Sponges of Mars? Study suggests that water on the red planet could support life

RED PLANET. Mars seen by the viking orbiter. NASA / JPL / USGS image

It has long been thought that Mars was dry and barren – unable to shelter life. But research done in recent years indicates that there is very likely to be some brine today, including a possible underground lake. This has given rise to new hopes that there may be life on the red planet after all, depending on the living conditions in the water.

Now, a new study, published in Nature Geoscience, shows surprisingly that the brine deposits below the surface of Mars, especially near the poles, may contain molecular oxygen – which is essential for life on Earth. This is exciting because it is even more likely that the planet can support microbial life or even simple animals such as sponges.

3.8 to 4 billion years ago, the surface of Mars was very similar to that of the Earth and thus would have united the conditions of life. At that time, there was a thick atmosphere and white water on the surface, a global magnetic field and volcanism.

Today, the surface is dry and cold – 5ºC to 10ºC during the day and -100ºC to -120ºC at night. In fact, the atmospheric pressure is less than 1% of that of the Earth, which means that any flowing water would evaporate rapidly into the atmosphere. But he can remain trapped under the surface. Volcanism is also dead and only small-scale magnetic crustal fields remain to protect it from the sun's rays in the southern hemisphere. It is for these reasons that the current life on Mars was until recently considered highly improbable.

Evidence of badembly

We now know that there are however traces of methane on Mars, discovered by Mars Express and the Curiosity rover. The source of this methane could be either hydrothermal activity (the movement of heated water) or microbial life. On Earth, flatulent cows alone produce about 25% to 30% of the methane in the atmosphere. Either or both of these possibilities challenges our current understanding of the red planet, but if the source is life, it would obviously be an amazing discovery. The European and Russian trace gas control agency ExoMars is currently studying the source of this methane.

NASA Mars Reconnaissance Orbiter has also discovered seasonal features called "recurrent slope lines" – trail-shaped patterns that may indicate brackish water oozing to the surface. However, there are alternative explanations. Some scientists suggest that it would only act as sand motions. That said, rovers and landers have found substances, including calcium and magnesium perchlorates, near suspected seeps of water and at other locations on Mars, indicating the presence of brine.

It is thought that a lake is hiding under the polar ice cap south of Mars. NASA

More recently, ESA's Mars Express mission uncovered radar evidence of the presence of liquid water beneath the southern polar region of Mars – potentially an underground lake. This water, which also appears to be brine, would be an enormous 20 km wide and would be located 1.5 km below the surface.

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Read more: What could he live in a salt water lake on Mars? An expert explains

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The new study has calculated the amount of molecular oxygen that can be dissolved in liquid brines on Mars. This shows that the small amount of oxygen produced in the atmosphere could actually dissolve in brines at the temperature and pressure observed near the surface of Mars. With the help of an atmospheric model, the researchers then studied this solubility at different places on the planet and in time. Liquid environments containing dissolved molecular oxygen would be scattered over most of the Mars surface, but would be particularly concentrated near the poles, where conditions are colder.

Computer models show that this could lead to respirable oxygen levels for all aerobic microbes (insects requiring oxygen). On Earth, life evolved alongside photosynthesis, which provided breathable oxygen for aerobic life. The new results are interesting – they show how breathable oxygen can be created independently of photosynthesis. They could also explain how oxidized rocks on the surface of the planet could have formed.

Leads for space exploration

So, how can we find evidence of life? Mars' current missions provide global mapping of orbit minerals as well as surface information. Recent mobile results include the discovery by Curiosity that organic molecules can live on Mars for a long time. NASA's Mars 2020 mobile mission will cache samples ready for a possible NASA-ESA return mission to Earth, currently scheduled.

However, NASA rovers are designed to dig only five centimeters below the surface. The rover that is part of the ESO-Russia ExoMars 2020 mission we are working on will be able to drill up to two meters below. This is where ultraviolet, cosmic and solar radiation can enter life and harm life, which is our best hope for life on Mars on any planned mission. The ExoMars rover landing site will be selected in November by two current candidates, Mawrth Vallis and Oxia Planum, two former water rich environments.

Water infiltrates Mars.NASA

Although the current strategy is to look for signs of ancient life on Mars, the present life should also be detectable if present. We will have to wait for ExoMars results to see if past or present biomarkers are present and badyze the returned samples in the longer term. Although the rover does not travel to the lake or the water does not infiltrate, there are also traces of brine in other places. It is therefore very likely that they are present on the ExoMars candidate sites.

Beyond current missions, should we specifically target brines? This would certainly provide attractive targets for future missions. The limit of what we can do can be imposed by the difficulty of drilling deep on a distant planet. Drilling up to 1.5 km below the surface to sample the lake would be a large-scale effort that would exceed the capabilities of current technology. It is therefore best to target the nearest surface brine areas, such as water seepage.

Another obstacle is planetary protection. They state that you should not risk contaminating an area where there could be extraterrestrial life with bacteria from the Earth. However, we hope that all Martian life will be hard enough to populate other regions and that our missions, designed and built according to strict guidelines for global protection, will find it.

The conversation

– The conversation | Rappler.com

Andrew Coates is Professor of Physics and Deputy Director (Solar System) at Mullard Space Science Laboratory, UCL.

This article is republished from The Conversation under a Creative Commons license. Read the original article.