Planetary Science Institute researchers Vishnu Reddy and Driss Takir studied the surface composition of near-Earth asteroid 2004 BL86 during its close flyby of Earth early this morning.

Remotely operating the NASA Infrared Telescope Facility (NASA IRTF) on Mauna Kea, Hawai'i, Reddy and Takir studied infrared sunlight reflected off the asteroid to determine its composition. They were part of a team of astronomers from around the world studying this object.

"Our observations show that this asteroid has a spectrum similar to V-type asteroids," said Reddy.

"V-type asteroids are basalt, similar in composition to lava flows we see in Hawai'i. The principal source of V-type asteroids is thought to be ancient basin-forming impacts on the south pole of the large, main-belt asteroid (4) Vesta.

"These impacts gave rise to the Vesta asteroid family spanning the inner part of the main asteroid belt, and some of those fragments in turn were transported to Earth-crossing orbits."

Vesta was the first target of NASA Dawn mission.

Photometric and radar observations by other astronomers also showed that 2004 BL86 is a binary asteroid, a system where two asteroids orbit their common center of mass.

2004 BL86 is a 300-meter diameter asteroid that made a close flyby of the Earth on Monday morning at a distance of 745,000 miles. It is the closest flyby of a large asteroid for the next 200 years.