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Latest issue“science magazinePublished the first paper of the “Perseverance” exploration results, introducing the discovery of the Mars rover in the Jezero Crater-an ancient delta-lake system and flood deposits.
Traces of ancient aquatic life are usually preserved in the sediments at the bottom of the lake.
One of the main tasks of the Perseverance is to collect samples from the sediments at the edge of the Jezero Crater, and to be transported back to Earth for the research team to investigate, to identify whether life has ever existed on Mars and whether it has left a “biological imprint.”
BBC Science and Technology Correspondent Jonathan Amos said that the analysis confirmed that the location of the rover was once at the bottom of a large lake. There is a lake on the west side of the lake, where a meandering river flows into the lake; that should be It was 3.7 billion-3.5 billion years ago, when the climate of this red planet was much milder.
By analyzing the picture data returned from Mars, scientists determined that when this dry, barren, and wind-eroded basin was still a lake, the mouth of the river formed an impact delta.
The scene pictures also show that the rivers of the crater lake system have experienced severe floods. It may be at the end of the lake’s history. The power is so powerful that it can carry huge boulders and mud from dozens of miles upstream and rush into the lake. The boulder sank to the bottom of the lake and remained there until it was discovered by humans.
Previously, scientists inferred from the pictures taken from the orbit of Mars that the landform on the west side of the Jezero Crater is similar to the river delta on the earth, and Perseverance took pictures of exposed rocks there for the first time, confirming the tracking clues.
Based on the analysis of the flood sediments, scientists infer that the lake was in a calm state most of the time, until the climate changed drastically, triggering huge floods. Researchers hope to find more clues that can reveal the evolution of the climate there.
On February 18, 2021, the Perseverance landed at the bottom of Jezero Crater. NASA engineers from the Earth Control Center operated remotely to inspect and debug many instruments on the Mars rover. During this period, the rover remained stationary, but the two cameras on the rover did not stop working and continued to photograph the surrounding landscape.
These pictures and videos are transmitted to the earth. After processing and combining, the different sedimentary layers along the Kodiak strata are examined with extremely high resolution, the thickness of each layer, the lateral extent of the slope and the river are measured, and then the pictures are compared with the sedimentary layer pictures of other sections along the pit. , And finally came to a conclusion.
They believe that the sediments at this site were formed by water deposition, and they determined that it was once a delta at the intersection of rivers and lakes, rather than a sedimentary layer formed by wind or flaky flooding and its geological processes.
Another surprising discovery is the large rocks and pebbles embedded in the top layer of the delta sediments. The largest of them is one meter wide and estimated to weigh several tons. The research team believes that these rocks were brought into the crater by some force, probably at the edge of the crater or from 40 miles or more upstream from the river entrance.
According to the analysis of the current location and size of the rocks, the speed of the water rushing these big rocks into the lake is as high as 9 meters per second. They are embedded on the top of the older, finer-textured delta sedimentary layer, indicating that they took longer to settle. Night.
In other words, the fine sand and gravel in a river that merged into the lake was continuously deposited to form a delta. Later, a flash flood from the upper reaches of the river washed the boulder into the mouth of the lake and deposited in the delta. After billions of years of wind erosion, it formed today. Look.
Scientists hope that these sediments can help mankind uncover what happened to Mars a long time ago, how the climate has changed, and how the seas and rocks have changed.
Professor Sanjeev Gupta from Imperial College London is one of the main authors of the paper in the journal Science.
He told BBC News that analysis showed that “some changes have taken place in hydrology, but whether it is related to the climate, we don’t know.”
He explained, “You need something like a flood (huge energy) to move these boulders. Maybe there are glacial lakes upstream, and the flood leaks into Jezero.” He told BBC reporter Amos, on earth, in the Himalayas and other places. You can see the lake burst, and you can see these big rocks mixed with normal river sand in the Ganges Basin, which is the place where the glacial lake suddenly flooded.
The scientific team “Perseverance” will send the rover to the bottom of the main delta formation and drill where it is estimated to be fine-grained mudstone.
They will also explore a circle of carbonate rocks around the edge of the Jezero Crater, which may be the deepest shore of the crater lake.
If studying the sedimentary stratigraphy of the estuary delta of the Jezero Crater is of any significance, it should first be hoped to reveal the changes in climate, rivers, and environment during the period before the lake dried up.
The clue I was looking for now points out where the exploration should be focused first, and from which level of the sediment to start the study. After the Perseverance landed on Mars, it cruised for eight months and found clues to search for signs of life. The next step of exploration will no longer be aimless, but will concentrate on digging deep in certain locations.