An artist's rendering of the space probe OSIRIS-REx.
One of the key goals of the OSIRIS-REx mission is to study the impact of the sun's heat on the orbits of asteroids with the potential to hit Earth and cause substantial damage.
The primary mission of OSIRIS-REx is to gather sample materials from the carbon-rich surface of Bennu and send it back to Earth for scientific analysis.
Asteroids like Bennu are such intriguing targets because they are the leftovers from the solar system's birth. So, once it has picked the likeliest spot and safest place to find some of these materials, the spacecraft will extend the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) - a 3.35-meter (11 ft) robotic arm - and grab a handful of matter from the surface.
"OSIRIS-REx seeks answers to the questions that are central to the human experience: Where did we come from?"
OSIRIS-REx will continue doing this over the next four weeks, during close flybys over Bennu's north pole, equator and south pole that will bring the probe as close as 4.4 miles (7.1 kilometers) to the asteroid's surface. This latest rock is named Ryugu and about double the size of Bennu. It was "flexed" in space for the first time on November 14.
Bennu is 76m miles (122m km) away so it took seven minutes for word of the success to reach flight controllers at Lockheed Martin in Littleton, Colorado, where the spacecraft was built.
In 2021, it will be time for the spacecraft to essentially turn around and begin its two-year journey home.
The sampler head is stored in the Sample-Return Capsule (SRC) and OSIRIS-REx will return to Earth.
For two years after the return, the sample will be cataloged and analyzed. OSIRIS-REx is the third mission in NASA's New Frontiers Program, which is managed by NASA's Marshall Space Flight Center in Huntsville, Alabama for the agency's Science Mission Directorate in Washington. The asteroid fits a number of criteria that make it intriguing and convenient.
Bennu is a carbonaceous primitive B-type asteroid with a cumulative 1-in-2,700 chance of impacting Earth between the years 2175 and 2199, according to NASA's 2016 Earth Impact Risk Summary.
Bennu is so small (about 0.05 percent of the mass of Mount Everest) that its gravity is almost negligible.
The data collected by OSIRIS-REx will prove useful in a variety of other ways as well, mission team members have said.
And OSIRIS-REx's precise tracking of Bennu through space will help researchers better understand the non-gravitational forces (specifically, the Yarkovsky effect) that shape asteroids' trajectories.
Another reason Bennu is chosen among over 500,000 known asteroids in the Solar System is its carbon-rich composition. Those like Bennu contain natural resources, such as water, organics and metals. It's because of objects like Bennu that these resources were delivered to Earth during its formation.
"But while the spacecraft might tell us some things about where we have been and where we are headed, it also can remind us of where we are right now", NASA officials said in a statement.