Over two-years after launch, the NASA probe OSIRIS-REx will land on a skyscraper-sized asteroid on Monday for the first US mission to carry asteroid samples back to Earth. 

The over 800-million-dollar undertaking will provide pristine asteroid samples necessary for studying the early solar system, NASA says, and it will allow scientists to better understand the flight paths of potentially hazardous asteroids.

OSIRIS-REx is scheduled to land on the Bennu asteroid around noon EST (1700 GMT). The landing will be live-streamed on the NASA website.

The spacecraft was launched from Florida in September 2016 and has since hurled through space at speeds of over 100,000 kilometres per hour.

Once landing on Bennu the 3.5-meter-long probe will spend two years scudding around the surface. OSIRIS-REx has the capacity to return 46 kilograms of asteroid samples - the largest sample returned from space since the Apollo missions in the 1960s and early 1970s.

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.

Bennu - named after a mythological Egyptian deity by a third-grade contest winner - is one of the most hazardous asteroids known to NASA because of its large size and orbit. The chances of Bennu striking Earth are still a fraction of a per cent.