Asteroid Bennu is of high importance to NASA, with the space agency’s Osiris Rex spacecraft arriving at the space rock last year. NASA’s Osiris-Rex will collect samples from Bennu and return them to Earth by 2023.
However, the space agency is at Bennu for another reason – there are small fears that the asteroid could come crashing into Earth within a few centuries.
One planetary astronomer, Michael Busch of the SETI Institute, said there is a chance the asteroid could hit Earth in 2175 and 2200, but this depends on the Yarkovsky effect.
The Yarkovsky effect is when an asteroid or celestial body changes its orbit due to small push of heat, either from itself expelling gasses or other celestial bodies including the Sun.
If the change in Bennu’s orbit is strong enough, its trajectory could fall into a collision course with Earth.
Mr Busch said there is a one in 27,000 chance this could happen, but said Osiris-Rex will likely rule this out with high precision measurements.
He wrote on Q&A site Quora: “There are a few cases like the asteroid Bennu. Bennu is just under 500 m in diameter, and as of the most recent assessment, it has a series of potential Earth impacts between 2175 and 2200. Impact probability is assessed at 1:2700.
“High-precision measurements by O-REx will improve our knowledge of Bennu’s trajectory, and will most likely rule out the potential impacts.”
But NASA has said that while there is a small chance Earth could be impacted, “over millions of years, of all of the planets, Bennu is most likely to hit Venus.”
For now however, NASA is focussing on returning samples from Bennu, which OSIRIS-Rex arrived at in December 2018 following a gruelling journey of over a billion miles.
OSIRIS-Rex has now completely mapped Bennu, and has selected four potential sites which it could select samples from.
The plan next is to whittle these sites down to two, where it will collect samples from a one-inch area.
NASA was not prepared for just how rocky Bennu would be, so it is looking for an area where samples are fine enough for the machine to ingest.
Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson, said: “We knew that Bennu would surprise us, so we came prepared for whatever we might find.
“As with any mission of exploration, dealing with the unknown requires flexibility, resources and ingenuity.
“The OSIRIS-REx team has demonstrated these essential traits for overcoming the unexpected throughout the Bennu encounter.”