Sometimes Liquid Water Flows On Mars

Erin Guinan is studying a Masters Degree in Astronomy & Astrophysics and is on her way to becoming a star.

For centuries, human beings with inquisitive minds have explored some of the most fundamental questions of all humanity – the meaning of life and the potential for life to exist elsewhere within the universe. As a result, the fields of astronomy and astrobiology are rich and complex – largely due to the ever increasing technological capabilities of modern society, and the inherent human desire to explore for answers.

The discovery of life of extraterrestrial origin would be one of the most important scientific discoveries of our time. Since the dawn of the space age, a number of missions have explored the Solar System in unprecedented detail in a bid to understand its origins as well as the potential habitability for extraterrestrial life. Based on our current understanding of the biological requirements for life on Earth, the presence of water would be the first element considered, as it is a vital requirement for life itself.

It has long been believed that out of all of the planets in the Solar system, Mars has the highest probability of supporting extraterrestrial life. It is only half the size of the Earth, however both planets fall within the proposed habitable zone – a region in which the presence of liquid water is possible. There is no doubt that Mars and Earth share a lot of similarities. Mars takes just 37 minutes longer than Earth to rotate once on its axis. Both planets have tilted axis – Mars at 25 degrees, Earth at 23.5 degrees – causing both planets to exhibit seasons and Polar Regions. Other similarities between the two terrestrial planets include volcanism (though extinct on Mars), deep canyons, Polar Ice caps (which expand and contract on the Martian surface), and evidence of ancient dry riverbeds. Current conditions on the planet are inhospitable for the existence of most forms of life. The Martian atmosphere is extremely thin – composed of 95% carbon dioxide. Average surface temperatures on Mars sit at a chilling -60 ºC, with night time temperatures often falling below -100 ºC.  Yet with such differences, Mars remains the planet that most resembles Earth, representing a beacon of potential research and exploration.

The search for evidence of life on Mars is a continual process, with advancements in technology assisting in the search missions. Today, a number of missions have orbited, surveyed and explored the surface of Mars in detail, gathering a compelling amount of data to support the theory that conditions were once much more Earth-like in the past. This includes a wetter climate, thicker atmosphere and more importantly, a substantial presence of water covering 19% of the planet.

But then at 1.30am Tuesday morning Eastern Standard Time, NASA announced a groundbreaking discovery about Mars, confirming the presence of liquid water on its surface – sometimes.

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First discovered in 2011, a feature known as recurring slope lineae (RSL) became evident through images taken with the High resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter. At first, these long, dark narrow streaks – sometimes up to 100 metres in length – appeared to ‘streak’ down the Martian slopes; rather puzzling to scientists. These streaks occurred during the late spring on the slopes of the Southern hemisphere, yet disappeared once the Martian temperatures dropped over the coming months. Recent scientific findings have detected hydrated salts on the slopes in which RSL occurs which is highly suggestive of the presence of liquid water. However the source of the water itself remains largely a mystery.

One suggestion is that the RSL occurs from a process called atmospheric deliquescence in which the surface salts absorb any potential water vapour within the Martian atmosphere until the salt dissolves into a eutetic brine solution. This in turn, causes Mars to appear to ‘sweat’ with saltwater seeping down from its slopes. An alternate suggestion is that the source of the water lies deeper underneath the surface of Mars within an underground aquifer or a reserve of ice beneath the soil. Any life that could potentially – if at all – exist within this RSL would likely be of microbial origin.

Whether such conditions will be found to support life is one of the goals of current day research on Mars. The confirmation of RSL is not exactly a flowing river, yet it represents one giant leap in the search for liquid water, and thus the potential for extraterrestrial life. Many people see Mars as a ‘second’ Earth, with future scientific advancements endearing to see humans terraforming the Martian atmosphere in a bid to enable long term habitability on the planet.

The confirmation of RSL and hence liquid water on Mars provides an important stepping-stone in our quest to answer one of the most fundamental questions of all time: Are we alone in the universe? 

Photographer: NASA/JPL/University of Arizona

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