In the past,Mars was basically regarded as a vast red desert with little likelihood of ever having hosted life,let alone presently harbouring it.Now,though,recent observations of Mars by the HiRISE,or High Resolution Imaging Science Experiment,aboard NASA's Mars Reconnaissance Orbiter,have changed the picture drastically.A number of scientists gave a press briefing Monday morning on the epochal findings,including Jim Green,Director of Planetary Science at NASA headquarters in Washington;Michael Meyer,Lead Scientist,NASA Mars Exploratory Program;Lujendra Ojha,Georgia Institute of Technology,Atlanta;Mary Beth Wilhelm,NASA Ames Research Center,Moffett Field,California and Georgia Tech;and Alfred McEwen,Principal Investigator,HiRISE,Univrsity of Arizona,Tucson.Also contributing to the NASA Science Update was John Grunsfeld,5-time NASA Astronaut and Associate Administrator.
The scientists indicated that we're starting to put together a much more interesting,dynamic and complex picture of Mars.Our journey to Mars is a science-led mission right now,but it's even more important to send planetary biologists and geologists to Mars.It really is a fascinating planet that once had salty seas,freshwater lakes and snowy peaks,with a water cycle like earth's.Did life arise on Mars once,and can we find out did any survive?Is there life on Mars today?The new data suggests it would be possible there is life today on Mars.Three billion years ago,Mars had an extensive atmosphere;a huge ocean up to a mile deep;but something happened.Mars suffered a major climate change and lost its surface water,yet Mars soils are moist and hydrated,full of water,and there is much more humidity in its atmosphere than was previously believed.Mars is not the dry,arid planet that we thought.Under certain circumstances,liquid water has been found on Mars,the HiRISE data show,in a feature known as Recurring Slope Lineae,which are dark streaks that form in late spring,grow through the summer and disappear in the fall.The broader distribution and more expansive latitudes of the RSL than expected are evidence of flowing water on Mars,as revealed by multiple spacecraft and observations,as set forth in the new article "RSL:Spectral Evidence for Hydrated Salts in RSL on Mars" in Nature Geoscience 28 September 2015.*
An animated sequence of the RSL cycle was shown at the update.HiRISE has observed this in the last four years or so.The RSL form at different times and temperatures and latitudes on Mars.They are seeps of water and seep through the surface layer and darken it.The seeps have been noted in three regions:
1.the southern mid-latitudes;
2.Valles Marineris;
3.Acidalia Planitia.
They occur in craters.The key evidence was missing until now:their chemical identity.This has been ascertained by the CRISM instrument on the MRO.It can observe the surface in various wavelengths;the interaction of light with the surface material indicates if there is any evidence of flowing water.We found that salt crystals composed of salt and chlorine when hydrated show the presence of molecular water in their crystal structure;molecular water is trapped inside the salt structure.The source of the water is either RSLs or some other processes-regardless,these crystals are formed by contemporary flowing water on Mars.These hydrated salts in the slopes means contemporary flowing water is forming them.Pure liquid water is highly unstable on the surface of Mars;but salty water doesn't evaporate as quickly until there is a higher temperature.*
RSLs are formed by flowing liquid briny water on the surface of Mars.The broader implications are:
more habitable conditions on the surface of Mars than previously thought.Further astrobiological and chemical analysis may show the water to be an important resource for human explorers on Mars,decreasing the cost of manned expeditions as a source of drinking water and oxygen.In principal,you could even make solid rocket fuel from the hydrated salt.
On earth,everywhere we find water,there is life.We now have great opportunities to be in the right locations to investigate that.We now are at a point technologically to go there,ask the question,and answer it.With HiRISE,we can make a better,more methodical search for life.Is there an aquifer network on Mars?It's very likely there is life in the Martian subsurface,microbial life.A number of upcoming NASA and ESA/Russia missions will help with our search.*
Mars is looking more and more habitable;the resources are there.A very methodical approach and rigorous scientific program will enable the setting of parameters and the design of manned missions.It is more feasible for missions than ever before.These are huge steps for us to plan the right resources to support human explorers in the future,NASA believes.
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