Shulou(Shulou.com)11/24 Report--

CTOnews.com, May 18 (Xinhua) the current Mars is cold and dry and lacks traces of running water and life, but the Martian environment billions of years ago may have been very different.

Previous studies have proved that there was a large amount of liquid water on early Mars, and the paleo-ocean hypothesis was put forward through geomorphological analysis and numerical simulation. It is believed that a special marine sedimentary geological unit was formed in the paleo-ocean region, which is called the Northern Desert formation (VBF), but it lacks the support of in-situ exploration data. Therefore, this issue has always been the focus of controversy in academic circles.

An international research team led by Professor Xiao long, School of Geosciences, China University of Geosciences (Wuhan), comprehensively analyzed the scientific data obtained by the multi-spectral camera (MSCam) on the Mars rover, and found petrological evidence of marine sedimentary rocks on the surface of Mars for the first time, proving that the ocean once existed in the northern part of Mars.

The relevant research results are published in the comprehensive authoritative journal National Science Review (CTOnews.com with DOI:10.1093/nsr/nwad137) under the title of "evidence of Marine Sedimentary Rocks in the Utopian Plain: observation of the Zhu Rong rover".

In 2021, the "Zhu Rong" rover carried by China's Tianming-1 Mars mission successfully landed on the southern edge of the utopian plain in the eastern part of the northern plain of Mars, located in the northern wasteland formation near the ancient coastline proposed by our predecessors. it provides an opportunity to verify the existence of paleo-marine deposits.

Since landing, the Zhu Rong has been sailing south to the potential coastline and observing the strata of the northern wasteland formation along the way. " The Zurong traveled about 1921 meters (figure 1) and used different imaging and analysis systems to make detailed in-situ observations of outcrops and surface rocks. The navigation and terrain camera (MSCam) have obtained 106sets of panoramic images, detailing the surface morphology and structural features of many rocks near the route of the Zurong.

Fig. 1 "Zhu Rong" driving map and topography of the inspection area. "We looked at the photos sent back by the camera on the rover and found that the bedding structures of these exposed rocks are obviously different from the common volcanic rocks on the surface of Mars and the bedding structures formed by wind-blown sand deposits. The two-way flow characteristics indicated by these bedding knowledge are consistent with the low-energy tidal currents in the Earth's coastal-shallow sea environment," Xiao said.

Based on the rock images obtained by MSCam, Professor Xiao long's team analyzed in detail the surface structure of the rocks in the inspection area of the Zurong rover. Since the observed rocks are all located in the Zurong inspection area, the research team named the geological unit they represent: the Zurong section. In the study, the research team found that the rocks in the segment usually retain local lenticular staggered bedding fabric, mainly a variety of small staggered bedding, accompanied by a small amount of lenticular flattened bedding and small channel structures (figure 2). Among them, the strata that make up the staggered bedding overlap and tilt in two opposite directions, indicating the two-way paleocurrent environment.

In addition, the thickness and grain size of the strata are quite different in different directions, indicating that there is a strength difference between the paleocurrent in the two directions. This two-way flow model is usually formed by the action of fluids with periodic changes in flow direction, which is not common in eolian and fluvial environments, but is very common in the coastal-shallow sea environment of the earth. Compared with Earth, Mars has only two small moons, giving its surface a low-energy tidal system, which can only form small-scale bedding structures in this tidal environment. In addition, the bottom shape and sedimentary structures identified in the study have evidence to support that they are water deposits rather than eolian deposits.

Fig. 2 sketches of rocks and sedimentary beddings observed by the Zhurong, rock no. Sol50-08. The observation of the rocks in the Zhurong section in this study is the first direct in-situ exploration evidence to support the existence of the paleo-ocean in the northern plains of Mars. the location of the landing site of the Zhu Rong indicates that the observed sedimentary structure may have been formed during the retrogression of the paleo-ocean in the northern plain (figure 3).

Fig. 3 A map of ocean evolution patterns in the West. These sedimentary structures discovered in the northern wilderness formation in this study provide new implications for reshaping the history of Mars. "in the future, the in-depth exploration and sampling return of this area will deepen our understanding of the livability of Mars and the preservation of traces of life," Xiao said.

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