozen water, but we may need to rethink that," said Alfred McEwen of the University of Arizona in Tucson, principal investigator for the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) camera.
Tracking how these features recur each year is one example of how the longevity of NASA orbiters observing Mars is providing insight about changes on many time scales. Researchers at the American Geophysical Union meeting Tuesday in San Francisco discussed a range of current Martian activity, from fresh craters offering glimpses of subsurface ice to multi-year patterns in the occurrence of large, regional dust storms.
The seasonally changing surface flows were first reported two years ago on mid-latitude southern slopes. They are finger-like features typically less than 16 feet (5 meters) wide that appear and extend down steep, rocky slopes during spring through summer, then fade in winter and return the next spring. Recently observed slopes stretch as long as 4,000 feet (1,200 meters).
McEwen and co-authors reported the equatorial flows at the conference and in a paper published online Tuesday by Nature Geoscience. Five well-monitored sites with these markings are in Valles Marineris, the largest canyon system in the solar system. At each of these sites, the features appear on both north- and south-facing walls. On the north-facing slopes, they are active during the part of the year when those slopes get the most sunshine. The counterparts on south-facing slopes start flowing when the season shifts and more sunshine hits their side.
"The explanation that fits best is salty water is flowing down the slopes when the temperature rises," McEwen said. "We still don't have any definite identification of water at these sites, but there's nothing that rules it out, either."
More - Link >>> http://www.jpl.nasa.gov/news/news.php?release=2013-361
Sources: NASA, Jet Propulsion Laboratory / California Institute of Technology
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