Curiosity roamed the same giant crater for 9 years. It may not be what we thought

When exploring alien worlds, it’s important to know exactly what to look for – and to reanalyze the rock samples taken from them storm pit On Mars This suggests that these ancient grains may not be the lake sediments we thought they were.

According to a new study on the chemistry of crater sediments, rock deposits – captured by Curiosity of Over the past nine years or so, it’s likely the result of airborne particles in the crater, before being held in place by purely weather conditions.

The team behind the new research argues that the chemical elements in these samples – those that have survived billions of years – do not match what one would expect from an ancient lake environment.

Mount Sharp in Gale Crater. (NASA’s Curiosity Mars probe)

“The important point is that some elements are mobile, or easy to dissolve in water, and some elements are immobile, or in other words, they remain in the rocks”, Planetary geologist Joe Michalsky says: from the University of Hong Kong.

“Whether an element is mobile or not depends not only on the type of element but also on the properties of the fluid.”

Thanks to a combination of chemical measures, X-ray diffraction (XRD) and tissue analysis, the team found evidence of a type of erosion that contradicts the Great Lakes hypothesis, indicating that most of the sediments were deposited in drier conditions.

The researchers say that airborne dust and volcanic ash likely make up the majority of the sediment, with further weathering due to precipitation or snowmelt. Only a small part of the sediment exactly matches its composition under the lake.

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The new analysis points to immobile chemicals that are closely related to higher elevations, which in turn could be evidence that Gale Crater’s water cover was shallower and transient than previously thought.


above: How water filled up from Gale’s Hole is shown in the lake hypothesis (left) and the new hypothesis (right).

“This refers to weathering from top to bottom as you can see on Earth”, Michalsky this. “more, [the study] He explains that iron is depleted with increased weathering, which means that the atmosphere at that time was shrinking on ancient Mars and not oxidizing as on our rusty modern planet.

Gale Crater was chosen as Curiosity’s landing site when it fell from space in 2012 because it was believed to have been home to a lake billions of years ago. Since then, he’s spent more than 3,000 Martian (or Martian) days studying rocks.

In addition to changing the approach to sediment analysis, it could also change scientific thinking about how the Martian climate has changed over the ages — there may have been frequent, temporary wet periods rather than long ones, for example. It also has implications for whether or not life exists on this planet.

However, it is worth remembering how difficult it is to put together the origins of Gale Crater. We’re not just looking back billions of years, but millions of miles back – and there’s probably a lot more to come from Curiosity and the rocks it collects.

“This is one of the big limitations of attempts at remote sensing and science on other planets,” said planetary scientist Tanya Harrison of the imaging company Planet Labs, who was not involved in the study. inverse.

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We often get vague data that can indicate multiple ideas. “

The search was published in scientific progress.

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