Scientists might have dramatically underestimated number of ancient Martian lakes, new study suggests

Though Mars, one of Earth's immediate neighbours, is a frozen desert today, studies have confirmed that it once stored water in lakes - that's billions of years ago. Now, Geologists at the University of Hong Kong (HKU) have proposed that scientists might have dramatically underestimated the number of ancient Martian lakes that once existed.

"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," says Dr Joseph MICHALSKI, a geologist in the Department of Earth Sciences at HKU.

Michalski and his team recently published their findings in Nature Astronomy, which describe a global analysis of ancient Martian lakes. The paper also reports that most known Martian lakes date to a period of 3,500 to 4,000 million years ago, but each of the lakes might have lasted only a geologically short time (10,000 to 100,000 years) during this time span.

Lakes contain water, nutrients and energy sources for possible microbial life, which makes them the top targets for astrobiological exploration. Planetary missions like Perseverance and Curiosity of NASA, ESA's Mars Express orbiter and others are advancing understanding of the Red Planet. Perseverance has collected over a dozen samples from an ancient river delta in the Red Planet's Jezero Crater. The rover is currently investigating the delta’s sedimentary rocks, formed when particles of various sizes settled in the once-watery environment.

China's Mars rover, Zhurong, is also roving the plains of Utopia Planitia, a large plain in the northern hemisphere of Mars, exploring mineralogical and chemical clues to recent climate change.

Michalski says that some Martian 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.