Misled by a Mars Mirage: Hope for Present-Day Martian Groundwater Dries Up

Mars South Pole and Beyond

A view of Mars’ south pole. Research led by The University of Texas at Austin found that a 2018 discovery of liquid water under the Red Planet’s south polar cap is most likely just radar reflecting from volcanic rock. Credit: ESA/DLR/FU Berlin

Liquid water previously detected under Mars’ ice-covered south pole is probably just a dusty mirage, according to a new study of the red planet led by researchers at The University of Texas at Austin.

Scientists in 2018 had thought they were looking at liquid water when they saw bright radar reflections under the polar cap. However, the new study published today (January 24, 2022) in the journal Geophysical Research Letters found that the reflections matched those of volcanic plains found all over the red planet’s surface. 

The researchers think their conclusion — volcanic rock buried under ice — is a more plausible explanation for the 2018 discovery, which was already in question after scientists calculated the unlikely conditions needed to keep water in a liquid state at Mars’ cold, arid south pole.

“For water to be sustained this close to the surface, you need both a very salty environment and a strong, locally generated heat source, but that doesn’t match what we know of this region,” said the study’s lead author, Cyril Grima, a planetary scientist at the University of Texas Institute for Geophysics (UTIG). 

The south polar mirage dissolved when Grima added an imaginary global ice sheet across a radar map of Mars. The imaginary ice showed how Mars’ terrains would appear when looked at through a mile of ice, allowing scientists to compare features across the entire planet with those under the polar cap.

Mars Globe With Ice

A radar map of Mars as seen through a mile of ice. UT Austin planetary scientist, Cyril Grima, built a computer model to cover the Red Planet in ice and observed how it changed the radar data. This caused volcanic plains (seen in red) to reflect radar in a manner that resembled liquid water. The finding challenges a 2018 study that appeared to find liquid water under Mars’ south polar cap. Credit: Cyril Grima

Grima noticed bright reflections, just like those seen in the south pole but scattered across all latitudes. In as many as could be confirmed, they matched the location of volcanic plains.

On Earth, iron-rich lava flows can leave behind rocks that reflect radar in a similar way. Other possibilities include mineral deposits in dried riverbeds. Either way, Grima said, figuring out what they are could answer important questions about Mars’ history.

Although there may not be liquid water trapped under the southern polar cap, there is plenty of water ice on Mars, including in the thick polar caps. In fact, the new study hints at Mars’ wetter past. 

Isaac Smith, a Mars geophysicist at York University, believes the bright radar signatures are a kind of clay made when rock erodes in water. In 2021, Smith, who was not part of either study, found that Earth-based clays reflected radar brightly, just like the bright spots in the 2018 south pole study.

“I think the beauty of Grima’s finding is that while it knocks down the idea there might be liquid water under the planet’s south pole today, it also gives us really precise places to go look for evidence of ancient lakes and riverbeds and test hypotheses about the wider drying out of Mars’ climate over billions of years,” he said.

Grima’s map is based on three years of data from MARSIS, a radar instrument launched in 2005 aboard the European Space Agency’s Mars Express that has accumulated tremendous amounts of information about Mars. Grima and co-author Jérémie Mouginot, a research scientist at the Institute of Environmental Geosciences in Grenoble, France, plan to dig further into the data to see what else MARSIS can turn up about Mars. 

For Smith, the study is a sobering lesson on the scientific process that is as relevant to Earth as it is to Mars.

“Science isn’t foolproof on the first try,” said Smith, who is an alumnus of the Jackson School of Geosciences at UT Austin. “That’s especially true in planetary science where we’re looking at places no one’s ever visited and relying on instruments that sense everything remotely.”

Grima and Smith are now working on proposed missions to find water on Mars with radar, both as a resource for future human landing sites and to search for signs of past life.

Reference: “The Basal Detectability of an Ice-Covered Mars by MARSIS” by C. Grima, J. Mouginot, W. Kofman, A. Hérique and P. Beck, 24 January 2022, Geophysical Research Letters.
DOI: 10.1029/2021GL096518

The current study was partially funded by NASA and CNES, the French national space agency. The Institute of Environmental Geosciences (Institut des Géosciences de l’Environnement) is a joint research unit of the French National Centre for Scientific Research, Université Grenoble Alpes and other institutions in France. UTIG is a research unit of the UT Jackson School of Geosciences.

3 Comments on "Misled by a Mars Mirage: Hope for Present-Day Martian Groundwater Dries Up"

  1. Very Interesting Science.

    Well done.

    However, here are some thoughts for consideration.

    1. Water and its nature. We are truly blessed to have a planet earth with 75% water. The temperatures within which it can become a solid, and liquid and gas is well known. It’s behaviour between zero and 4 degrees celsius haas also been studied. The question is can Water exist in other states which we are not yet fully aware of. Say fifth state of water and higher states in different circumstances at both ends of the temperature and pressure spectrum. Important to understand, as all carbon based life forms are not water independent.

    2. The critical importaance of being able to gather data, analysing the same and drawing inferences based on data gathered , where multiple interpretations are possible, should make all us humans humble. Interpretation of data and drawing conclusions is the difficut task in a scenario where multiple interpretations are possible.

    3. Optical illusions are not new. They are the result of the human mind with life , and conscious thinking facuties intact , but impaired, aspiring for a much sought after item like water in a desert. We as a species are highly dependent on the fives senses and use of intuition and higher sense perceptions is rare and labelled as pseudo-science.

    4. Developing the faculties we all possess, to use such inherent human capbilities is very much possible. This requires training fron childhood in various methods which will help open our eye of insight (Intuition) and other higher senses.

    5. Coming back to the article in question. The ability of the human mind to distinguish between what is real and and what is an optical illusion, using the five senses alone limits our ability to see reality.

    6. The chemical composition of water is known and detection of hydrogen and oxygen presence from the shining southern polar cap, where if water exists and is not a optical illusion, can be determined, by determining if whater actually exists in the southern ploar cap in Mars.The use of virtual ice is a praiseworthy strategy. However, it needs to be confirmed with actual evidence onthe ground.

    6. On a lighter note, the neighbouring planet Earth, also has a southern pole as well as northern pole, where I suspect water does exist in solid state, and it is rumoured that a gentleman by the name of Santa Claus and his elfs live and have factory producing toys for kids to distrubute all across the globe. Hope the Factory has got clearance from OSHA and is non polluting. I dont know if the Supply Chain Problems we faced in the last couple of years affected Sants Toy Factory.

    7.Seriously, data from the two poless on the planet we inhabit (earth) would be usefl. If similar data can be gathered from various databases, and then compared with the similar data from the Martian Surface, we would have at least one planet we know about, to benchmark the information from data gathered from Mars.

    Standalone data without Comparative data is iffy. We learnt this in Buisness school from studying competitive analysis.

    Views expressed are personal and not binding on anyone..

  2. The sediments on Mars are billions of years old. They also thought that hematite seen from space was an indication of liquid water on or close to the surface….even though hematite does not form in water. It is derived from the dehydration of hydrous oxides that do form in water.

  3. I fail to understand this desire to live on Mars. Why can’t we just use all the science and money here on earth to fix this place, live in peace in a sustainable manner. I remember Sputnik, John Glenn, Neil Armstrong. Yes it was great science, and made us proud. But we’re now learning that we need to take better care of where we are before we go off polluting some other planet.

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