OSIRIS-REx image
Image of Earth and Moon captured by OSIRIS-REx during its mission to asteroid Bennu. NASA/OSIRIS-REx team and the University of Arizona

NASA's OSIRIS –REx (Origin, Spectral Interpretation, Resource Identification, and Security- Regolith Explorer) Spacecraft has sent back some of the most impressive photos of Earth and Moon from distant space during its expedition to asteroid Bennu, a member of Appolo group of asteroids which passes near the earth.

The photos were taken on October 2, 2017, when it was around 3 million miles (5 million kilometers) away from earth. This distance was around 13 times the distance between Earth and Moon.

OSIRIS-REx's MapCam instrument had taken the images in three colors, red, green and blue using three different color filters. NASA researchers later combined these images to get the multicolored images of the earth and the moon.

OSIRIS-REx had been launched from earth in September 2016 for the surface expedition of the asteroid Bennu and to return samples from it to Earth. It has been expected to reach Bennu in December 2018. The spacecraft is the first mission ever to land in an asteroid, which is currently very far from the earth.

Earth
Image was taken by NavCam 1 on September 22, 2017, as OSIRIS-REx completed an Earth gravity-assist maneuver—flying close enough to our planet to steal some momentum and speed up the craft on its way to Bennu. This is the view from 110,000 kilometers (69,000 miles) away. OSIRIS-REx - NavCam1

Bennu's carbon-rich rock composition gives hopes of possibilities of life and organic molecules in it. The asteroid mission could also help in studies about the origin of the Solar system. Asteroid Bennu is believed to have been born during the early stages of the solar system's origin.

Asteroid Bennu is said to have a high chance of colliding with earth. Scientists are working on measures to avoid any potential collision of the near-earth asteroids with the planet. The OSIRIS-REx mission to Bennu would help in developing better planet protection strategies.

NASA's Planetary Defence Coordination Office (PDCO) had been working on missions to find, track and characterize potential threats to Earth since 2016. The agency had been employing powerful supercomputers to produce stimulations of possible impacts using 3D modules of objects. It could help in developing strategies to assist plans and coordinate actions during emergency situations.

Telescopes like Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) has been used in identifying size, composition and other measures of the near earth objects. Astronomic agencies had been intensely studying recent encounters by near-earth objects which passed by earth.