The OSIRIS-REx mission to asteroid Bennu launches in six days.
Bennu is the Goldilocks of asteroids β not too small, not too far away and made of just the right stuff.
Of the more than 500,000 asteroids in our solar system, only 7,000 come relatively close to the Earth. Most of those are small, rapidly spinning asteroids. They either would be too dangerous to make contact with or may have shaken off their layers of loose rock during eons of spinning.
Only 26 asteroids were close enough and large enough to visit. Five were thought to have carbon.
The presence of that element is the whole point of the mission. Researchers hope to collect bits of asteroid chock-full of organic compounds dating to the birth of our solar system.
Carl Hergenrother, a scientist on the OSIRIS-REx team, decided to give the asteroid a closer look in 2005.
Peering through a University of Arizona telescope in the Santa Catalina Mountains with the aid of several colored filters, Hergenrother saw that Bennu, then simply known as 1999 RQ36, was bluish-black β a color that indicated the asteroid was probably carbon-rich.
Hergenrother and mission leaders at the UA Lunar and Planetary Laboratory decided that Bennu was just the right asteroid for a visit.
