According to a new analysis, the strange bright spots in the radar data collected by the orbiting Mars Express probe could be the result of frozen clay – especially hydrous aluminum silicates or smectite minerals.
“So far, all previous articles could only hint at holes in the lakes argument. We are the first paper to show that other materials are the most likely cause of the observations, ”said planetary scientist Isaac Smith of the Institute of Planetary Sciences and York University in Canada.
“Now our paper offers the first plausible alternative hypothesis and much more likely to explain the MARSIS observations.
The saga began when a team of scientists noticed something strange in the data collected by MARSIS, the radar sounder attached to Mars Express. Under the ice cap at the south pole of Mars was a region that strongly reflected the radar signal. This, the team found out, coincided with a large bag of liquid water in an underground lake.
Follow-up re-search revealed that the region was not alone. Three more really bright spots were found in the MARSIS data. This was huge as it suggested a place where Mars could be habitable for extremophile, chemosynthetic (living on chemical reactions rather than sunlight) microbes. Life.
However, other scientists found a significant problem: Mars is actually too cold, too cold, found a recent paper for large reservoirs of liquid water, even saturated with salt, which lowers the liquid’s freezing point. Which, in turn, has left a huge question mark over the red planet: If the glowing spots aren’t liquid water, then what the hell are they?
After looking at the data, Smith believes that he and his colleagues came up with a very plausible explanation.
“Solid clay frozen at cryogenic temperatures can do the reflections. Our study combined theoretical modeling with laboratory measurements and remote sensing observations,” he said.
“All three agreed that smectites can make the reflections and that smectites are present at the south pole of Mars. It is trifecta: measuring the properties of the material, showing that the properties of the material can explain the observation, and showing that the materials are present at the observation site.
He clarified that smectite clay is present in nearly 50 percent of the Martian surface, with a higher concentration in the southern hemisphere, particularly in the southern highlands. The Curiosity rover has examined smectite deposits in the old dry bed of the lake it is exploring.
There is also ample evidence that liquid water was present at the South Pole of Mars in the past, more than 100 million years ago.
Smith and his team believe that smectite clays may have formed around this time and then buried under the South Pole ice cap. Any ice lost from the clay layer would be replenished from the top ice cap or the frozen soil below, it has remained that way to this day.
The team tested their hypothesis on samples of calcium montmorillonite clay, known to be abundant on Mars, by freezing it at 230 Kelvin (about 43 degrees Celsius or 45 degrees Fahrenheit) and measuring its dielectric permittivity , the property detected by the ground penetrating radar. They found that this is consistent with MARSIS data.
They also used models to estimate the strength of the echo that MARSIS would observe in different scenarios and again found that detection of smectite clay-detection was a plausible explanation for the signal.
Liquid water could still be explained if Mars is heated from within, which might be possible given recent evidence that the planet is geologically and volcanically active, but we don’t know if there is such activity below the South Pole. Smectite clay offers an answer. this does not require an untested factor.
“The lakes under the ice leave more questions unanswered than answered. A simpler answer is that a material that we now know exists at the south pole of Mars explains the anomalous observations better than an exceptional claim on liquid water bodies, ”said Smith.
“”Given the recent work on the subject, find flaws in lake theory, this is like a combination of 1,2,3 hits that drills big holes in the interpretation of the lake and then solves the puzzle. A hit of funny in my opinion.
The research has been published in Geophysical Research Letters.