First discovered in September 1999, Asteroid Bennu swiftly earned almost unprecedented notoriety among space rocks. Space agencies including NASA are keeping a close eye on the rogue space rock for two reasons. It is hoped the ancient asteroid could inform scientists about the formation of life on Earth. And more intriguing still, Bennu has an estimated 1-in-2,700 chance of impacting out planet between 2175 and 2199 – making it the second-most dangerous known space rock.
For these reasons, NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) will attempt to obtain and return a sample from the near-Earth asteroid.
We knew that Bennu would surprise us, so we came prepared for whatever we might find
OSIRIS-REx principal investigator Dante Lauretta
And NASA has just announced it has selected there final four site candidates for the ambitious asteroid sample return attempt.
Since arriving at the asteroid in December 2018, OSIRIS-REx has mapped the entirety of Bennu to identify the safest and most accessible spots for the spacecraft to collect a sample.
NASA had originally planned to choose the final two sites by this point in the mission.
OSIRIS-REx’s earliest images, however, revealed Asteroid Bennu has an particularly rocky terrain.
Since then, the asteroid’s boulder-filled topography has created a challenge for the team to identify safe areas containing sample-able material, which must be fine enough – less than 1 inch (2.5 cm) diameter – for the spacecraft’s sampling mechanism to ingest.
Dante Lauretta, the NASA OSIRIS-REx principal investigator, 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.”
The NASA OSIRIS-REx mission now will spend four more months analysing the four candidate sites in detail, with a particular focus on identifying regions of fine-grain, sample-able material via high-resolution imagery of each potential site.
The original mission plan envisioned a sample site with a radius of 82ft (25m).
But such boulder-free sites of this size do not exist on Bennu, so NASA has instead targeted sites ranging from 16 to 3ft (5 to 10m) wide sites.
The four candidate sample sites on Bennu are designated Nightingale, Kingfisher, Osprey, and Sandpiper – all birds native to Egypt.
The naming theme complements the mission’s two other naming conventions – Egyptian deities – the asteroid and spacecraft – and mythological birds – surface features on Bennu.
NASA said in a statement: “The last of these types – saxum – is a new feature classification that the International Astronomical Union introduced earlier this year for small, rocky asteroids like Ryugu and Bennu.
“These surface features on Bennu will be named after mythological birds and bird-like creatures, complementing the mission’s existing naming theme, which is rooted in Egyptian mythology.”
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