Bennu is a potentially hazardous c-type (carbonaceous) asteroid discovered on September 11, 1999. Around 75% of known asteroids are c-types. It is listed on the Sentry Risk Table,  which monitors and analyzes celestial objects on a near-Earth trajectory, predicting any possible collisions. Upon detection of an object, the results are published by the Near Earth Object Program, which is humanity’s front line of defense against any objects that will suffer us the same fate as the dinosaurs, though they sure could certainly use some orbital defense batteries sometime in the next century.

Bennu ranks high on the list of potentially hazardous objects, number 2 behind 29075 (1950), with a 1 in 2700 chance of striking our planet between the years 2175 and 2199. So have no fear, the Bruce Willis of the future will have to deal with that one. Bennu’s next close fly by will occur in 2060, when Bennu will pass Earth about 384,472 kilometers away (238,900 miles), twice the distance between the Earth and Moon, though there remains a possibility its trajectory could change at any given moment, resulting in difficulty to predict Bennu’s future trajectory. Hence the orbital batteries.

 The asteroid which caused the Chicxulub crater, speculated to cause the Cretaceous-Paleogene extinction event, was about 11- 81 kilometers in length. To contrast, Bennu measures 492 meters in diameter, approximately 1600 feet or a third of a mile long, though several other details must be taken into account in the event of a potentially catastrophic asteroid impact.

This mosaic image of asteroid Bennu is composed of 12 PolyCam images collected on Dec. 2 by the OSIRIS-REx spacecraft from a range of 15 miles (24 km). Credit: NASA/Goddard/University of Arizona.

Credit: Lawrence Livermore National Laboratories.

The Arecibo Observatory in Arecibo, Puerto Rico.

The Arecibo Observatory, where James Bond dropped 006 in Goldeneye, and the Goldstone Deep Space Network actively monitor Bennu, along with OSIRIS REX, fresh on the scene to extract some samples and map the surface to learn even more about this particular rock, including its mass and what it likes to do for fun. Since arriving on Bennu, NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-Rex) discovered water trapped inside the clay that composes the asteroid, resulting in further speculation regarding the curious nature of Bennu and its place in our Solar System. Starting in February 2019, OSIRIS-Rex will map the asteroid, preparing the following phases of its mission to extract samples from Bennu’s surface.

OSIRIS Rex will return to Earth sometime in 2023, when researches will study the extracted samples. Expected research outcomes include a better understanding of how early celestial bodies were formed in the solar system, leading to perhaps even greater implications involving the formation of planets.


This artist’s concept shows the OSIRIS-REx spacecraft collecting a sample from Bennu. Credit: NASA