In 2018 the team of Italian scientists announced to the world Lake on Mars. Using satellite radar data, the team detected the brightest part of the South Pole at a distance of about 20 km, located at a depth of about 1.5 km under ice and dust.
After analysis, they concluded that the bright area was a sub-classic lake filled with liquid water. The discovery raised some fundamental questions.
Is this the only lake on Mars hidden under ice? What is the liquid water like in the extreme cold of the South Pole on Tuesday when the average surface temperature is less than -100 than C?
After receiving additional satellite data, I and my colleagues Three more were discovered Detected in 2018 unique “lakes” near the site and confirmed the presence of liquid water in all four bodies.
How do we find ice-covered lakes on Mars?
Radar Sound is one of the marsis (advanced radar and surface and ionosphere sound recordings of Mars). Eight tools European Space Agency orbits aboard the Mars Express. The spacecraft has been orbiting the Red Planet since December 2003.
Orbiting radar radiates “silps” toward the planet’s surface. These signals are partially reflected by the surface and penetrate somewhat deeper, where they can be absorbed, scattered, or reflected back to the radar. Liquid water reflects radar signals better than many objects, so the body surface of liquid water shines brightly on a radar film.
Earth radar sounders are used to detect sub-classic lakes in Antarctica, Greenland and Canada. Here, a technique called radio-echo sounding (RES) is commonly used to analyze signals.
There are some obvious differences between how radar sound is used on Earth and Mars. Initially, MARSIS operated from an altitude of 250 km to 900 km above the surface, had a 40 m long antenna, and operated at much lower frequencies (1.8–5 MHz) than Earth-based radar sounders.
These differences meant that some work had to be done to modify standard radio-echo sound techniques for use with Marcis’ signals. However, they were able to analyze data from 134 Marcis tracks purchased between 2010 and 2019 with a width of 250 km and a length of 300 km near the South Pole of Mars.
In this area, in 2018 we identified three uniquely bright reefs around the lake we had already “seen”. Then we used the unusual Probability method To ensure that the bright patches actually represent bodies of liquid water.
We also got a very clear picture of the shape and size of the lake discovered in 2018. It is still the largest of the bodies of water, extending 20 km across its narrow axis and 30 km long.
How is the liquid water beneath the Martian ice?
The average surface temperature in our study area is -110 C. The temperature at the bottom of the ice may be slightly warmer, but below the freezing point of pure water.
So, how can bodies of liquid water be here, and let it take so long to find them?
Since the first lake was discovered in 2018, other groups have suggested the area may be Heats up from below By magma within the surface of the planet. However, to date there is no evidence, so we think the highest salt content in water would be an explanation.
Perchlorate salts containing chlorine, oxygen and another element such as magnesium or calcium are ubiquitous in Martian soil. These salts absorb moisture from the atmosphere and liquefy (this process is called “delicacy”), forming hypersaline aqueous solutions (brine), which crystallize at temperatures below the freezing point of pure water. Further, Laboratory tests They show that the solutions formed by the technique can remain liquid for a long time, even after temperatures have dropped below their own freezing points.
So we suggested in our paper that the water in the South Pole sub-classic lakes is “salt”. It is particularly attractive because it has been proven that it can hold such saltwater Adequately dissolved oxygen To support microbial life.
Can conditions be right for life under the snow?
Our findings raise new questions. Is the chemistry of the water in the South Pole sub-classic lakes suitable for life? How does this change our definition of living environment? Was there ever life on Mars?
New experiments and new missions need to be planned to address these questions. In the meantime, we are preparing to continue to obtain Mars data to gather as much evidence as possible from the surface of Mars.
Each new piece of evidence brings us one step further to answer some of the most basic scientific questions about Mars, the solar system, and the universe.