Since then robotics explorers began visiting the Red Planet during the 1960s and 1970s, scientists have wondered about the characteristics of the Martian surface. These included stream channels, valleys, lake beds, 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. Specifically, scientists want to know how long water has flowed on the surface of Mars and whether it was persistent or periodic in nature.
The ultimate goal here is to determine whether rivers, streams, and stagnant bodies of water existed long enough for life to emerge. So far, missions like Curiosity and Persistence have amassed volumes of evidence showing how hundreds of large sinkholes once dotted the Martian landscape.
But according to a new study by an international team of researchers, our current estimates of Martian surface water may be a dramatic underestimate. Based on a meta-analysis of years worth of satellite data, the team argues that ancient lakes may once have been a very common feature on Mars.
The research was led by Joseph Michalksi, Associate Professor in the Department of Earth Sciences and Associate Director of the Laboratory for Space Research (LSR) at the University of Hong Kong (HKU). The new work was published in the journal Nature.
“Not all lakes are created equal”
As Michalski explained in a recent HKU press release, current research has focused on larger bodies of water on Mars, potentially neglecting the many smaller lakes that may have existed there:
“We know of about 500 ancient lakes found on Mars, but almost all of the lakes we know of are larger than 100 km2. But on Earth, 70% of lakes are smaller than this size, and occur in cold environments where glaciers have retreated. These small-sized lakes are difficult to detect on Mars with satellite remote sensing, but many small lakes probably existed. It is likely that at least 70% of Martian lakes have yet to be discovered.”
Lake beds are currently one of the main targets for robotic explorers on Mars because ancient lakes would have all the ingredients for microbial light – including water, nutrients and energy sources such as light (for photosynthesis).
Today, the lakes of these ancient water bodies contain sedimentary deposits rich in minerals and iron magnesium/clay carbonates, as well as sulfates, silica, and chlorides. These deposits could potentially contain preserved evidence of ancient atmospheric and climatic conditions on Mars.
But as they point out in the paper, most known Martian lakes date back to the Noachian period (about 4.1 to 3.7 billion years ago) and lasted only 1,000 to 1 million years. In geological terms, this is a relatively short period of time and represents a tiny fraction of the Noahic 400 million year timeline.
This could mean that ancient Mars was also cold and dry and that flowing water was episodic and short-lived. Because of the lower gravity and fine-grained soil of Mars, the team also thought that lakes on Mars would be murky, making it difficult for light to reach very deep and presenting challenges for photosynthesis.
As a result, Michalski and his colleagues argue that large, ancient, environmentally diverse lakes would be a much more promising target for future exploration.
“Not all lakes are created equal,” Michalski said. “In other words, 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 favorable for the formation of of simple life”.
However, there is also evidence that lakes existed on Mars during more recent geological periods but left fewer traces. These include paleolakes in the Hesperian period (3-3.7 billion years ago) and shallow marshy lakes during the Amazonian (less than 3 billion years ago).
These features will be similar to those on Earth, where similar cold conditions exist, and will likely resemble shallow lakes found in drier regions (Hesperia) and thermoclasts (marsh sanctuaries) that occur when permafrost thaws (Amazonia ).
David Baker is an ecologist at HKU’s School of Biological Sciences and co-author of the paper, who is well versed in the microbial systems in Earth’s lakes. As he summarized, Earth analogues could help expand the search for life on Mars by allowing scientists to look in more diverse environments:
“Earth hosts 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 to detect life elsewhere here at home. Most of these tools aim to detect remains and remnants of microbial life.’
This research reinforces ESA’s recently released mineral map of Mars, which showed how hydrous minerals (those formed in the presence of water) are ubiquitous on the surface.
It could also help inform future robotic missions, including ESA’s Rosalind Franklin rover, which is currently scheduled to launch by 2028. China’s first Mars lander and rover mission, Tianwen-1 and Zhuronglanded on May 14, 2022 and is currently exploring the plains of Utopia Planitia.
This region was once the site of an ocean that covered most of the northern hemisphere and likely contains mineralogical and chemical evidence of how and when Mars changed from a warmer, wetter planet to what we see today.
The Persistence The rover is currently collecting and storing samples that will be retrieved by an ESA-NASA sample return mission in the coming years. This will be the first time samples from Mars have been returned for comprehensive analysis that can only be carried out in laboratories on Earth.
China is planning a similar sample return mission that could be sent to a Hesperian or Amazonian lake and will likely take place by the end of the decade. These and other missions will also pave the way for crewed missions, which NASA and China plan to carry out by the early 2030s.
These missions would land in areas that have accessible water, which could double as a site for potential research. If there really was life on Mars billions of years ago (or there still is today), the evidence won’t remain elusive for much longer!
This article was originally published on Universe today with Matt Williams. Read the original article here.