Unless something goes catastrophically wrong, the seismic signals that InSight might hear will not emanate from the rover itself. Perseverance is to be lowered to the surface from a hovering crane, bumping to the ground gently at slower than 2 miles per hour. Rather, scientists will be sifting through InSight’s seismic data for signs of the impacts of two 170-pound blocks of tungsten metal that helped keep Perseverance in a stable, balanced spin during its 300-million-mile trip from Earth. At an altitude of 900 miles above Mars, they will be jettisoned as junk, and without parachutes or retrorockets to slow them down, they will then slam into the surface at some 9,000 m.p.h. “This enormous speed means that they’ll make quite a substantial crater,” Mr. Fernando said. In 2012, similar tungsten blocks from the Curiosity rover, which is almost the same design as Perseverance, left scars visible from orbit.
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