This ancient mud lake could be the best place to look for life on Mars: ScienceAlert

When it comes to Mars and our ongoing efforts to understand the ancient habitability of this planet, the evidence is still elusive. But scientists have an idea where the evidence might be hiding: in the sediments.

New research shows that an ancient mud lake is a good place to explore.

Where should we look for evidence of life on Mars? It’s not obvious, although regions with lots of sediment are a good starting point.

That’s one reason NASA’s Perseverance rover is in Jezero Crater, the site of an ancient paleo-lake where sediment deposits may be a kilometer away. Deep. But there are many regions rich in sediments.

Where else should scientists look to expand their reach?

“The search for past Martian life depends on locating surface features associated with ancient habitability,” the researchers wrote in their paper.

One region of interest is where massive outflow channels carry material from the southern mountains of Mars into the northern lowlands, east of the Valles Marineris.

Huge amounts of sediments accumulated in these northern lowlands, and this may suggest that this is a good place to explore. But the authors of a new paper say that could be a mistake.

The article is “Exploring the Evidence for Sedimentary Burst Remnants of the Middle Amazonian Aquifer in a Martian Chaotic Terrain.” It was published in Nature Scientific Reportsand the lead author is Alexis Rodriguez, a senior researcher at the Planetary Science Institute.

Instead of studying the area where the sediments are flowing, scientists should focus on the source of the sediments.

“Entering the northern plains for sampling can be uncertain, as distinguishing between aquifer-derived materials and those eroded and transported during channel formation can become a complex task,” Rodriguez said. .

Instead, researchers should focus on the Hydraotes Chaos region, a subregion of Oxia Palus. Hydraotes Chaos may contain an ancient mud lake in the form of plains, and the sediments there may harbor evidence of life.

This is the Oxia Palus quadrangle, one of 30 quadrangle maps that the USGS uses. There are massive, ancient drains in the area that are attracting scientific attention. But a new study says that an area called Hydraotes Chaos, in the yellow box, is a better target because it’s the source of some of the sediment. The authors suggest that this is a promising region to search for evidence of life. (USGS)

“The plains located within Hydraotes Chaos offer a unique look at ancient aquifer materials. These flats, which we believe were formed by mud extruding into a basin directly above their aquifer, provide a more targeted exploration opportunity,” Rodriguez said.

The vast flood channels stretching from the mountains to the lowlands are a region so vast that it is almost impossible to explore. There is also the complex task of distinguishing sediments from different sources in the vast region. The flat pool in Hydraotes Chaos can simplify exploration.

“Unlike vast flood channels with their complex erosion patterns, this discovery simplifies the study of Martian aquifers, reducing the risk of terrestrial sediment acquisition and opening a new window into the geological past of Mars,” Rodriguez said.

This basin is more directly connected to the subsurface of Mars, and if the planet had ever been habitable, its subsurface would likely have remained habitable longer than the surface.

When Mars’ magnetic shield failed about four billion years ago, the surface became an inhospitable place. But simple life could continue underground, given the right conditions.

“Our study focuses on a sedimentary unit within the Hydraotes Chaos, which we interpret as the remains of a mud lake formed by ejecta from a gas-charged mudstone stratigraphy dating back nearly 4 billion years, a time when the surface of Mars was probably “These sediments may contain evidence of life from this or subsequent periods,” Rodriguez said.

“It’s important to remember that the Martian subsurface may have included habitability that lasted throughout the history of life on Earth,” Rodriguez added.

Hydraotes Chaos
This survey figure shows Hydraotes Chaos (white outline), including the location of the proposed mud lake (black arrow). (Rodriguez et al. 2023/NASA)

The surface of Mars and its geology is a puzzle that is not easy to solve, although scientists have made progress. Sometimes this involves deep digging, as in this study. The ancient mud lake is not where life existed, but it is closely related to where it could have existed, if it had existed at all.

Here’s what researchers think happened in this region in Mars’ deep past.

The ancient mud lake had a mudstone aquifer directly beneath the lake. In the mudstone, volcanic activity caused phase segregation, forming huge chambers of mostly liquid water that were several kilometers wide and hundreds of meters deep. The chaotic nature of the Hydraotes Chaos terrain suggests that there are many of them and that they are interconnected. Earth has similar characteristics, but is nowhere near as large.

Hydraotes chaos diagram
This research figure shows some of the details behind the formation of the mud lake. Note the interconnected chambers underground and how igneous intrusion helped push water and sediment into a basin of subsidence that is Mud Lake. (Rodriguez et al. 2023)

But all that water and sediment didn’t stay in the aquifer.

“Initially, the biomolecules could be dispersed in the volume of large cavities filled with groundwater.” Rodriguez said. “As the water was released to the surface and accumulated, the water disappeared, leaving behind sediment residues and potentially high concentrations of biomolecules.”

Potentially high concentrations are a good place to start, and NASA has taken note.

“NASA Ames is considering the Plains as a possible landing site for a mission to search for evidence of biomarkers, specifically lipids. These biomolecules are extremely durable and could last for billions of years on Mars,” co-author Mary Beth Wilhelm of NASA Ames Research Center said.

The region has other interesting features, and they are also pieces of the Martian puzzle. There are widespread mud volcanoes and also diapirs, igneous intrusions of deformable material thrust through the brittle overlying rock. This gives researchers insight into underground processes and structures without having to dig for them.

Mars mud volcanoes
This figure from the study shows how what could be mud volcanoes (orange dots) and diapirs (white dots) are widespread. In both types of features, sediments may have breached the surface. The yellow box highlights the potential landing site. (Rodriguez et al. 2023/NASA)

In addition, the study region includes widespread mud volcanoes and possible diapirs, providing additional windows into subterranean, potentially habitable rocks,” said co-author Jeffrey Kargel, also of NASA AMES.

“A small rover could sample mud lake sediments and these materials at short distances, dramatically increasing the chances of detecting biosignatures.”

The age of the region is also consistent with the goals of Mars exploration and the history of the planet. The plains may only be a billion years old, meaning that no biomolecules would have been on the surface for three or more billion years like some other regions. This increases the chances of finding intact biomolecules, as exposure to the surface would degrade them.

“Our crater counts show that the plains are relatively recent, returning an age of 1 billion years. This age is good news for our search for life. This age is much younger than the age of most Martian aquifer releases dating back to approximately 3.4 billion years ago. So the materials have spent a tremendous amount of time below the surface,” said co-author Berman.

A small rover could visit many of these features without traveling great distances, and that’s always an attractive idea. The farther a rover has to travel, the bigger, more complex and more expensive it usually has to be. In addition, there is a greater risk of damage, breakdown or other problems.

ESA’s upcoming Rosalind Franklin rover will land in Oxia Planum sometime after 2028, but its landing site is far from this region.

There are currently no plans for a mission to Hydraotes Chaos and the ancient mud lake. But the team has targeted a specific landing site for a potential mission in the region.

Periphery of the Lake Mars floodplain
This image shows the region inside the yellow box in the image above. It shows the boundary of the lobe forming part of a constant-elevation contact, which the authors suggest is the lake’s inundation margin. This region is a good place to land because of its proximity to so many features. (Rodriguez et al. 2023/NASA)

Who knows how long or how many missions it will take before we find the evidence we’re looking for. Maybe we never will. But as long as we keep looking, there’s a chance.

The better we understand the planet as a whole, the more we know where to look. This work points to what could be a prime location for research, but we’ll have to wait and see.

This article was originally published by Universe Today. Read the original article.

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