[ad_1]
A web of strange features discovered underground at the south pole of Mars may not be liquid saltwater lakes after all.
The strange shiny specks in radar data collected by the orbiting Mars Express probe could result from frozen clay – in particular, hydrated aluminum silicates or smectite minerals, according to a new analysis.
“To date, all of the previous articles could only suggest holes in the lakes argument. We are the first article to show that another material is the most likely cause of the sightings,” the planetologist said. Isaac Smith of the Planetary Science Institute and York University in Canada.
“Now our article offers the first plausible, and considerably more likely, alternative hypothesis 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 southern polar ice cap of Mars, there was an area that strongly reflected the radar signal. The team discovered that it corresponded to a large pocket of liquid water – an underground lake.
Follow-up research revealed that the region was not alone. Three other really bright spots were found in the MARSIS data. This was huge, as it suggested a place in which Mars could be habitable for extremophilic and chemosynthetic microbial life (living on chemical reactions rather than sunlight).
But other scientists have discovered an important problem: Mars is really very cold. Too cold, according to a recent article, for large reservoirs of liquid water, even saturated with salt, which lowers the freezing point of the liquid. Which, in turn, left a giant question mark on the Red Planet: If the bright spots aren’t liquid water, what the hell are they?
After looking at the data, Smith believes he and his colleagues have come up with a very plausible explanation.
“Solid clays frozen at cryogenic temperatures can make reflections. Our study combined theoretical modeling with laboratory measurements and remote sensing observations,” he said.
“All three agreed that smectites can do the reflections and that smectites are present at the south pole of Mars. This is the winning trifecta: measuring the properties of materials, showing that the properties of materials can explain the observation and demonstrate that the materials are present at the place of observation. “
Smectite clay, he said, is present over nearly 50 percent of the Martian surface, with a higher concentration in the southern hemisphere, especially in the southern highlands. The Curiosity rover has examined smectite deposits in the old dry lake bed it is exploring.
There is also ample evidence for the presence of liquid water at the Martian South Pole in the past, over 100 million years ago.
Smith and his team believe that smectite clays may have formed around this time and were later buried under the South Pole ice cap. Any ice lost from the clay layer would be replenished from the ice cap above or the frozen ground below, so it remains to this day.
The team tested their hypothesis with samples of calcium-montmorillonite clay, known to be abundant on Mars, freezing it at 230 Kelvin (about -43 degrees Celsius or -45 degrees Fahrenheit) and measuring its dielectric permittivity – the property captured by ground penetrating radar. They found it to be consistent with the MARSIS data.
They also used modeling to estimate the echo strength that would be observed by MARSIS in different scenarios, and again found that smectite clay detection was a plausible explanation for the signal.
Liquid water could still be explained if Mars is heated from within – which may be possible, given recent clues that the planet is geologically and volcanically active. But we don’t know that there is such activity under the South Pole. Smectite clay provides a response that does not require an unverified factor.
“Lakes under the ice leave more questions unanswered than answers. A simpler answer is that a material we now know at the south pole of Mars explains anomalous sightings better than an extraordinary demand for masses of liquid water. “said Smith.
“Considering recent work on this subject finding flaws with the lake theory, it sounds like a 1-2-3 punch combination that pits big holes in the interpretation of the lake and then solves the riddle. In my opinion, it’s a knockout. “
The research was published in Geophysical research letters.
[ad_2]
Source link