Asteroids are big chunks of leftover material from the days when the solar system was being formed.
However, they are not the solid, gigantic boulders portrayed in popular media, such as in movies and documentaries. Some of them are similar to piles of rubble held together by a small amount of gravity.
Should something hit these kinds of asteroids, it will leave a crater and eject some parts of the rubble into space, which is sort of what happened in a similar asteroid.
Researchers studying an asteroid called Bennu recently traced the progress of a landslide on the asteroid caused by an impact with another object through images collected by a NASA spacecraft, per Space.com.
The asteroid is classified as a "potentially hazardous asteroid" due to its size and its potential path bringing it close to Earth, per National Geographic.
Bennu Landslide Details
Researchers from the John Hopkins University Applied Physics Laboratory (APL) recently gained better insight into how rubble-pile asteroids such as Bennu take a hit thanks to images collected by NASA's OSIRIS-REx spacecraft.
The OSIRIS-REx spacecraft, or Origins, Spectral Interpretation, Resouce Identification, Security-Regolith Explorer, is a spacecraft designed to give experts more information about how the early solar system formed and how life began, per NASA. It was also used to help them better understand asteroids that could impact Earth in the future, such as Bennu.
A study titled "Orbit and Bulk Density of the OSIRIS-REx Target Asteroid (101955) Bennu" revealed that Bennu has roughly a 0.037% chance of colliding with Earth between 2175 and 2199.
The landslide detected by OSIRIS-REx was found to have progressed, with the rubble from the landslide settling somewhere in Bennu's equator. According to Mark Perry, a researcher at the John Hopkins University APL, this result is only possible if Bennu has certain properties at its surface, such as dry dust particles with little to no cohesion.
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The ejected material from the impact, called ejecta, from the five to 20 kilometer per second impact was expected to flash up and detach from the asteroid at an equally high velocity. However, if the object is loosely packed, as in the case of Bennu, the ejecta goes up at a lower velocity.
Aditionally, the impact made by the object, which was thought to be only about 20 inches, left a crater 230 feet wide.
Perry stated that the landslide could happen with an asteroid as small as Bennu even with its low gravity if the dust that covered it provides almost no cohesion.
He then explained that since Bennu is so small its escape velocity is less than a few tenths of a mile per hour, meaning that any ejecta thrust up from the impact could leave Bennu if they were faster than that. However, the ejecta's slow speeds are only possible if Bennu's surface is "even weaker than ver loose, dry sand."
"This extremely low surface strength also means the material on a slope is easily disturbed, and that's what's led to the landside, Perry said.
Significance Of Bennu's Landslide
The progression and detection of Bennu's landslide are said to be "critical to [humanity's] undertanding of rubble-pile asteroids."
Additionally, the more we learn about their evolution, composition, and structure, the more insight we gain into the role they played in forming the solar system and future worlds beyond Earth, according to Perry.
