Mars: new research challenges Existence of liquid water lake under the planet’s south pole

Recent studies have cast doubt on the presence of a lake of liquid water beneath the ice cap at Mars’ south pole, a discovery that initially raised hopes of finding microbial life on the Red Planet.

In 2018, the European Space Agency’s Mars Express satellite detected strong radar reflections that indicated a 12-mile-long lake lay beneath the surface of Mars. However, new research from Cornell University offers a less dramatic but comprehensive explanation for these radar signals, suggesting they may be due to natural radar wave interference rather than liquid water.

Research into the radar reflections

The initial excitement came from radar data collected by the Mars Express satellite, which revealed bright reflections from beneath the south polar ice cap, similar to those observed at subglacial lakes on Earth. These reflections led scientists to hypothesize the existence of a liquid water lake, which may harbor microbial life.

In support of this hypothesis, researchers from the University of Cambridge found patterns in the surface ice consistent with a subglacial lake. However, recent simulations conducted by Cornell researchers suggest that small variations in the composition and thickness of the ice layers could produce similar radar reflections without the presence of liquid water.

Daniel Lalich, a research associate at the Cornell Center for Astrophysics and Planetary Science and lead author of the new study, argues that the radar signals can be explained by constructive interference of radar waves. “I can’t say it’s impossible that there is liquid water down there, but we show that there are much simpler ways to get the same observation without having to stretch so far, using mechanisms and materials that we already know about.” that they exist there.”

“But by random chance you can create the same observed signal on the radar,” Lalich said.

It is known to occur at the poles of Mars, causing the composition and spacing of the ice layers to vary. The results showed that the observed bright reflections could be caused by these natural variations in the ice.

Lalich explains: ‘Only by random chance can you create the same observed signal on the radar. This is the first time we have a hypothesis that explains the entire population of observations under the ice sheet, without having to introduce anything unique or strange. “

The new findings

The new research provides a detailed and more realistic model to explain the bright radar reflections that were initially thought to indicate liquid water. By simulating different layering scenarios, the team showed that small variations in ice composition and layer thickness can cause radar waves to constructively interfere, amplifying their reflections. Although these reflections are similar to those produced by liquid water, they do not necessarily indicate its presence.

Lalich’s study, titled “Small variations in ice composition and layer thickness explain bright reflections under Mars’ polar cap without liquid water,” published in Scientific progress, outlines how the bright radar signals could be produced by known materials and conditions on Mars. “The idea that there was liquid water even remotely on the surface would have been very exciting,” Lalich said. “I just don’t think it’s there.”

Implications for the search for life on Mars

The potential existence of liquid water on Mars is a tantalizing prospect because it raises the possibility of microbial life. While robotic explorers like NASA’s Perseverance rover have provided extensive evidence of ancient water flows on the surface of Mars, current conditions at the poles make the existence of liquid water unlikely. The temperature and pressure on Mars differ significantly from those on Earth, complicating the possibility of liquid water beneath the ice caps.

Nevertheless, the search for life on Mars continues. Scientists are exploring other regions and using advanced technologies to detect signs of past or current life. The new research from Cornell underlines the importance of simpler explanations and thoroughly testing hypotheses before drawing a conclusion about the existence of liquid water. Lalich’s findings suggest that bright radar reflections could be caused by natural ice variations, rather than requiring liquid water.

The Cornell study has sparked a debate within the scientific community, with some researchers expressing skepticism. “Scientists from Cambridge said they had not seen the new research, but said the unusual patterns they found on the surface would not be explained by radar interference,” said a statement from the Cambridge team.

While this new insight may reduce the chances of finding liquid water at Mars’ south pole, it does not detract from the importance of continued exploration. Robotic missions and future human explorers will still play a crucial role in unraveling Mars’ secrets and assessing its habitability. For example, the Perseverance rover is currently exploring an ancient river delta in the Jezero Crater, which could yield valuable clues about the planet’s watery past and its potential to support life.

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