Perhaps Mars was covered in lakes in the ancient past

Since robotic explorers began visiting the Red Planet during the 1960s and 1970s, scientists have puzzled over the features of Mars’ surface. These included flow channels, valleys, lake basins, and deltas that appear to have formed in the presence of water. Since then, dozens of missions have been sent to Mars to explore its atmosphere, surface, and climate to learn more about its warmer, wetter past. In particular, scientists want to know how long water has flowed on Mars and whether it is permanent or cyclical in nature.

The ultimate goal here is to determine if rivers, streams, and permanent bodies of water have existed long enough for life to appear. So far, like missions Curiosity of And the perseverance I have collected loads of evidence showing how hundreds of large lake beds once dotted the landscape of Mars. But according to a new study by an international team of researchers, our current estimates of surface water on Mars may be significantly understated. Based on a meta-analysis of satellite data over the years, the team argues that ancient lakes may have once been Very common feature on Mars.

The search was led by Dr.. Joseph MichalkiHe is an associate professor in the Department of Earth Sciences and deputy director space research lab (LSR) at Hong Kong University (HKU). He was joined by researchers from Canadian Institute for Advanced Research (Sevar), and Residential Planetary Systems Center at UT Austin, University of British Columbia (UBC), Museum of Natural History, Brown University and Georgetown. The paper describing their findings is titled “Geological diversity and microbiological potential of lakes on MarsRecently appeared in the magazine temper nature.

Example of a large lake hosted by a crater on Mars (left) and a small lake hosted by permafrost (right). Credit: ESA/JPL/NASA/ASU/MSSS

As explained by Michalski in a recent HKU press releasethe current research has focused on larger bodies of water on Mars, which may neglect many of the smaller lakes that may have been there:

“We know of approximately 500 ancient lakes deposited on Mars, but nearly all of the lakes we know are larger than 100 km.2. But on Earth, 70% of lakes are smaller than this size, and they occur in cold environments where glaciers have retreated. These small lakes on Mars are difficult to identify by satellite remote sensing, but there are likely many small lakes. It is possible that at least 70% of the lakes on Mars have yet to be discovered.”

Lakebeds are currently one of the main targets of robotic explorers on Mars because ancient lakes would have all the components of microbial light – including water, nutrients, and energy sources such as light (for photosynthesis). Today, the lake basins of these ancient bodies of water contain mineral- and carbonate-rich sedimentary deposits of iron/magnesium clay, as well as sulfates, silica, and chlorides. These deposits could contain preserved evidence that would attest to ancient atmospheric and climatic conditions on Mars.

But as they point out in the paper, most of the known Martian lakes date from the Noach period (about 4.1 to 3.7 billion years ago) and only lasted 1,000 to 1 million years. Geologically speaking, this is a relatively short period of time and represents a small part of the 400 million years of the Noachian timeline. This could mean that ancient Mars was also cold and dry, and that the flowing waters were occasional and short-lived. Given Mars’ lower gravity and fine-grained soil, the team also hypothesized that lakes on Mars would be opaque, making it difficult for light to reach great depths and posing challenges to photosynthesis.

As a result, Michalsky and colleagues argue that large, ancient, and ecologically diverse lakes will constitute a promising target for future exploration. “Not all lakes are created equal,” Michalsky said. “In other words, some Martian lakes may have been more exciting 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 would have been favorable to the formation of simple life.”

Bingwalite crater lake in Canada is a modern example of a crater-hosted lake on Earth that resembles ancient crater lakes on Mars. Credit: Google Earth

However, there is also evidence that lakes existed on Mars during recent geological periods but left fewer traces. These include the ancient lakes of the Hesperian period (3-3.7 billion years ago) and shallow swampy lakes through the Amazon (less than 3 billion years ago). These features may be similar to those on Earth where similar cold conditions exist and likely resemble the shallow lakes found in the driest regions (Hesperian) and chromoclasts (the swamp hollies) that occur during thaw permafrost (Amazon).

Dr. David Baker is an ecologist at the Hong Kong College of Biological Sciences and a co-author of the paper who is well versed in the microbial systems of Earth’s lakes. As he summarized, Earth isotopes could help expand the search for life on Mars by allowing scientists to search in more diverse environments:

“Earth hosts many environments that could serve as analogues for other planets. From the harsh terrain of Svalbard to the depths of Mono Lake – we can determine how to design tools to detect life elsewhere here at home. Most of these tools are aimed at discovering the remains and remains of microbial life,”

This research supports the ESA’s recently released mineral map of Mars, which showed how hydrated minerals (those that form in the presence of water) are ubiquitous on the surface. It could also help inform future robotic missions, which include ESA Rosalind Franklin rover, which is currently scheduled to launch by 2028. The first Chinese rover landing and landing mission to Mars, Tianwen-1 And the Zuronglanded on May 14, 2022, and is currently exploring the plains of Utopia Planetia.

Mineral map of Mars showing patches formed in the presence of water. Credit: ESA

This region was once the site of the ocean that covers most of the Northern Hemisphere and likely contains mineral and chemical clues about how and when Mars transitioned from a warmer, wetter planet to what we see today. The perseverance The rover is currently collecting and buffering samples that will be retrieved by a European Space Agency and NASA sample return mission in the coming years. This will be the first time samples have been returned from Mars for a comprehensive analysis that can only happen in laboratories on Earth.

China is planning a mission to return a similar sample that could be sent to Lake Hesperian or the Amazon, likely to occur by the end of the decade. These and other missions will also pave the way for manned missions, which NASA and China plan to undertake by the early 2030s. These missions will land in accessible areas of the water, which could double as a potential research site. If there really was life on Mars billions of years ago (or still exists today), the evidence won’t stay out of reach for much longer!

In-depth reading: HKUAnd the temper nature