On April 13, 2029, a small 340-metre-wide (1,100-foot-wide) asteroid known at 99942 Apophis will pass within a scant 31,000 kilometres (19,000 miles) of Earth in what amounts to a near miss at astronomical scales, well inside the orbits of communications satellites.
Scientists can’t wait.
During a 30 April meeting at the 2019 Planetary Defense Conference in College Park, Maryland, researchers reviewed plans to observe the asteroid and discussed possible missions that might be sent to inspect the body at close range.
“The Apophis close approach in 2029 will be an incredible opportunity for science,” said Marina Brozović, a radar scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’ll observe the asteroid with both optical and radar telescopes. With radar observations, we might be able to see surface details that are only a few meters in size.”
From Earth, the asteroid will provide a special treat for amateur astronomers and the public at large, growing as bright as stars in the Little Dipper and at one point moving more than the width of the full Moon in less than a minute.
According to a JPL press release, “the asteroid, looking like a moving star-like point of light, will first become visible to the naked eye in the night sky over the Southern Hemisphere, flying above Earth from the east coast to the west coast of Australia.
“It will then cross the Indian Ocean, and by the afternoon in the eastern U.S. it will have crossed the equator, still moving west, above Africa. At closest approach, just before 6 p.m. EDT, Apophis will be over the Atlantic Ocean – and it will move so fast that it will cross the Atlantic in just an hour. By 7 p.m. EDT, the asteroid will have crossed over the United States.”
Apophis was discovered in June 2004. Lost and then recovered later that year, analysis of its path initially indicated a 2.7 percent chance of an Earth impact in 2029. Additional observations ruled that out, but it still has a small, less than 1-in-100,000 chance of hitting Earth many decades from now.
“We already know that the close encounter with Earth will change Apophis’ orbit, but our models also show the close approach could change the way this asteroid spins, and it is possible that there will be some surface changes, like small avalanches,” said Davide Farnocchia, an astronomer at JPL’s Center for Near Earth Objects Studies.
Paul Chodas, director of CNEOS, said Apophis is one of about 2,000 known Potentially Hazardous Asteroids, or PHAs.
“By observing Apophis during its 2029 flyby,” he said, “we will gain important scientific knowledge that could one day be used for planetary defence.”