NASA’s OSIRIS-REx spacecraft has discovered ingredients for water on a relatively nearby skyscraper-sized asteroid, a rocky acorn-shaped object that may hold clues to the origins of life on Earth, scientists .
OSIRIS-REx, which flew last week within a scant 12 miles (19 km) of the asteroid Bennu some 1.4 million miles (2.25 million km) from Earth, found traces of hydrogen and oxygen molecules – part of the recipe for water and thus the potential for life – embedded in the asteroid’s rocky surface.
During its three year orbit of Bennu, 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.
Bennu was selected for a the OSIRIS-REx mission from over 500,000 known asteroids, due to it fitting a number of key criteria. These include:
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.
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.
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 of interest as it 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.