NASA’s OSIRIS-REx New Side Job: Hunt for Rare ‘Trojan’ Asteroids

NASA's OSIRIS-REx spacecraft will get another job done while heading towards its target asteroid Bennu -- to search for Trojan asteroids near Earth.

The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security- Regolith Explorer) spacecraft, the first mission to return asteroid samples to Earth, will take advantage of its two-year cruise to asteroid Bennu to scan Earth's path in search for rare and elusive Trojan asteroids, NASA said.

Trojans are asteroids that are constant companions to planets in our solar system as they orbit the sun, which are positioned at a near stable point 60 degrees in front of or behind the planet. They constantly lead or follow in the same orbit, which keeps them from colliding with their companion planets.

OSIRIS-REx will employ its MapCam imager to methodically scan the space, where Earth Trojans are expected to lie. According to NASA, many of these observations will closely resemble MapCam's planned activities during its upcoming search for satellites of asteroid Bennu, which makes the Earth-Trojan search an early rehearsal for the mission's primary science operations.

"The Earth-Trojan asteroid search provides a substantial advantage to the OSIRIS-REx mission," Dante Lauretta, OSIRIS-REx principal investigator and professor of planetary science at the Lunar and Planetary Laboratory at the University of Arizona, said in a statement.

"Not only do we have the opportunity to discover new members of an asteroid class, but more importantly, we are practicing critical mission operations in advance of our arrival at Bennu, which ultimately reduces mission risk."

Six planets in the solar system are known to have Trojan asteroids: Earth, Jupiter, Neptune, Mars, Venus and Uranus. Earth Trojans are extremely elusive; scientists have only discovered one - the 2010 TK7, which was discovered by NASA's NEOWISE project in 2010.

According to scientists, there should be more Trojans orbiting Earth, but they are difficult to detect because they appear close to the sun from Earth's point of view. In mid-February 2017, the OSIRIS-REx spacecraft will be positioned in an ideal spot where it could undertake a survey of the stable point in front of the Earth.

OSIRIS-REx is currently on a seven-year journey to rendezvous with near-Earth asteroid Bennu and bring back a sample to Earth. The sample could help provide scientists information about the formation of the solar system over 4.5 million years ago.