Lakes are bodies of water fed by precipitation, melting snow, rivers and groundwater, through which the Earth teems with life. The lakes also contain critical geological records of past climates. Although Mars is a frozen wasteland today, scientists have shown that Mars contains evidence of ancient lakes that existed billions of years ago, which may contain evidence of life and ancient climatic conditions on the planet. red planet. Through a meta-analysis of years of satellite data showing evidence of lakes on Mars, Dr. Joseph MICHALSKI, a geologist in the Department of Earth Sciences at the University of Hong Kong (HKU) proposed that scientists have significantly underestimated the number of ancient Martian lakes that once existed.
Michalski and the international team recently published their results in natural astronomy, which describe a global analysis of ancient Martian lakes. “We know about 500 ancient lakes deposited on Mars, but almost all the lakes we know are over 100 km2“, explains Michalski. “But on Earth, 70% of lakes are smaller than this size, occurring in cold environments where glaciers have retreated. These small lakes are difficult to identify on Mars by satellite remote sensing, but many small lakes probably existed. 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. Small missing lakes on Mars could also hold critical information about past climates.
The recent paper also reports that most of the known Martian lakes date from 3,500 to 4,000 million years ago, but each of the lakes may have lasted only a geologically short time (10,000 to 100,000 years) during this period. This means that ancient Mars was probably also cold and dry, but warmed episodically for short periods. Michalski adds, “Due to the weaker gravity on Mars and the ubiquitous fine-grained soil, the lakes on Mars would have been very murky and might not have allowed light to penetrate very deep, which could present a challenge to photosynthetic life, if it existed.”
Lakes contain water, nutrients and energy sources for possible microbial life, including light for photosynthesis. Therefore, lakes are prime targets for astrobiological exploration by Mars rovers such as NASA’s Perseverance rover now on Mars. But Michalski warns: “Not all lakes are created equal. In other words, some Martian lakes would be more interesting for microbial life than others because some 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 simple life.” From this perspective, it might make sense to target large, ancient and environmentally diverse lakes for future exploration.
“Earth is home to many environments that can serve as analogs to other planets. From the rugged terrain of Svalbard to the depths of Mono Lake, we can figure out how to design tools to detect life elsewhere, right here at home. Most of these tools are aimed at detecting remnants and residues of microbial life,” said Dr. David BAKER, an ecologist in HKU’s School of Biological Sciences, knowledgeable about Earth’s microbial systems in lakes.
China successfully landed its first lander, Zhurong, on Mars in May this year. Zhurong is currently scouring the plains of Utopia Planitia, exploring mineralogical and chemical clues to recent climate change. China is also planning a sample return mission likely to occur at the end of this decade, which could target one of the interesting lake deposits.
Earth’s lakes emit less methane than previously thought
Joseph R. Michalski et al, Geological diversity and microbiological potential of lakes on Mars, natural astronomy (2022). DOI: 10.1038/s41550-022-01743-7
Provided by the University of Hong Kong
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