After five years, NASA's Mars 2020 rover mission has a landing site penciled in. From a list of 60 candidate sites, the space agency has chosen Jezero Crater as the touchdown point for the nuclear-powered unmanned explorer designed to seek out places where life might once have existed and collect soil and rock samples for return to Earth via a future mission.

Located in the Syrtis Major region on the western edge of Isidis Planitia at 18.855°N latitude and 77.519°E longitude, Jezero Crater is 49 km (30.4 mi) in diameter and contains a fan delta rich in clays dating back 3.6 billion years when the Red Planet had abundant water. According to NASA, its varied geology with at least five different types of rocks that include clays and carbonates could help scientists to not only answer the question about whether life ever existed on Mars, but also about the planet's evolution.

The problem is that though Jezero Crater is desirable from a scientific point of view, from an engineering point of view it's less than optimal. The area is marked by a river delta, many small craters, cliffs, as well as scattered rocks and boulders. None of these are very friendly to landing a spacecraft.

According to NASA, this presents many challenges to the teams tasked with bringing the Mars 2020 lander down safely, but advances since the Curiosity rover landed in 2012 allows the space agency to operate in landing zones that are half the size. The biggest advance has been the development of Terrain Relative Navigation (TRN) that will provide the "sky crane" carrying the lander the ability to steer itself to avoid landing hazards. However, this still requires further analysis that will continue into late 2019 to find the precise site for the landing.

"Nothing has been more difficult in robotic planetary exploration than landing on Mars," says Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate. "The Mars 2020 engineering team has done a tremendous amount of work to prepare us for this decision. The team will continue their work to truly understand the TRN system and the risks involved, and we will review the findings independently to reassure we have maximized our chances for success."

NASA says that there are still many decisions to be made before Mars 2020 launches in July 2020, but the selection of the landing site will help scientists to focus their plans for exploring Jezero Crater and for collecting samples.

Source: NASA

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