Eros: The Ups and Downs PIA03111
Eros11 While NEAR Shoemaker did not directly measure gravity on Eros' surface, the spacecraft gathered other data that allow scientists to infer this measurement.
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Image Credit: Johns Hopkins University / Applied Physics Laboratory, NASA.  

While NEAR Shoemaker did not directly measure gravity on Eros' surface, the spacecraft gathered other data that allow scientists to infer this measurement. Radio tracking was analyzed to determine the asteroid's gravitational "pull" on the orbiting spacecraft. The many images of the asteroid, plus range measurements from the laser altimeter, measured the body's shape. Comparisons of the shape with the gravitational pull felt by the spacecraft from different parts of its orbit showed that the density of the interior to be nearly uniform. The asteroid's shape, density and spin combine to create a bizarre pattern of what is "uphill" and "downhill." In this view, a map of "gravitational topography" has been painted onto a shape model. Red areas are "uphill" and blue areas are "downhill." A ball dropped onto one of the red spots would try to roll across the nearest green area to the nearest blue area.  
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