OSIRIS-APEX is a mission to study the physical changes to asteroid Apophis that will result from its rare close encounter with Earth in April 2029. That year, Apophis’ orbit will bring it within 20,000 miles (32,000 kilometers) of Earth’s surface — closer to Earth than our highest-altitude satellites. Our planet’s gravitational pull is expected to alter the asteroid’s orbit, change how and how fast it spins on its axis, and possibly cause quakes or landslides that will alter its surface. OSIRIS-APEX will allow scientists on Earth to observe these changes. Additionally, the OSIRIS-APEX spacecraft will dip toward the surface of Apophis – a “stony” asteroid made of silicate (or rocky) material and a mixture of metallic nickel and iron – and fire its engines to kick up loose rocks and dust. This maneuver will give scientists a peek at the composition of material just below the asteroid’s surface.
NASA / University of Arizona