NASA spacecraft observes particle plumes erupting from the surface of asteroid Bennu

Bennu is a potentially hazardous asteroid, first spotted in 1999

NASA's OSIRIS-REx spacecraft, which has been orbiting the near-Earth asteroid Bennu for the several weeks, has noticed particle plumes emanating from the surface of the asteroid - a finding that scientists say was completely unexpected.

Bennu is a potentially hazardous asteroid, first spotted in 1999. This carbon-rich asteroid is thought to have been created by the leftover materials from the formation of the solar system.

NASA's OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) mission was launched in 2016 to study the potentially hazardous asteroid, and to obtain at least 60 grams of regolith samples from the its surface for further analysis by scientists on Earth.

The sample, which will arrive back on Earth in 2023, is expected to help improve scientists' understanding about the formation and evolution of the Solar system and the sources of organic molecules on Earth.

OSIRIS-Rex arrived at Bennu in the first week of December, after completing a journey of about 2 billion kilometres, making this asteroid the smallest body ever orbited by spacecraft in our solar system (or beyond it).

For the past several weeks, it has been orbiting the asteroid and observing the surface in detail.

"The discovery of plumes is one of the biggest surprises of my scientific career," said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson.

Particle plumes on Bennu were first observed on 6th Jan. Subsequently, scientists increased the frequency of observations and discovered more particle plumes on Bennu's surface.

While most of the particles were ejected clear of the asteroid, there were some particles that circled Bennu for some time and eventually returned to its surface.

Another finding that has perplexed NASA scientists is the presence of large boulders on the asteroid.

Earlier telescopic observations from Earth had indicated that Bennu's surface could be having at least some relatively large, smooth spots ideal for regolith sample collection.

However, latest observations by OSIRIS-REx reveal that Bennu is actually much more rugged, featuring a surface strewn with all kinds of large rocks and bounders.

The new finding has forced the mission team to alter its plan for sample collection. NASA scientists are still trying to identify a site ideal for Touch-and-Go sample collection exercise on Bennu. Large number of boulders on the surface also means the spacecraft will need to perform accurately during its descent to the surface than originally planned.