New Mars water map will prove invaluable for future exploration

Science and Exploration

22/08/2022
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A new map of Mars is changing how we think about Earth’s past water and showing where we should land in the future.

This map, showing deposits on Earth, was created over the past decade using ESA’s Mars Express Observatoire pour la Mineralogie, l’Eau, les Glaces et l’Activité (OMEGA) instruments and NASA’s Mars Reconnaissance Orbiter Compact Data from the Reconnaissance Imaging Meticulous Mapping of the Spectrometer for Mars (CRISM) instrument.

Specifically, the map shows the location and abundance of hydrous minerals. These come from rocks that have been chemically altered in the past by the action of water, often transformed into clays and salts.

Global Map of Martian Hydrated Minerals

On Earth, clays are formed when water interacts with rocks, and different conditions produce different types of clays. For example, clay minerals such as smectite and vermiculite are formed when relatively small amounts of water interact with the rock, thus retaining essentially the same chemical elements as the original volcanic rock. In the case of smectite and vermiculite, these elements are iron and magnesium. Rocks can change more when the amount of water is relatively high. Soluble elements tend to be carried away, leaving behind aluminum-rich clays such as kaolin.

The biggest surprise was the ubiquity of these minerals. A decade ago, planetary scientists knew about 1,000 outcrops on Mars. This makes them interesting geological wonders. However, the new map turns the tables, revealing hundreds of thousands of such regions in the oldest parts of the planet.

“This work has now established that when you study ancient topography in detail, it is actually a strange thing not to see these minerals,” said the Institute for Astrophysics Space Research (IAS) and the Laboratory for Astrophysics in Marseilles (LAM) Said John Carter of Paris-Saclay University and Aix-Marseille University in France.

This is a paradigm shift in our understanding of the history of the Red Planet. Judging by the small amounts of water-based minerals we previously knew to exist, water may be limited in scope and duration. Now, there is no doubt that water has played a huge role in shaping the geology around the planet.

Now, the big question is whether the water persists or is limited to shorter, more intense bouts. While a definitive answer has not yet been provided, the new results undoubtedly give researchers a better tool to seek answers.

“I think we collectively oversimplified Mars,” John said. He explained that planetary scientists tend to think that only a few clay minerals on Mars were produced during wet periods, and then as the water dries up, the entire planet produces salt.

This new map suggests it’s more complicated than previously thought. While many Martian salts may have formed later than clays, the map shows many exceptions where salts and clays were intimately mixed, and some salts are thought to be older than some clays.

“The evolution from a lot of water to no water is not as clear-cut as we thought, and water doesn’t stop overnight. We see a wide variety of geological contexts, so there is no single process or simple timeline that can explain Martian mineralogy The evolution of . This is the first result of our study. The second is that if you exclude life processes on Earth, Mars exhibits diverse mineralogy in geological settings, just like Earth does,” he said.

In other words, the more we look closely, the more complex Mars’ past becomes.

Jezero crater rich in minerals of water

OMEGA and CRISM instruments are well suited for this investigation. Their datasets are highly complementary, operate in the same wavelength range, and are sensitive to the same minerals. CRISM uniquely provides high-resolution spectral imaging of the surface (down to 15m/pixel) for highly localized Martian patches, making it best suited for mapping small regions of interest, such as rover landing sites. For example, the map shows that the Jezero crater, currently being explored by NASA’s 2020 Perseverance rover, displays a rich variety of hydrated minerals.

On the other hand, Omega provides global coverage of Mars with higher spectral resolution and better signal-to-noise ratio. This makes it more suitable for global and regional mapping and to distinguish different alteration minerals.

The results are published in two papers by John, Lucie Riu and colleagues. Lucie worked at the Japan Aerospace Exploration Agency (JAXA) Institute for Space and Astronautical Sciences (ISAS) in Sagamihara, Japan, where the work was partially completed, but is now an ESA researcher at ESA’s European Space Astronomy Centre (ESAC) Madrid.

With basic testing in place, Lucy decided to take the next step, quantifying the amount of minerals present. “If we know where and what percentage of each mineral is present, it can give us a better understanding of how these minerals are formed,” she said.

The work also gives mission planners some good candidates for future landing sites — for two reasons. First, water-based minerals still contain water molecules. Together with the known locations of buried water ice, this provides a possible location for in-situ resource utilization to extract water, which is key to establishing a human base on Mars. Clay and salt are also common building materials on Earth.

Oxia Planum Water Rich Minerals

Second, even before humans traveled to Mars, hydrous minerals provided an excellent location for science. As part of this mineral mapping exercise, the clay-rich Oxia Planum site was discovered. These ancient clays include iron- and magnesium-rich minerals such as smectite and vermiculite. Not only could they help unravel the climate of Earth’s past, but they’re the perfect location to study whether Mars ever had life. As a result, Oxia Planum was proposed and eventually selected as the landing site for ESA’s Rosalind Franklin rover.

“That’s what interests me, and I think this kind of mapping work will help open up these studies,” Lucy said.

The more we learn about the planet when dealing with Mars, the more fascinating it becomes.

Notes to Editors

Mars orbit catalogue of water variation signatures (Mokas) In publication by J. Carter et al. Icarus.

M3 Project: 3 – Global Abundance Distribution of Martian Hydrated Silicates L. Riu et al published in IcarusVolume 374, 2022.

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