Space rendezvous with asteroid

NASA EXPLORER OSIRIS-REX TO CONDUCT SURVEY OF BENNU

Nasa’s deep space explorer Osiris-Rex flew on Monday to within 19km of its destination, a skyscraper-sized asteroid believed to hold organic compounds fundamental to life as well as the potential to collide with Earth in about 150 years.

Launched in September 2016, Osiris-Rex embarked on Nasa’s unprecedented seven-year mission to conduct a close-up survey of the asteroid Bennu, collect a sample from its surface and return that material to Earth for study.

Bennu, a rocky mass about 530m wide and shaped like a giant acorn, orbits the sun at about the same distance as Earth and is thought to be rich in carbon-based organic molecules dating back to the earliest days of the solar system. Water, another vital component to the evolution of life, may also be trapped in the asteroid’s minerals.

Scientists believe that asteroids and comets crashing into early Earth delivered organic compounds and water that seeded the planet for life. Atomic-level analysis of samples from Bennu could help prove that theory. But there is another, more existential reason to study Bennu.

Scientists estimate there is a one-in-2 700 chance of the asteroid slamming catastrophically into Earth 166 years from now. That probability ranks Bennu second on Nasa’s catalog of 72 objects near Earth potentially capable of hitting the planet.

Osiris-Rex will help scientists understand how heat radiated from the sun is gently steering Bennu on an increasingly menacing course through the solar system. That solar energy is believed to be nudging the asteroid ever closer toward Earth’s path each time the asteroid makes its closest approach to our planet every six years.

The mission’s spokesperson, Erin Morton, said: “By the time we collect the sample in 2020 we will have a much better idea of the probability that Bennu would impact Earth in the next 150 years.”

Scientists have estimated that in 2135, Bennu could pass closer to Earth than the moon, which orbits at a distance of about 402 000km, and possibly come closer still some time between 2175 and 2195.

Osiris-Rex reached the “preliminary survey” phase of its mission on Monday, soaring to within 19.3km of the asteroid.

The spacecraft will pass just 1.9km from Bennu later this month, when it will enter the object’s gravitational pull.–