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The ejection events involve bits of space rock ranging from a few centimeters to up to tens of centimeters in diameter, Lauretta said. And the particles' velocities vary widely, too. Some move at up to 7 mph (11 km/h), fast enough to escape Bennu's weak gravity and cruise into interplanetary space. And other pieces merely mosey out, becoming trapped in orbit around Bennu for a spell and then falling back down onto the asteroid's surface.
"Basically, it looks like Bennu has a continuous population of particles raining down on it from discrete ejection events across its surface," Lauretta said. "This is incredibly exciting."
The team doesn't know what's spurring the ejection events. The ejections have been observed around the time of Bennu's closest passage to the sun during the asteroid's elliptical orbit, which occurred this year on Jan. 10. So, solar heating of the asteroid's surface and near-subsurface may be the main driver. But that's just speculation at the moment, Lauretta stressed.
www.space.com...
originally posted by: gortex
Not Earth shattering but quite interesting I think.
Could Bennu be a spent comet nucleus that still shows a bit of outgassing?
originally posted by: Phage
a reply to: wildespace
Any indication of scale?
(I'm lazy. Been trimming hedge all day.)
Though we aren't sure if outgassing is involved with Bennu or not, it wouldn't have to be the remnants of a comet to have outgassing. Asteroids can also have frozen material, and the distinction between comets and asteroids can be blurry.
originally posted by: wildespace
Could Bennu be a spent comet nucleus that still shows a bit of outgassing?
In the past, the Solar System seemed to be a tidy and well-organised place, with many families of objects neatly grouped together in different and distinct categories. There were planets and moons, comets and asteroids. But the nature of scientific discovery is the constant replacement of old knowledge with new, that most of the time leads to a major re-thinking and change of our established view of the Cosmos...
Further blurring the dividing line between asteroids and comets, a team of astronomers led by Michael Küppers, working at the European Space Agency’s Space Astronomy Centre near Madrid, Spain, just published its study on the results of its observations of Ceres with ESA’s Herschel Space Observatory...
What intrigues astronomers is the fact that this sublimation process of localised water ice on Ceres is common to comets as well. When comets lie far from the Sun beyond the Solar System’s frost line, they are nothing more than solid, dry objects, not unlike asteroids in appearance. When their orbits bring them adequately close to the Sun, solar radiation causes the ices that are hidden underground to heat up and begin to outgas, creating the spectacular views of bright comas and long, stretched tails of sublimation gas that comets are best known for. “The lines are becoming more and more blurred between comets and asteroids,” said Seungwon Lee of NASA’s Jet Propulsion Laboratory, who aided the team on their computer simulation studies.
originally posted by: firerescue
a reply to: wildespace
Could Bennu be a spent comet nucleus that still shows a bit of outgassing?
Some asteroids are described as "rubble piles" or "gravel banks"
Loosely conglomerate group of rock/ice held together by gravity
originally posted by: Phage
a reply to: wildespace
Black comets,
A husk of their former glory.
Gliding forever around the sun.