At least 70% of martian lakes are yet to be discovered. Mars' missing lakes could provide valuable information about past climates as well.
Throughout Earth, there are lakes, rivers, and groundwater fed by rainfall, snowmelt, and rivers. A lake’s geologic record is also important for understanding past climates. Despite Mars being a frozen desert today, scientists have found evidence of ancient lakes on the red planet that existed billions of years ago. These ancient lakes could provide information about life and climate conditions on Mars during these periods. Using years of satellite data that suggest ancient lakes on Mars, Dr. Joseph Michalski, a geologist at Hong Kong University’s Department of Earth Sciences (HKU), suggested that the number of ancient Martian lakes may have been drastically underestimated by scientists.
Recent research by Michalski and colleagues describes a global analysis of ancient Martian lakes in Nature Astronomy. It is believed that about 500 ancient lakes were deposited on Mars, but the vast majority are greater than 100 km2. Compared to this, 70% of Earth’s lakes are smaller, most of them in cold environments where glaciers have receded. By satellite remote sensing, it is difficult to identify these small lakes on Mars, but they probably existed there. Scientists monitor small lakes on Earth to understand how climate change affects the world. At least 70% of martian lakes are yet to be discovered. Mars’ missing lakes could provide valuable information about past climates as well.
Most of the known Martian lakes were formed 3,500 to 4,000 million years ago, but each lake likely existed for only a short period of time (10,000 to 100,000 years). As a result, ancient Mars was also mostly cold and dry, with periodic warmings. According to Michalski, “As a result of the lower gravity on Mars and the fine-grained soil, lakes on Mars would have been very murky, and light might not have penetrated very deeply, further complicating the possibility of photosynthetic life on Mars.”
Besides water, lakes contain nutrients, energy sources, and light for photosynthesis, which can support microbial life. Hence, NASA’s Perseverance rover, currently on Mars, targets lakes for astrobiological exploration. Michalski cautions, however, that not all lakes are created equal. Therefore, some Martian lakes could have been more conducive to the formation of simple life than others because some of them were large, deep, and long-lived and had a wide variety of environmental conditions, such as hydrothermal systems. It may make sense, then, to explore large, ancient, environmentally diverse lakes in the future.
It is possible to compare the environment on Earth to other planets in many ways. We can design tools to detect life elsewhere right here at home by observing the harsh terrain of Svalbard and the depths of Mono Lake, as an example. In many cases, these tools are used to detect the remains and residues of microorganisms,” says Dr. David BAKER, an ecologist at the HKU School of Biological Sciences who is well versed in the Earth’s microbial systems in lakes.
Earlier this year, China successfully landed its first Mars lander, Zhurong. Scientists are currently exploring former climate change sites on Utopia Planitia with Zhurong. In addition, China plans to return samples from one of these lakes at the end of this decade.
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