At Bennu, NASA finds a mysterious, boulder-strewn asteroid

After touring greater than 2 million kilometers by means of outer area over the course of 27 months, NASA’s OSIRIS-REx spacecraft arrived on the asteroid Bennu in early December of final yr. Since coming, the spacecraft’s five scientific devices have been surveying the 490-meter huge asteroid to higher perceive its properties and discover a protected touchdown website from which to collect samples for a return to Earth. On Tuesday, the primary outcomes of those scientific inquiries have been revealed in seven papers that appeared in Nature and a handful of its analysis journals. The seven articles are collated on this web site.

In some respects, Bennu is about what scientists anticipated—a “rubble pile” of stony meteorites which have aggregated beneath the effect of microgravity. Scientists must remain in a position to decide that the density of the asteroid is about 1,190kg per cubic meter. Using comparability, a potato has a thickness of approximately 700kg per cubic meter, and dry gravel about 1,500kg per cubic meter.

With a median albedo of 4.4 p.c, this asteroid is without the doubt one of the darkest objects within the Photovoltaic System. What shocked scientists, nonetheless, is the general variety of the albedo, or reflectivity of Bennu’s floor. The albedo ranges from the extraordinarily darkish—like freshly poured asphalt, at three.three p.c—as much as almost 15 p.c. In one of many analysis papers, mission scientists expressed concern that the sudden variance of Bennu’s albedo might confound the spacecraft’s lidar steering system because it approaches the asteroid to collect a pattern.

Fortuitously, the mission planners left loads of time for merely such research because the sampling maneuver won’t happen till July 2020. Till then, OSIRIS-REx will examine the asteroid in more substantial element—mapping the topology of the area rock to a better decision than even the Earth’s floor. The map of Bennu can have on the order of 5cm spatial and some cm vertical decision. This could assist NASA to resolve a number of the scientific mysteries raised by preliminary observations and discover a protected sampling web site.

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