Tuesday 29th September 2015

Nasa scientists find evidence of flowing water on Mars
Researchers say discovery of stains from summertime flows down cliffs and crater walls increases chance of finding life on red planet
Liquid water runs down canyons and crater walls over the summer months onMars, according to researchers who say the discovery raises the chances of being home to some form of life.
The trickles leave long, dark stains on the Martian terrain that can reach hundreds of metres downhill in the warmer months, before they dry up in the autumn as surface temperatures drop.
Images taken from the Mars orbit show cliffs, and the steep walls of valleys and craters, streaked with summertime flows that in the most active spots combine to form intricate fan-like patterns.
Scientists are unsure where the water comes from, but it may rise up from underground ice or salty aquifers, or condense out of the thin Martian atmosphere.
“There is liquid water today on the surface of Mars,” Michael Meyer, the lead scientist on Nasa’s Mars exploration programme, told the Guardian. “Because of this, we suspect that it is at least possible to have a habitable environment today.

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The water flows could point Nasa and other space agencies towards the most promising sites to find life on Mars, and to landing spots for future human missions where water can be collected from a natural supply.
“Mars is not the dry, arid planet that we thought of in the past,” said Nasa’s Jim Green. “Liquid water has been found on Mars.”
Nasa announce that there are watery flows on the surface of Mars during the red planet’s summer months.
Some of the earliest missions to Mars revealed a planet with a watery past. Pictures beamed back to Earth in the 1970s showed a surface crossed by dried-up rivers and plains once submerged beneath vast ancient lakes. Earlier this year, Nasa unveiled evidence of an ocean that might have covered half of the planet’s northern hemisphere in the distant past.

Dark narrow streaks called recurring slope lineae emanate out of the walls of Garni crater on Mars. Photograph: Nasa/AFP/Getty Images
But occasionally, Mars probes have found hints that the planet might still be wet. Nearly a decade ago, Nasa’s Mars Global Surveyor took pictures of what appeared to be water bursting through a gully wall and flowing around boulders and other rocky debris. In 2011, the high-resolution camera on Nasa’s Mars Reconnaissance Orbiter captured what looked like little streams flowing down crater walls from late spring to early autumn. Not wanting to assume too much, mission scientists named the flows “recurring slope lineae” or RSL.
Researchers have now turned to another instrument on board the Mars Reconnaissance Orbiter to analyse the chemistry of the mysterious RSL flows.Lujendra Ojha, of Georgia Institute of Technology in Atlanta, and his colleagues used a spectrometer on the MRO to look at infrared light reflected off steep rocky walls when the dark streaks had just begun to appear, and when they had grown to full length at the end of the Martian summer.

Nasa faces contamination dilemma over Mars water investigations
Curiosity rover already on red planet cannot study streaks left by flowing water because it could be carrying bugs from Earth

Nasa scientists may still be celebrating their discovery of liquid water on Mars, but they now face some serious questions about how they can investigate further and look for signs of life on the red planet.
The problem is how to find life without contaminating the planet with bugs from Earth.
The Guardian view on the discovery of liquid water on Mars: cause for great celebration
Editorial: Now the search is on to find living organisms on the red planet. Even traces of primitive microbes would rank among the most important discoveries in history

Researchers at the space agency are keen for the Curiosity rover to take a closer look at the long dark streaks created by liquid water running down craters and canyon walls during the summer months on Mars.
But the rover is not sterile and risks contaminating the wet areas with earthly bugs that will have hitched a ride to the planet and may still be alive.
The vehicle has been trundling around the large Gale crater looking for evidence that Mars was habitable in the ancient past. It hasso far uncovered evidence of past river networks and age-old lakes.
However, the dark, damp streaks, called recurring slope lineae (RSL), are a different prospect. Because they are wet at least part of the time, they will be designated as special regions where only sterile landers can visit. But such a restriction could hamper scientists’ hopes of looking for current life on Mars.
“There will be heated discussions in the next weeks and months about what Curiosity will be allowed to do and whether it can go anywhere near the RSLs,” said Andrew Coates of University College London’s Mullard space science laboratory.
Nasa announces that there are watery flows on the surface of Mars during the red planet’s summer months.
“Curiosity now has the chance, for example, to do some closer up, but still remote, measurements, using the ChemCam instrument with lasers, to look at composition. I understand there is increasing pressure from the science side to allow that, given this new discovery.”
An organisation called the committee on space research (Cospar) draws up the rules on what is called planetary protection, which exist to prevent missions from Earth contaminating the pristine environments of other worlds. Landers that are searching for life must be exceptionally clean, and fall under category IVb, but those entering special regions are category IVc missions and must be cleaner still.
Curiosity was designed for category IVb, and under Cospar rules is not allowed to enter areas where water might be flowing. But that might be up for discussion. Nasa’s Jim Green argues that the intense radiation environment on Mars, in particular the ultraviolet light, might have killed any bugs Curiosity carried into space, and so may be clean enough to move into the sites.
A recent report from the US National Academy of Sciences and the European Science Foundation, however, suggests that UV light might not do the job, and could make matters worse. “Although the flux of ultraviolet radiation within the Martian atmosphere would be deleterious to most airborne microbes and spores, dust could attenuate this radiation and enhance microbial viability,” the report states.
Curiosity could inspect the flows from a distance, using its onboard laser to take more measurements of the dark streaks. But a more controversial option is to find a flat region at the bottom of one of the flows, and scoop up some Martian soil for analysis.
The next rover due to land on the planet is a joint mission named ExoMars from the European and Russian space agencies, set to launch in 2018. The plan is for the rover to drill up to two metres into the Martian soil to look for life past or present.
“For the ExoMars 2018 rover, the planetary protection is being very carefully looked at and a combination of baking and cleaning is planned to avoid any possible mishaps and make sure it is IVb so it can make the best possible life-searching measurements in the regions it can get to,” said Coates, who is leading the camera team on the rover.

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