Nasa to launch asteroid sample return mission

Nasa’s asteroid explorer OSIRIS-Rex is set to embark on a seven-year, round-trip mission tonight that will attempt to retrieve a sample of asteroid soil and deliver it back to Earth.

The countdown for Nasa’s OSIRIS-Rex mission has already started. The 3m cube fitted with a telescopic arm and a small heat-proof return capsule is sitting atop an Atlas 5 rocket at Nasa’s Cape Caneveral Air Force Station in Florida.

An hour after midnight GMT tonight, the rocket will shoot off towards the sky and send OSIRIS-Rex towards a 500m space rock called Bennu. Identified in 1999, according to astronomers Bennu is a potential hazard for life on Earth as it has a one to 2,700 chance of hitting the planet in the next two hundred years.

Before that happens, American scientists hope to learn every detail about the asteroid, thanks to the upcoming mission.

"We're going to asteroid Bennu because it's a time capsule from the earliest stages of solar system formation, back when our planetary system was spread across as dust grains in a swirling cloud around our growing protostar," said Dante Lauretta, lead researcher for the mission who works at the University of Arizona.

It will take OSIRIS-Rex 23 months to reach Bennu. Once it reaches its orbit in August 2018, the craft will spend almost two years studying, mapping and observing the space rock in preparations for the sample collection. The big moment will arrive in July 2020. OSIRIS-Rex will slowly lower itself towards Bennu’s surface, descending at speeds no greater than a quarter of a mile per hour.

Once within reach, it will deploy its telescoping arm, briefly touch the surface and suck in a sample of the surface dust. The researchers hope the craft will acquire at least 60 grams of asteroid material.

OSIRIS-Rex will immediately retreat back to orbit and store the sample in the protected capsule for safe return to Earth.

OSIRIS-Rex will only depart Bennu in March the following year. Its return to Earth is scheduled for September 2023. Once the solar-powered spacecraft reaches the Earth’s orbit, it will hopefully safely catapult the sample capsule, as this is expected to be the only part of the spacecraft that returns to the Earth’s surface. Protected by a sturdy heat shield, the capsule is designed to survive the fiery descent through the Earth’s atmosphere, landing with parachutes in the Utah desert.

The researchers hope data from the mission will help them not only better understand the geology of asteroids, but also better assess Bennu’s trajectory and evaluate the risk of it colliding with the Earth in future.

Nasa also hopes OSIRIS-Rex will demonstrate the advanced imaging and mapping techniques needed for future science missions and for upcoming commercial asteroid-mining expeditions.

Japan’s space agency JAXA previously managed to retrieve an asteroid sample and deliver it to Earth. Its Hayabusa 1 spacecraft brought a few grains of material from asteroid Itokawa to Earth in 2010. Japan’s second asteroid sample return mission is underway. Hayabusa 2, launched in 2014, is currently on its way to asteroid 162173 Ryugu. It is expected to come back to Earth in December 2020.

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