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To explain asteroid composition, scientists invoke nuts

Brazil nut effect may be behind space rocks’ lumpy surfaces

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1:52pm, August 15, 2014
asteroid Itokawa

NUT CASE  Large boulders speckle the surface of the asteroid Itokawa, an example of the Brazil nut effect.

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Brazil nut effect
\BRUH-zil nuht ih-fekt\ n.

The phenomenon in which a mixture’s larger objects, such as Brazil nuts in a can of mixed nuts, rise to the top when the mix is shaken vertically. Some scientists think that smaller nuts slip into the spaces under the larger ones during each shake.

Now researchers are using the Brazil nut effect to explain mysteries in space. Scientists report August 8 in the Monthly Notices of the Royal Astronomical Society that the effect could account for why only big boulders dot the surfaces of asteroids. The researchers calculate that asteroid-quakes and impacts from smaller space rocks could jostle an asteroid enough to cause larger rocks to rise to the surface.

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