Washington: NASA`s Mars Reconnaissance Orbiter has revealed to scientists slender dark markings - possibly due to salty water - which may force them to rethink their plans about future explorations of the Red Planet.
Alfred McEwen of the University of Arizona in Tucson, principal investigator for the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) camera, said that while Mars probes are carefully sterilised before launch, there is a risk that microbes could make to Mars` surface.
He said that a 2008 report had concluded that tropical Mars is too dry for terrestrial life to survive there, making it a relatively safe landing zone but evidence of recurring damp spots in the Martian tropics could change that assessment.
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.
McEwan said that the explanation that fits best is salty water is flowing down the slopes when the temperature rises, asserting that they still don`t have any definite identification of water at these sites, but there`s nothing that rules it out, either.
This analysis used data from the Compact Reconnaissance Imaging Spectrometer for Mars and the Context Camera on the MRO as well as the Thermal Emission Imaging System experiment on NASA`s Mars Odyssey orbiter.
Water ice has been identified in another dynamic process researchers are monitoring with MRO. Impacts of small asteroids or bits of comets dig many fresh craters on Mars every year.
Twenty fresh craters have exposed bright ice previously hidden beneath the surface. Five were reported in 2009. The 15 newly reported ones are distributed over a wider range of latitudes and longitudes.
The paper has been published online on journal Nature Geoscience.