Missing Ancient Martian Lakes in the Data

Sep 21, 2022 | Daily Space, Mars

IMAGE: An example of a large, impact crater-hosted lake on Mars (a) and a small, permafrost-hosted lake on Mars. Both images show elevation data from the MOLA (Mars Orbiter Laser Altimeter) and HRSC (High Resolution Stereo Camera) instruments draped onto images from THEMIS (a) and CTX (b). CREDIT: ESA/JPL/NASA/ASU/MSSS

While JWST seems primed to help understand Mars’s current atmospheric conditions, a new paper published in Nature Astronomy with lead author Joseph R. Michalski contends that we are vastly underestimating just how many lakes there were back in Mars’s more watery period.

Estimating the number of lakes on Mars is important to understanding how the planet changed over millennia on both large and small scales. Michalski explains: We know of approximately 500 ancient lakes deposited on Mars, but nearly all the lakes we know about are larger than 100 km2. But on Earth, 70% of the lakes are smaller than this size, occurring in cold environments where glaciers have retreated. These small-sized lakes are difficult to identify on Mars by satellite remote sensing, but many small lakes probably did exist. It is likely that at least 70% of Martian lakes have yet to be discovered.

Additionally, all these lakes likely only lasted a geologically brief time – about 10,000 to 100,000 years. And this new paper dates those lakes back to 3.5 to 4 million years ago, which gives a pretty narrow window for the development of life. On top of that issue, Michalski notes: Because of the lower gravity on Mars and the pervasive, fine-grained soil, lakes on Mars would have been very murky and might not have allowed light to penetrate very deeply, which could present a challenge to photosynthetic life, if it existed.

None of this means we should give up hope of finding that evidence. We have managed to find life in the wildest of environments here on Earth, including deep underground and in sulfur ponds. Mars isn’t outside the realm of possibility, but we’re going to have to keep searching, and we may need to search for those smaller lakes, too.

More Information

The University of Hong Kong press release

Geological diversity and microbiological potential of lakes on Mars,” Joseph R. Michalski et al., 2022 September 15, Nature Astronomy

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