Context:

• NASA’s OSIRIS-REx spacecraft discovered evidence of water on a relatively nearby skyscraper-sized asteroid, Bennu, a rocky acorn-shaped object that may hold clues to the origins of life on Earth, scientists said on Monday.

Details:

• 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.
• Data obtained from the spacecraft’s two spectrometers, the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the OSIRIS-REx Thermal Emission Spectrometer (OTES) revealed the presence of molecules that contain oxygen and hydrogen atoms bonded together, known as ‘hydroxyls.’
• While Bennu itself is too small to have ever hosted liquid water, the finding indicates that liquid water was present at some time on Bennu’s parent body, a much larger asteroid.
• Asteroids are among the leftover debris from the solar system’s formation some 4.5 billion years ago.
• Scientists believe asteroids and comets crashing into early Earth may have delivered organic compounds and water that seeded the planet for life, and atomic-level analysis of samples from Bennu could provide key evidence to support that hypothesis.
• Scientists are still trying to understand the role that these carbon-rich asteroids played in delivering water to the early Earth and making it habitable.
• The probe, on a mission to return samples from the asteroid to Earth for study, was launched in 2016. Bennu, roughly a third of a mile wide (500 meters), orbits the sun at roughly the same distance as Earth.
• There is concern among scientists about the possibility of Bennu impacting Earth late in the 22^nd century. It is regarded as a Potentially Hazardous Asteroid, as its orbit brings it within 200,000 miles of the Earth, which means it has a high probability of impacting Earth in the late 22^nd Century.

About the Mission:

• OSIRIS-Rex stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer.
• It 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.
• It will spend two years travelling towards Bennu, arriving at the asteroid in August 2018. The probe will orbit the asteroid for 3 years, conducting several scientific experiments, before returning to Earth, with the sample capsule expected to land in Utah, USA in September 2023.

Scientific goals of mission:

• Scientific experiments to better understand the asteroid.
• To collect a sample of regolith- the loose, soil-like material, this covers the surface of the asteroid.
• The material returned is expected to enable scientists to learn more about the formation and evolution of the Solar System

Reason for Bennu being chosen for study:

• Proximity to earth and has a similar orbit to earth
• Being able to ensure that the regolith stays on its surface
• It is a primitive asteroid, not underwent much changes, which is of interest to study to understand better the beginning of the solar system