NASA’s Perseverance Rover Completes 1,000 Days on Mars, Discovers Evidence of Ancient Martian Lake

On February 18, 2021, NASA's Perseverance Rover made its landing on Mars after spending 29 weeks of interplanetary travel. Its mission was to conduct surface-based studies of the Martian environment and look for signs of biosignatures in rock samples.

Mission Accomplished

After completing 1,000 days on Mars, Perseverance accomplished its mission of exploring an ancient river delta which holds the evidence of a lake that existed billions of years ago. The discoveries were shared at the American Geophysical Union fall meeting in San Francisco on December 12.

NASA chose Jezero Crater as a landing site because of clear evidence that it was once filled by a lake as shown in orbital imagery. Lakes are recognized as potentially habitable environments, while delta rocks serve as fossils in the geologic record when looking for signs of ancient life. According to Perseverance's project scientist Ken Farley from California Institute of Technology, they pieced together the geologic history of the crater after thorough exploration. This helped them describe its lake and river phase from beginning to end.

Almost 4 billion years ago, Jezero was created from an asteroid impact on the red planet. When Perseverance landed, it was revealed that its crater floor is made of igneous rock formed either from magma underground or from volcanic activity at the surface. NASA also found sandstone and mudstone which indicate the arrival of the first river in the crater hundreds of millions of years later. Meanwhile, the presence of salt-rich mudstone above the rocks signal the presence of a shallow lake that experienced evaporation. This led the team to believe that the lake grew as wide as 22 miles (35 kilometers) in diameter and as deep as 100 feet (30 meters).

During the later stage, the fast-flowing water might have carried in boulders from outside Jezero, spreading them atop of the delta and elsewhere in the crater. Although the experts were able to see a broad outline of the chapters in Jezero's history, getting up close with Perseverance was still required to really understand the timeline in detail.

Valuable Rock Samples

The rover also accomplished its mission to be the first to collect and cache Martian rock and regolith. These rock samples will be used in characterizing the geology and past climate of Mars. The gathered samples, as big as a piece of classroom chalk, are kept in special metal tubes as part of the Mars Sample Return campaign. By transporting the tubes back to Earth, scientists will be able to study the rocks without the need for powerful lab equipment that are too large to take to Mars.

To date, the six-wheeled rover has collected a total of 23 samples which reveal the geologic history of Jezero Crater. One of these samples is the Lefroy Bay which contains a large quantity of fine-grained silica, known here on Earth for preserving ancient fossils. Another rock sample is called Otis Peak which holds a crucial amount of phosphate, a compound often associated with life as we know it. Both of the samples are also rich in carbonate which can preserve a record of the environmental conditions of the geologic time when they were formed.

NASA team targets to collect the sample called the Bills Bay which was also spotted to contain carbonates. These rocks were also rich in silica, a compound which is excellent in preserving organic molecules such as those related to the formation of life.

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