NASA rover has explored surface sediments, not lake deposits, for eight years: study

In 2012, NASA landed the Curiosity rover in Gale crater on Mars, as many scientists believed the crater was the site of an ancient lake on Mars over 3 billion years ago. Since then, the rover has been driving performing geological analyzes with its suite of instruments for more than 3,190 sols (Martian days, equivalent to 3,278 Earth days). After analyzing the data, researchers at the Department of Earth Sciences, HKU’s Faculty of Science, proposed that the sediment measured by the rover during most of the mission did not actually form in a lake.

The team of researchers suggested that the large mound of sedimentary rock explored and analyzed over the past eight years actually represents sand and silt deposited as air drops from the atmosphere and disturbed by the wind. The weathering minerals formed by the interaction between water and sand did not occur in a lake environment. The “wet” environment, they suggest, actually represents an alteration similar to the formation of soil under rain in an ancient atmosphere that was very different from the present.

The discovery was recently published in Scientists progress in an article edited by postgraduate research student Jiacheng LIU, his advisor, Associate Professor Dr Joe MICHALSKI, and co-author Professor Mei Fu ZHOU, all affiliated with the Department of Earth Sciences. The researchers used chemical measurements and X-ray diffraction (XRD) measurements, in addition to rock texture images, to reveal how rock composition trends relate to geological processes.

“Jiacheng has demonstrated very important chemical patterns in rocks, which cannot be explained in the context of a lake environment,” said Dr. Michalski. “The key point is that some elements are mobile, or easy to dissolve in water, and some elements are stationary, or in other words, they stay in rocks. Whether an element is mobile or stationary does not depend only on the type of element but also on the properties of the fluid. Was the fluid acidic, saline, oxidizing, etc. Jiacheng’s results show that immobile elements are correlated with each other and highly enriched at higher altitudes in the rock profile. you see in the soils. Additionally, it shows that iron is depleted as weathering increases, meaning the atmosphere at the time was shrinking on ancient Mars, and not oxidizing like it is on today’s rusty planet. “

Understanding how the Martian atmosphere and the surface environment as a whole evolved is important for the exploration of possible life on Mars, as well as for our understanding of how the Earth may have changed early in its history. . Obviously, the study of Mars is extremely difficult and the integration of creative and technologically advanced methodologies is necessary. Liu and his co-authors made some intriguing observations through the use of remote sensing techniques to understand the chemical composition ancient sediments that inform about their Their data challenge existing assumptions for both the deposition environment of these unique rock formations and the atmospheric conditions in which they formed, rather than formation in a watery lake environment. Indeed, this work will inspire new and exciting directions for future research, ”added Assistant Professor of the Department of Earth Sciences, Dr Ryan McKenzie.

China successfully landed its first lander, Zhurong, on Mars in May this year. Zhurong is currently roaming the plains of Utopia Planitia, exploring mineralogical and chemical clues of recent climate change. China is also planning a sample return mission that may take place at the end of this decade.