NASA probe successfully collects asteroid sample for Earth return

On Tuesday evening at 23:12 BST, NASA’s OSIRIS-REx probe made brief contact with the near-Earth asteroid Bennu to successfully collect a sample of rocks and dust for study upon its return to Earth. 

Launched in 2016, OSIRIS-REx reached Bennu in late 2018 and has spent the last couple years orbiting and surveying the 490m diameter asteroid. The probe identified suitable sampling sites that would cause the least difficulty for the probe, while also providing a sample rich with information for scientists to study. Four of these were identified and named, with sample site Nightingale being designated the primary site and the one that the probe made contact with this week. 

Using a 3.3-metre-long arm, the probe released a burst of pressured nitrogen gas to kick up and capture loose regolith at the sample site. Nitrogen was chosen as it is relatively inert and thus unlikely to react with and affect the sample. Currently, the exact details of the sample are yet to be communicated to the researchers, however they hope that around 60g of material was scooped up. If substantially less material was collected, the probe will be sent to backup site Osprey in a few months’ time in order to collect more material.  

It is hoped that the sample will reveal the story of the infant Solar System; many asteroids are remnants from the planet formation phase and could reveal a great amount of information about the formation of our own planet. They could also enlighten us about the origin of life; organic molecules such as amino acids, the building blocks of proteins, have been found in meteorite samples from Earth. However, meteorites that crash onto our planet are subject to extreme temperatures as well as additional reactions with gases in our atmosphere, so a sample taken directly from an asteroid may be able to shed more light on the answers we are looking for. 

This isn’t the first time that humanity has managed to scoop up an asteroid sample for return to Earth; Japan’s Aerospace Exploration Agency (JAXA) beat NASA to it by a year. Hayabusa2 launched in 2014 and last year it grabbed a sample of a different near-Earth asteroid, Ryugu. It is scheduled to arrive back on Earth at the end of this year, meaning there is not long left until scientists can study a pristine asteroid sample. 

OSIRIS-REx, meanwhile, is scheduled to depart Bennu’s orbit in March 2021 and will return with its sample in 2023. After Tuesday’s successful sampling, NASA Administrator Jim Bridenstine said “we are on the way to returning the largest sample brought home from space since Apollo. If all goes well, this sample will be studied by scientists for generations to come.” 

An additional objective of this mission is to study the Yarkovsky effect on Bennu. The Yarkovsky effect is the name given to the effect of thermal radiation on a body’s orbit. As photons carry momentum, when heat is radiated away from a body anisotropically, it can alter the trajectory of the body due to the imbalance of force imparted on the object. Scientists are particularly interested to study this effect on Bennu, an asteroid that has a very low chance of cataclysmically impacting Earth in around 150 years’ time. This means that the research could allow us to figure out the best methods for diverting any asteroids heading our way, thereby ensuring humanity’s continued survival. 

OSIRIS-REx is part of NASA’s New Frontiers programme, which includes Pluto probe New Horizons, Jupiter probe Juno, and Dragonfly, an upcoming project to explore Saturn’s moon Titan.