Darkened vertrical streaks hint at spring and summer flows of salty water on Mars. Photo Credit/NASA
Recently discovered linear features on sloped Martian terrains suggest water flows on some regions of the Red Planet, raising the prospects for conditions favorable for life, say scientists.
The features were imaged by NASA’s Mars Reconnaissance Orbiter, a spacecraft that has been orbiting the neighboring planet with high resolution cameras since March 2006.
The imagery reveals darkened troughs that form on crater walls and other sloping terrain in the late summer through summer. The narrow depressions that stretch several hundred yards fade in the winter and return as temperatures rise. They are grouped in the mid-latitudes of the planet’s southern hemisphere.
“The best explanation for these observations so far is the flow of briny water,” said Alfred McEwen of the University of Arizona. McEwen is the principal investigator for the MRO’s High Resolution Imaging Science Experiment (HiRISE) and lead author of a report on the spacecraft observations that appeared in Thursday’s edition of the journal Science.
Launched in August 2005, NASA's Mars Reconnaissance Orbiter has been circling Mars since March 2006. The orbiter's primary mission ended in 2010. Image Credit/NASA image
Alternative explanations include flows of carbon dioxide or pure water. However, the flow conditions appear to be too warm for carbon dioxide and too cold for pure water. Water with concentrations of salt high enough to lower the freezing point offer the most likely explanation for the features.
If the water flows are on the surface, the moisture quickly evaporates in the thin Martian atmosphere. It’s possible the flows are in the shallow subsurface.
The first spacecraft to visit Mars four decades ago spied long channels that hinted at a past warmer global climate — a period marked by an atmosphere thick enough for water to flow and pool on the planet’s surface. The more recent Mars Phoenix mission landed near the planet’s North Pole in 2008 and discovered a layer of water ice buried just below the surface.
Water in the liquid phase on Mars increases the odds of habitats where life might arise and flourish.
“NASA’s Mars Exploration Program keeps bringing us closer to determining whether the Red Planet could harbor life in some form,” NASA Administrator Charles Bolden said, “and it reaffirms Mars as an important future destination for human exploration.”
In late November, NASA plans to launch the Mars Science Laboratory, with a nuclear powered rover named Curiosity. The big rover, scheduled to land in August 2012, is equipped with instrumentation to examine the soil and rocks of Gale Crater for evidence of conditions suitable for microbial life.