Global map of hydrated minerals on Mars

(ESA)

While Mars is a bleak desert today, lakes and rivers were very much present on its surface until three billion years ago. However, the disappearance of water didn’t happen overnight. In fact, the ancient water never completely disappeared — it remains trapped within the minerals in Mars’ crust and has predominantly shaped the planet’s geology.

Now, scientists from the European Space Agency (ESA) have mapped these aqueous mineral deposits to understand how the Martian geology changed with time, and whether the planet was ever capable of supporting life.

The map has been created using over a decade’s worth of data collected by ESA’s OMEGA (Mars Express Observatoire pour la Mineralogie, l’Eau, les Glaces et l’Activité) and NASA’s CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) instruments. While OMEGA provides global coverage of Mars at higher spectral resolution and with a better signal-to-noise ratio, CRISM provides high-resolution spectral imaging of the localised surface patches of Mars, such as rover landing sites.

Mapping and quantifying Martian minerals

Global map of hydrated minerals on Mars (ESA)

Global map of hydrated minerals on Mars

(ESA)

The mapping has exhibited a diversity of mineralogy in geological settings, similar to what it’s like on our home planet,

On Earth, when water interacts with rocks, different types of clay minerals are formed. Take the example of smectite and vermiculite formation — they are a byproduct of the interaction of small quantities of water with iron and magnesium from volcanic rocks. But when the amount of water is relatively high, the same rocks can be altered to leave behind aluminium-rich minerals like kaolinite.

While scientists knew of only 1000 such geological outcrops on Mars ten years ago, the new map has revealed hundreds of thousands of such areas in the oldest parts of the planet, thereby providing a better insight into the planet’s minerals.

“I think we have collectively oversimplified Mars,” said John Carter, a scientist from Institut d’Astrophysique Spatiale (IAS) and Laboratoire d’Astrophysique de Marseille (LAM), Université Paris-Saclay and Aix Marseille Université, France. “This work has now established that when you are studying ancient terrains in detail, not seeing these minerals is actually the oddity,” he elaborated.

But now, the big question is whether the presence of water on Mars was more persistent, or if it remained confined to shorter, more intense episodes.

Before the mapping, scientists also believed that when water persisted on Mars, only a few types of clay minerals were created, and as the water gradually dried up, salts were produced across the planet.

But according to this new map, there has been an intimate mixing of salts and clays in some cases; and some salts may, in fact, even be older than some clays.

“The evolution from lots of water to no water is not as clear cut as we thought. We see a huge diversity of geological contexts, so no one process or simple timeline can explain the evolution of the mineralogy of Mars. That’s the first result of our study,” John explained.

“The second is that if you exclude life processes on Earth, Mars exhibits a diversity of mineralogy in geological settings just as Earth does,” he added.

After the successful mapping, the researchers are now trying to quantify the amounts of the minerals as well.

“If we know where and in which percentage each mineral is present, it gives us a better idea of how those minerals could have been formed,” said Lucie Riu, another scientist involved in the study.

Both mapping and quantifying will also provide possible locations for extracting water, which could help us determine where humans could potentially land during future Mars missions.

Global map of hydrated minerals on Mars (ESA)

Global map of hydrated minerals on Mars

(ESA)

Furthermore, the mapping has also led to the discovery of the new clay-rich site, Oxia Planum. The site was full of iron and magnesium-rich minerals of smectite and vermiculite, which effectively provides newer insights into the red planet’s past climate.

“As ever when dealing with Mars, the more we learn about the planet, the more fascinating it becomes,” said Lucie.

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