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Flowing water on Mars

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Scientists have recently discovered the existence of flowing water on Mars. It’s been known for some time that flowing water did once occur on the red planet’s surface. A raft of geological evidence shows us that 4.1 billion years ago (only 0.4 billion years before the formation of Earth), liquid water flowed on the surface, eroding a network of river valleys, lakes, and oceans. Pictures of the planet taken by NASA in 1970 also show evidence of dried-up rivers and lakes etched into the Martian surface.
A vast, one mile deep, ocean that once existed in the Northern hemisphere and covered one fifth of the planet’s surface was revealed in March earlier this year. Mars definitely had surface water, and lots of it too. So where did it all go? Because Mars is only half of the Earth’s diameter and 38% of its gravity, it was easier for gasses in the upper layer of the original atmosphere to boil off into space. This made it easier for meteors to strike the surface, thus displacing water and thinning the atmosphere further. As the atmosphere disappeared, the pressure and heat that was keeping the water in liquid form also disappeared with it. 87% of the planet’s water wafted off into the vacuum of space. The 13% that remains is ‘heavy water’ and therefore didn’t drift off into space but condensed and froze to form polar ice caps. Heavy water is just like normal water, H2O, but one of the hydrogen atoms is deuterium, a stable heavy isotope of hydrogen (consisting of a proton and a neutron, whereas hydrogen only consists of a proton).
In 2011 the Mars Reconnaissance Orbiter (MRO), a $720 million spacecraft launched in 2005, discovered what appeared to be small black streams flowing down crater walls during late spring, however, no water was positively identified. These streams were therefore unassumingly named recurring slope lineae or RSLs. Researchers have since used a spectrometer onboard the MRO to analyse infrared light reflections from these RSLs when they appear in the spring and again in the late Martian summer when they had grown to full length. They discovered that the RSLs contain hydrated salts chlorate and perchlorate; hallmarks of flowing water that once meandered down the slopes of steep cliffs.
On the 28th of September it was discovered that water was in fact flowing down these RSLs. Researchers are still unsure of where the water is coming from. Underground sources and salty aquifers are a few proposed options. The most likely source however, is the chlorate and perchlorate salts found in the RSLs. By absorbing water from the atmosphere they become hydrated, then when enough water is gathered, brine is formed and begins to trickle down the sides of craters and canyons, producing vast networks of fan-like black streaks in the red sediment. The streams only appear in the summer months when the surface temperature is -23°C or above. The water can flow at such low temperatures because of its salinity; the many particles in the water prevent ice crystals from forming and turning it into ice.
These brine streams are our current best hope for finding extraterrestrial life. Neil deGrasse Tyson, an American astrophysicist, stresses the importance of finding water in the search for life: “Where there’s water on Earth, you find life as we know it. So if you find water somewhere else, it becomes a remarkable draw to look closer to see if life of any kind is there, even if it’s bacterial, which would be extraordinary for the field of biology”.
There are examples of organisms alive today on Earth that can survive extremely salty conditions, similar to the perchlorate-based water of the Martian streams. These organisms are called extremophiles and, in relation to humans, survive in extreme conditions. If life has adapted to extreme conditions such as high temperature, acidity, and salinity on Earth, what’s to say it hasn’t already on another planet? On Earth, a group of bacteria called halobacterium thrive in highly saline environments and brine shrimp, popular food of flamingos, happily inhabit waters of up to 25% salinity (the average salinity of seawater is 3.5%).
The brine streams, a potential source of water for a human expedition to Mars, could be the next step to solving the puzzle of a manned mission to the planet. Figures announced in the U. S. National Space Policy in 2010 state that NASA is developing technologies that will allow humans to land on an asteroid by 2025 and eventually the red planet sometime in the 2030s. Mars once had conditions suitable for life, placing humans on the ground may uncover fossilised ancient alien organisms. Unlikely to be anything that has evolved on Earth, these organisms would provide insights into an evolutionary process dramatically different from anything studied before.
NASA are currently preparing people to venture on this one-way journey. At Mauna Kea, Hawaii, six people are living in a dome for twelve months to simulate living on Mars. To rival NASA, Mars One (a non-profit organisation based in the Netherlands) plans to establish a permanent human settlement on Mars. The first manned mission is scheduled to depart in 2026, with subsequent missions departing every 26 months after. A reality TV program documenting the journey is a proposed form of partial funding for the project.
The discovery of flowing water on Mars is changing what we’ve thought about the red planet for decades and the way we view our universe.

As technology continues to rapidly develop throughout the 21st century and mankind tentatively reaches its mechanical hand out into the vastness of space, new discoveries will come flooding in. We’ve found water; will we find life next?

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Jack Greenhalgh

Science Editor 2015/16

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