Sunday, September 25, 2022

Scientists might have dramatically underestimated the number of ancient Martian lakes

The results describe a global analysis of ancient Martian lakes.

Even though Mars is currently a frozen desert, scientists have found evidence of ancient lakes that existed there billions of years ago. These ancient lakes may have preserved information about the red planet’s old temperature and life.

Dr. Joseph MICHALSKI, a geologist at The University of Hong Kong (HKU), said that scientists may have vastly overestimated the amount of ancient Martian lakes that once existed through a meta-analysis of years of satellite data that reveals evidence for lakes on Mars.

Michalski said, “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.”

Scientists monitor these small lakes on Earth to understand climate change better. The missing small Martian lakes may hold vital clues to previous climates.

The most recent study notes that most Martian lakes dated to 3,500 and 4,000 million years ago but that each lake may have only existed for a minimal amount of time (10,000–100,000 years). This indicates that while ancient Mars was probably largely cold and dry, it warmed episodically for short periods.

Michalski added, “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.”

Water, nutrients, and energy sources for potential microbial life, including light for photosynthesis, are all present in lakes. Therefore, lakes are the primary areas that Mars Rovers, like NASA’s Perseverance rover, which is currently on Mars, are exploring for astrobiological purposes.

But, not all lakes are created equal. Some lakes would be more interesting for microbial life than others because some of the lakes were large, deep, long-lived, and had a wide range of environments, such as hydrothermal systems that could have been conducive to the formation of a simple life. From this point of view, it might make sense to target large, ancient, environmentally diverse lakes for future exploration.

Dr. David BAKER, an ecologist at HKU School of Biological Sciences who is well-informed about the Earth’s microbial systems in lakes, said“Earth is host to many environments that can serve as analogs to other planets. From the harsh terrain of Svalbard to the depths of Mono Lake – we can determine how to design tools for detecting life elsewhere right here at home. Most of those tools are aimed at detecting the remains and residues of microbial life.”

Journal Reference:

  1. Michalski, J.R., Goudge, T.A., Crowe, S.A., et al. Geological diversity and microbiological potential of lakes on Mars. Nat Astron (2022). DOI: 10.1038/s41550-022-01743-7
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