The instruments of the Mars Reconnaisance Orbiter were crucial to confirming the intriguing finding, which raises the possibility of finding microbial life but presents new difficulties for future missions
Orbital spectroscopy technology was the key factor in NASA’s announcement yesterday that Mars has flowing water on its surface at certain times of the year. The agency pressed infra-red spectrometers on board the decade-old Mars Reconnaisance Orbiter (MRO) into service to check out dark narrow streaks which had been photographed creeping down the walls of craters during the Martian summer, and these instruments confirmed the presence of hydrated salts at three craters and one canyon.
MRO carries two instruments that were important for the discovery: a high-resolution camera called HiRISE, attached to the largest reflecting telescope ever carried on a deep-space mission, which was built by Ball Aerospace and Technology under the direction of the University of Arizona; and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), built by the Johns Hopkins University Applied Physics Laboratory and specifically designed to look for water.
This finding indicates two important things that were previously suspected but unconfirmed: that water is flowing on the Red Planet and also that chemistry is taking place. The salts found by the spectrometers, chlorates and perchlorates, lower the melting point of water in which they are dissolved, rendering it capable of flowing at the Martian summer temperature of approximately -23°C. The researchers responsible for the discovery, led by Lujendra Ojha of Georgia Tech in Atalanta, have published their results in Nature Geosciences.
What’s still unknown is the origin of the water in the streaks, which NASA named Recurring slope linaea (RSLs) when they were first observed in 2011. There are a variety of possibilities, said Tim O’Brien, Professor of astrophysics at the University of Manchester. “Is it seeping up to mix with salts on the surface to make the briny water? Or it this water coming from the atmosphere, as it does on Earth?”. The main possibilities are believed to be frozen salty acquifers in porous rocks below the surface; purer water frozen underground that mixes with salt deposits on the surface when it melts, or as O’Brien suggests, deliquescent salts absorbing water from the atmosphere. The last of these effects is seen on Earth in the Atacama Desert, and is the source of the only place in the desert where microbial life is found
And it’s this possibility which is currently exciting planetary scientists: flowing water is the most likely place to find traces of life, and this discovery raises the possibility that the Red Planet could still be the home of living things, rather than just traces of long-extinct life, as has been presumed. “Millions of years ago conditions on Mars were similar to what we have on Earth now.
“The presence of liquid water increases the possibility that there could be some microbial life forms still on the planet. But in itself it is not evidence for life,” O’Brien commented.
“All life as we know it needs water, now we have found water on Mars there could be life. They have found a key prerequisite for life but not life itself.”
But it also presents a further challenge for exploring Mars. Planetary hygiene is a key concern for probes visiting bodies on the Solar System: great care is taken that we do not contaminate our neighbourhood with microbes hitching a ride on our discovery machines. The ability of water to support life would make damp areas the riskiest places to visit, although also the most interesting: NASA and other agencies are sure to target these regions for future landings, whether of robotic probes like ESA’s ExoMars Rover, scheduled to land on Mars in 2019, or for proposed crewed missions.