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... what are Apollo asteroids?

These objects are near-Earth asteroids whose orbits cross that of Earth. The group is named after asteroid 1862 Apollo which was discovered in 1932 by Karl Wilhelm Reinmuth (1892-1979), a German astronomer who is credited with the discovery of over 400 other asteroids.

Asteroid 1862 Apollo has a diameter greater than 150m and has its own moon, a smaller planetoid about 80m across, designated S/2005 (1862) 1.

Apart from Earth, asteroid 1862 Apollo also crosses paths with Venus and Mars. In the year 2075, it is calculated that it will pass a mere 1,240,000 km (or 770,000 miles) from Venus, a distance which in astronomical terms is very small.

Earth is no stranger to close, or catastrophic, encounters with asteroids. For example, asteroid impacts are believed to have caused mass extinctions at various times in our planet’s history. And as recently as February 15, 2013, a meteor exploded over Chelyabinsk, Russia, causing over a thousand casualties. It is thought that it was a member of the Apollo Group of near-Earth asteroids.

Thousands of near-Earth asteroids have been discovered and their trajectories plotted. Both NASA and JAXA (Japan Aerospace and Exploration Agency) currently have plans to send spacecraft to Apollo Group targets, to understand better their formation and composition; assess the hazard they pose to Earth; and to retrieve pristine samples of their regolith, or soil.

NASA’s mission is called OSIRIS-Rex: Origins, Spectral Interpretation, Resource Identification and Security, Regolith Exploration. Its target is asteroid 101955 Bennu. OSIRIS-Rex is to be launched in September 2016, and arrive at Bennu in 2018. If the mission is successful, the asteroid sample will be returned to Earth in 2023.

The target asteroid of JAXA’s mission is called Ryugu, formerly designated 1999 JU3.

The JAXA spacecraft for this mission is called Hayabusa 2. In Japanese, hayabusa means peregrine falcon, a bird of prey epitomizing speed, agility and precision.

Expected launch = 2018
Return to Earth = 2020

Related links:

Chelyabinsk Meteor

Chelyabinsk Meteor, Russia