About 5-1/2 years from now, astronomers predict, an asteroid about as wide as the Empire State Building is tall will streak through space within 20,000 miles (32,200 km) of Earth, the closest any celestial object of that size will have come to our planet in modern history.
When it does, a spacecraft launched by NASA in 2016 is expected to be in position to provide a detailed examination of this rare close encounter.
The mission, directed by University of Arizona scientists, is expected to yield insights into planetary formation and knowledge that could inform efforts to build a defense system against possible doomsday asteroid collisions with Earth.
At the time of its 2004 discovery, the asteroid Apophis, named for a demon serpent embodying evil and chaos in ancient Egyptian mythology, appeared to pose a dire impact threat to Earth, with scientists forecasting a potential collision in 2029. Refined observations have since ruled out any impact risk for at least another century.
Still, its next approach in 2029 will bring the asteroid within a cosmic cat’s whisker of Earth – less than one-tenth the moon’s distance from us and well within the orbits of some geosynchronous Earth satellites.
The spacecraft now headed for a rendezvous with Apophis is OSIRIS-REx, which made headlines plucking a soil sample from a different asteroid three years ago and sending it back to Earth in a capsule that made a parachute landing in Utah in September.
Rather than retire the spacecraft, NASA has rebranded it as OSIRIS-APEX – short for APophis EXplorer – and fired its thrusters to put it on course for its next target.
The Apophis expedition was detailed in a mission overview published in the Planetary Science Journal.
Apophis, oblong and somewhat peanut-shaped, is a stony asteroid believed to consist mostly of silicate materials along with iron and nickel. Measuring about 1,110 feet (340 meters) across, it is due to pass within about 19,800 miles (31,860 km) of Earth’s surface on April 13, 2029, becoming visible to the naked eye for a few hours, said Michael Nolan, deputy principal investigator for the mission at the University of Arizona.—INP
