Bennu asteroid Nasa Osiris-Rex
The Osiris-Rex probe will survey the potentially lethal asteroid Bennu, before returning to Earth with samples (artists' impression) Nasa

Scientists from Nasa have announced plans to send a probe to study a huge asteroid which it is feared may one day collide with the Earth, causing a potentially planet-wide catastrophe. The giant space rock, 101955 Bennu, which was discovered in 1999, has a diameter of 1,600ft (500m) and orbits the Sun every six years at a speed of 63,000mph.

In 2135 it will pass between the Earth and the Moon, which could potentially alter its orbit so much that it could collide with our planet later that century. It is believed that the impact of a giant asteroid wiped out the dinosaurs, and many scientists believe the danger from one hitting the Earth again is one of the biggest dangers for mankind.

It has been calculated that if Bennu struck the Earth, it would release the same energy as three billion tonnes of high explosive, equivalent to 200 Hiroshima bombs. That would cause a global catastrophe and a threat to mankind's survival, so Nasa is sending a probe to determine what exactly Bennu is made of to help ensure it isn't diverted into our path.

Nasa's Origins, Spectral Interpretation, Resource Identification, Security and Regolith Explorer probe – Osiris-Rex for short – will rendezvous with Bennu in October 2018. After circling the asteroid for a year and identifying a suitable landing place, it will land on the surface, collect samples and then return to Earth, arriving home in 2023.

The sampling technology used may then be further developed to mine other asteroids for precious minerals.

Bennu is potentially deadly, but scientists are excited about it, because it is believed to be rich in materials made of carbon – such as graphite – and so is similar to the asteroids which bombarded the Earth billions of years ago, "seeding" the planet with the elements needed for primordial life.

"Bennu is a carbonaceous asteroid, an ancient relic from the early solar system that is filled with organic molecules," Dante Lauretta, Nasa's principal investigator in charge of Osiris-Rex, told the Sunday Times. "Asteroids like Bennu may have seeded the early Earth with this material, contributing to the primordial soup from which life emerged."

Osiris-Rex will also be studying the effect of a newly discovered phenomenon, the Yarkovsky effect, on asteroids as large as Bennu.

"The Yarkovsky effect is the force that acts on an asteroid when it absorbs sunlight and then radiates it back into space as heat. It acts like a small thruster, constantly changing its course," said Lauretta. "Bennu's position has shifted 160km (100 miles) since 1999."