The Curiosity Rover MastCam camera captured an image of the layered sedimentary rocks that make up Mount Sharp. To understand how rocks change, the rover drove from Gale crater's floor up through these hills. From the beginning of the mission, the rover has traversed rocks at more than 400 meters elevation. Credit: NASA's Mars Curiosity RoverNASA launched Curiosity the Mars rover Curiosity into the Gale crater in 2012. This Gale crater was believed to have been the location of an ancient lake that existed on Mars over 3 billion years ago. The rover has been moving along since then, performing geological analyses using its suite of instruments for more than 3,190 sols (martian day equivalent to 3278 Earth days). Researchers from the Department of Earth Sciences at HKU have concluded that the sediments that were measured during the majority of the mission didn't actually form in a lake.Researchers suggested that the large amount of sedimentary rocks analyzed over the past eight years may actually be sand and silt, which were deposited in the atmosphere as air-fall and then reworked and moved by the wind. The interaction of water and sand didn't create the alteration minerals. They propose that the "wet" environment is weathering similar to soil formation in a rainy atmosphere.Jiacheng LIU (a research postgraduate student), his advisor Professor Joe MICHALSKI and co-author, Professor Mei Fu ZHOU all of whom are associated with the Department of Earth Sciences, published the discovery in Science Advances. To determine how rock compositional trends relate to geological processes, the researchers used chemistry and X-ray diffraction measurements (XRD).Dr. Michalski stated that Jiacheng had demonstrated very important chemical patterns within the rocks. These patterns cannot be explained in a lake environment. Dr. Michalski stated that while some elements can dissolve easily in water, others are more mobile or remain in the rock. It depends on the type of element and the fluid's properties whether an element is mobile/immobile. Did the fluid react with acidic, saline or oxidizing elements? Jiacheng's results showed that immobile elements are strongly enriched at higher elevations within the rock profile. This suggests that weathering occurs from the top, as seen in soils. He also shows that iron depletes as weathering increases. This means that ancient Mars' atmosphere was not oxidizing like modern-day, rusted planets.These images depict Gale crater from High Resolution Stereo Camera images (HRSC), with the elevation colored in blue. The left image shows the standard model in which Gale crater was assumed to have had a large lake. It is flooded to at most 4,000m. The model suggested by Liu and colleagues is shown on the right. It shows that only small shallow lakes existed on Gale crater's floor. The crater was flooded to an elevation of about 4,500m. The majority of the sediments were formed from the atmosphere, as air-fall deposits. They were later weathered by precipitation and ice-melt. The landing site of the rovers is marked by a star. Credit: ESA/HRSC/DLRIt is crucial to understand how the Martian atmosphere and its surrounding environment evolved. This will allow us to explore the possibility of life on Mars. It is not easy to study Mars. Therefore, it is important to combine creative and technologically advanced methods. Liu and his co-authors made fascinating observations using remote sensing techniques to determine the chemical composition of ancient sediments. This information is crucial for understanding their early development. These data challenge existing hypotheses about the formation of these rare rock formations as well as the atmospheric conditions under which they formed. In particular, the authors suggest that weathering occurred in a subareal environment analogous to a desert. This is in contrast to formation in an aqueous lake environment. This work will certainly inspire new and exciting directions in future research," Dr. Ryan McKenzie, Assistant Professor at Department of Earth Science, said.China successfully landed Zhurong, its first lander on Mars, in May of this year. Zhurong is currently exploring the plains at Utopia Planitia for chemical and mineral clues regarding recent climate change. China also plans a sample return mission, which is likely to take place at the end this decade.Continue reading NASA Mars Rover begins to collect rock for alien lifeJiacheng Liu et. al., Intense Subaerial Weathering of Eolian Sediments in Gale crater on Mars, Science Advances (2021). Information from Science Advances Jiacheng Liu et. al., Intense Subaerial Weathering of Eolian Sediments in Gale crater on Mars, (2021). DOI: 10.1126/sciadv.abh2687
