Astronomers would have deduced from radar data from MARSIS that the red planet contains a whole network of underground lakes. Critics keep a close eye on things.
In 2018, a team of Italian astronomers with much fanfare announced that it had discovered a lake of liquid water beneath the Martian ice. Now the same astronomers claim to have found evidence that it is no longer one subglacial; many more saltwater lakes would be hidden under the Martian surface.
Two years ago, the astronomers stumbled upon the underground lake using the MARSIS instrument aboard the Mars Express spacecraft. MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) emits radar pulses that penetrate the surface and the ice sheets of Mars. The instrument then measures how the radio waves propagate and reflect back to the spacecraft. These reflections provide scientists with information about what lies beneath the surface.
Using the data obtained, the team then mapped an area with a very sharp change in the associated radar signal – about a mile below the surface of the ice and about 12 miles sideways. The radar profile of this area was comparable to that of liquid water lakes beneath Earth’s Antarctic and Greenland ice sheets. This led the researchers to suggest that there is a subglacial lake at this location on Mars.
For the current study, the astronomers are going through the two-year-old data again. For this they used better methods than in 2018, the researchers write Nature Astronomy. The analysis showed that there are more pools of liquid salt water under the Martian surface.
The fact that the water is liquid, and not frozen, is due to the fact that the salts magnesium, sodium and calcium have dissolved in the water, causing brine to be formed. Together with the pressure of the overlying ice, this lowers the melting point, keeping the water liquid.
Hot or not?
Yet not everyone reacted enthusiastically about the discovery. For example, Earth and Mars scientist Maarten Kleinhans (Utrecht University) was not very enthusiastic about the news in 2018. “We have known for a long time that there was and is liquid water, and even roughly when and where all that much water from the past is now”, he already said to KIJK at the time.
Perhaps we are once again dealing with a storm in a glass of water.
Sources: Nature Astronomy, Nature, Gizmodo
Beeld: Steve Lee, Univ. Colorado/Jim Bell, Cornell Univ./Mike Wolff, SSI/NASA
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