As NASA prepares a sample return mission on asteroid Bennu, concerns regarding the massive space rock hitting Earth are beginning to emerge. Several factors in space, as well as a spacecraft landing on the asteroid, could send it into a direct collision path with the planet.

NASA recently announced that its OSIRIS-REx mission will head to Bennu to collect samples from the asteroid. According to the space agency, this asteroid was selected because it is a near-Earth object, which means it orbits close to the planet.

NASA has already selected four possible sites where the OSIRIS-REx spacecraft can land on the 1,640-feet long asteroid. Although the asteroid has a generally rocky surface, the space agency has identified certain areas where a sample-collecting mission can be successfully carried out.

NASA will most likely select a site with a smooth surface, but the agency noted that it is still prepared to land a spacecraft on rugged ground if needed.

“Although OSIRIS-REx was designed to collect a sample from an asteroid with a beach-like area, the extraordinary in-flight performance to date demonstrates that we will be able to meet the challenge that the rugged surface of Bennu presents,” the mission’s project manager Rich Burns of NASA’s Goddard Space Flight Center said in a statement.

“That extraordinary performance encompasses not only the spacecraft and instruments, but also the team who continues to meet every challenge that Bennu throws at us,” he added.

As a near-Earth object, Bennu is one of the asteroids that NASA is closely monitoring due to its potential to cause a major impact event on the planet. According to the space agency, the asteroid’s chances of hitting Earth are one in 24,000. The agency predicted that this could happen within the next 120 years.

Bennu’s possible collision with Earth depends on the Yarkovsky effect, which states that an asteroid could be nudged due to heat from escaping gasses or a nearby cosmic body such as the Sun, Express reported.

But aside from forces in space, NASA’s sample return mission could also alter the path of Bennu. Removing chunks from the asteroid could change how it spins, which could then send it to a path straight to Earth. In addition, a spacecraft landing and taking off from the asteroid’s surface might push it into a collision path with the planet.