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Wednesday, October 27, 2021

What the discovery of liquid water on red planet Mars means

In this Indian Express Exclusive, Dr Amitabha Ghosh explains what the discovery of liquid water on Mars means — for scientists, exploration missions, the human race, and for the future attempts to colonise the Red Planet.

Written by Amitabha Ghosh |
Updated: December 26, 2015 12:11:06 am
Dark, narrow streaks on Martian slopes such as these at Hale Crater are inferred to be formed by seasonal flow of water on contemporary Mars. The streaks, called “recurring slope lineae” or RSL, are roughly the length of a football field. The imaging and topographical information in this processed, false-colour view come from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter. (Source: NASA) Dark, narrow streaks on Martian slopes such as these at Hale Crater are inferred to be formed by seasonal flow of water on contemporary Mars. The streaks, called “recurring slope lineae” or RSL, are roughly the length of a football field. The imaging and topographical information in this processed, false-colour view come from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter. (Source: NASA)

The discovery of liquid water on Mars marks a major milestone in Martian Science. Barely a couple of decades ago, Mars was believed to be a dry and desiccated planet that once had flowing water and a dense atmosphere. However, Mars lost its atmosphere 4 billion years ago — and with it, the atmospheric pressure on Mars was reduced to less than a tenth of the atmospheric pressure on Earth, making water chemically unstable on the surface. Thus, liquid water is not stable on the Martian surface at present — water can be there either as ice or as water vapour.

The story of water on Mars unfolded over the last 20 years. When I worked on the Mars Pathfinder Mission in 1997, Mars was widely perceived by the scientific community to be devoid of water. In fact, there was a near consensus that the surface of Mars was composed of basaltic lava flows. I still remember the first analysis of a Martian rock ever, by the Mars Pathfinder Mission, revealed the composition to be different from basalt. The composition was andesitic — I had crunched the numbers, and had stayed up the night almost convinced that I was making a mistake. In science, there are usually no Eureka moments — instead there is an overall feeling that the observation does not make sense, i.e., it does not conform to existing wisdom and hence, might not be right.

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In a similar fashion, observations from Mars by a flotilla of spacecraft: orbiters, landers and rovers, over a couple of decades, have completely rewritten what we know about Mars today, including what we know about water on Mars! The year was 2002: Mars Odyssey, a NASA orbiter, had released maps showing an abundance of hydrogen around the Martian Poles. The hydrogen could potentially be in the form of water — but that was just one hypothesis with competing hypotheses stating that the hydrogen could be present in a form other than water. In five years, NASA launched the Mars Phoenix mission, to specifically verify if hydrogen present at the Martian Poles was indeed water ice. Phoenix landed on the Martian North Pole in May 2008, and survived for about 150 days. The robotic arms of Phoenix scooped soil and ice from the surface, heated the material in eight ovens, and measured the composition of the gases with a mass spectrometer. As we discovered, this act is not as simple when you are remotely operating a spacecraft in extreme cold about 200 million miles away. The Phoenix mission established conclusively that the initial discovery of hydrogen by Mars Odyssey in 2002 was indeed water ice. Hence, for the first time in the history of Mars, NASA could map out huge deposits of ice, largely concentrated around the Poles.

The discovery of liquid water is equally, if not more significant, than the discovery of ice. The discovery of liquid water below the subsurface makes a human mission logistically easier and cheaper, enhances chances of life on Mars, and provides a way to generate rocket fuel on Mars.

Imagine travelling to New York for six months. Imagine having to carry all the water that you would use. Now imagine travelling to Mars, or about 20,000 times the distance to New York, for 3 years, and having to carry all the water required from Earth. Imagine how much water would be required to be transported over 200 million miles! If the source of the liquid water in Monday’s announcement is not atmospheric but subsurface, if there are sizeable reserves of water under the ground, if this water can be extracted in a cost effective manner, we might have an answer to the water problem for potential visitors for Earth. Availability of water on Mars makes the journey logistically easier and significantly cheaper.

The discovery of water on Mars is significant because life on Earth has been associated with water. There is a very important qualifier: life on Earth is associated with water, but water on Earth is not necessarily associated with life. Water on Mars does not necessarily imply that life exists on Mars — but nevertheless, it does increase the possibility of life. Life on Mars, assuming that it mimics life on Earth, would presumably need a host of factors to evolve and survive: like protection from radiation.

Last but not the least, the largest cost of interplanetary travel is the cost of escaping Earth’s gravity and the gravity of Mars. The discovery of water on Mars can help pave the way for efficient conversion of the liquid water into oxygen that can be used as rocket fuel for the return trip. In fact, in the next Mars Rover Mission to be launched in 2020, NASA will test out the first experiment that will try to separate oxygen from water on Mars — this technology in future could be used to generate oxygen from Martian water. This oxygen could be used for rocket fuel or for use by humans — again causing the cost and complexity of a human mission to drop very significantly.

Will humans ever live on Mars? Of course, they will. A hundred years ago, when Roald Amundsen and Robert Scott raced to reach the South Pole, the South Pole was perceived as a treacherous and inhospitable frontier. Today, McMurdo Station in Antarctica supports more than 1,000 researchers, who live in controlled environments throughout the year. In Mars, there is no reason humans cannot live in temperature- and pressure-controlled chambers that are shielded from radiation. The key will be to find resources on Mars that can be used to support humans during their temporary stay there. The discovery of liquid water, perhaps, is a small step towards this broader goal.

Dr Ghosh leads Rover Operations on Opportunity Rover as Chair of the Science Operations Working Group of the NASA Mars Exploration Rover Mission. Opportunity has been traversing Mars for the last 11 years.

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