Nasa’s Osiris-Rex

Overview: 

NASA’s Osiris-Rex mission is all set to reach the Bennu asteroid – a rock that may predate the solar system – where its primary mission is to hover just above it, grab a sample of rock and dust and bring it back to Earth. 

Background:

The launch of the NASA OSIRIS-REx mission took place on September 8, 2016. Since then, the spacecraft has been two years travelling through space to reach its target, primitive asteroid Bennu, in October, 2018. 

About the mission:

• OSIRIS-Rex stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer.
• OSIRIS-REx is the third mission in NASA’s New Frontiers program, which previously sent the New Horizons spacecraft zooming by Pluto and the Juno spacecraft into orbit around Jupiter. 

Scientific Mission Goals:

• OSIRIS-REx will be conducting a range of scientific experiments in order to better understand the asteroid.
• The aim of the mission is to collect a sample of regolith- the loose, soil-like material which covers the surface of the asteroid.
• In July 2020, the probe will move to within a few metres of Bennu, extending its robotic arm to touch the asteroid’s surface. The arm will make contact with the surface for just 5 seconds, during which a blast of nitrogen gas will be used to stir up the regolith, allowing it to be sucked into the sample collector.
• OSIRIS-REx has enough nitrogen on board for 3 sample collection attempts, and NASA are hoping to collect between 60 and 2000g of regolith material to bring back to Earth. 

Why was Bennu chosen?

Proximity to Earth: In order for OSIRIS-REx to reach its destination in a reasonable timeframe, NASA needed to find an asteroid which had a similar orbit to Earth. Around 7000 asteroids are ‘Near-Earth Objects’ (NEOs). Out of these, just under 200 have orbits similar to Earth, with Bennu being one of these.

Size: Small asteroids, those less than 200m in diameter, typically spin much faster than larger asteroids, meaning the regolith material can be ejected into space. Bennu is around 500m in diameter, so rotates slowly enough to ensure that the regolith stays on its surface.

Composition: Bennu is a primitive asteroid, meaning it hasn’t significantly changed since the beginning of the Solar System (over 4 billion years ago). It is also very carbon-rich, meaning it may contain organic molecules, which could have been precursors to life on Earth.

Additionally, Bennu is a Potentially Hazardous Asteroid (PHA). Every 6 years, Bennu’s orbit brings it within 200,000 miles of the Earth, which means it has a high probability of impacting Earth in the late 22nd Century. 

Sources: TOI.