A two-hour launch window opens Thursday at 7:05 p.m. for the Origins Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx) mission aboard a United Launch Alliance (ULA) Atlas V-411 rocket.

Over the next two years, OSIRIS-REx will travel to the 1,650-foot-wide near-Earth asteroid 101955 Bennu. The spacecraft will then spend two years studying the asteroid and collecting a pristine surface sample for return to Earth in September 2023, the first U.S. mission to do so and the largest sample of an extraterrestrial body since the Apollo missions.

Discovered on Sept. 11, 1999, by the Lincoln Laboratory Near-Earth Asteroid Research Team at Socorro, New Mexico, Bennu is a time capsule from the earliest stages of solar system formation. The mission will bring back samples of the asteroid where researchers hope to find evidence of water ice and organic material, key compounds that may have led to habitability here on Earth.

Bennu offers an environment which was erased on Earth during the late heavy bombardment period, where millions of asteroids collided with Earth, essentially sterilizing it.

Bennu was selected from over 500,000 candidates because of its “size, primitive and carbon-rich composition and orbit make it one of the most fascinating and accessible asteroids” according to Christina Richey, OSIRIS-REx deputy program scientist at NASA Headquarters in Washington, D.C.

During that two-year study, Bennu’s orbit, particularly how the solar energy it absorbs and later rates away, like asphalt on a hot day, will be studied in detail. Bennu is currently number three on the Jet Propulsion Laboratory’s (JPL) Sentry Risk System Monitoring table for possible Earth collision. However, the latest calculations put that risk of Earth impact at 1 in 2,700 near the end of the 22nd century.

Previously known as Asteroid 1999 RQ36, Bennu was renamed in the 2013 Name an Asteroid contest sponsored by the Planetary Society.

Michael Puzio, a then third-grade student from Greensboro, suggested the name because the Touch-and-Go Sample Mechanism (TAGSAM) arm and solar panels on OSIRIS-REx reminded him of the neck and wings in drawings of Bennu, the ancient Egyptian deity usually depicted as a gray heron.

When Puzio learned he had won the contest, he said, "It's great! I'm the first kid I know that named part of the solar system!”

The name Bennu struck a chord with the selection team which included the mission’s principal investigator Dante Lauretta. Bennu is associated with creation and rebirth in Ancient Egyptian mythology, representing the first life to appear.

Something to watch for in Thursday’s launch is the rocket lifting OSIRIS-Rex. The United Launch Alliance (ULA) Atlas V 411 rocket is just the fourth launch of the Atlas V with just a single strap-on solid rocket motor. The configuration was previously used in a classified launch of satellites for the National Reconnaissance Office from Vandenburg Air Force Base, Calif. and a commercial satellite from Cape Canaveral. This asymmetric configuration is counteracted by pivoting of the nozzles of the liquid fueled RD-180 engine to keep the rocket on course during ascent.

Last week’s explosion of the SpaceX Falcon 9 during a static fire test occurred just over a mile south of the vertical integration building where the Atlas V rocket and OSIRIS-REx were being prepared for launch. The spacecraft and rocket were protected inside that building at the time of the explosion. NASA and ULA also completed a "crossover assessment" review last weekend verifying that no hardware or other resources shared between the two launch complexes were impacted by the accident.

The launch weather forecast from the 45th Weather Squadron at Cape Canaveral Air Force Station calls for 80 percent probability of favorable weather for launch on launch day, decreasing to 70 percent should there be a 24 or 48-hour delay. Live coverage of the launch begins on NASA-TV at 4:30 p.m., with a launch window open from 7:05 to 9:05 p.m.