God of Chaos Asteroid Apophis is Headed for Earth—and NASA is Excited

Apophis, NASA
This image shows the distance between the Apophis asteroid and Earth at the time of the asteroid's closest approach. The blue dots are the many man-made satellites that orbit our planet, and the pink represents the International Space Station. NASA/JPL-Caltech

On April 13, 2029, a 1,110-foot-wide asteroid known as 99942 Apophis will speed past our planet at an estimated distance of around 19,000 miles, potentially coming closer to the surface than some orbiting spacecraft.

Despite being a decade away, this future close encounter is causing quite a stir within the asteroid research community. So much so that it is the focus of a session Tuesday at the 2019 Planetary Defense Conference in College Park, Maryland, during which scientists will discuss everything from potential observation strategies to hypothetical missions that could explore the object itself.

"The Apophis close approach in 2029 will be an incredible opportunity for science," Marina Brozovic, a radar scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, who is chairing the meeting, said in a statement. "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."

The reason that scientists are so excited about Apophis, which is named after an ancient Egyptian god of chaos, is that asteroids of this size rarely pass by Earth at such a close distance.

Among the topics set to be discussed at the conference—aside from possible missions—are the potential effects of Earth's gravity on the asteroid and strategies to learn about the object's interior.

"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," Davide Farnocchia, an astronomer at JPL's Center for Near Earth Objects Studies (CNEOS), who is co-chairing the session, said in the statement.

On the day of the close approach, the asteroid will be visible to the naked eye, appearing like a moving star in the sky over the Southern Hemisphere. Beginning its journey above Australia, it will soar over the Atlantic Ocean in just an hour, before reaching the West Coast of the United States in the early evening. It is during this passage that scientists will be able to make the most important observations of the object—casting light on its size, shape, composition and possibly even its interior.

Apophis was first discovered in June 2004 by astronomers at the Kitt Peak National Observatory in Arizona, although the team was able to track the object for only two days because of technical and weather problems.

Later that year, an Australian group managed to spot the asteroid again. With their data, they estimated that the object had a significant 2.7 percent chance of colliding with the Earth in 2029. Fortunately, this prediction has been definitively ruled out.

Since the rediscovery, scientists have been tracking Apophis closely, and now it is believed that the object has a tiny chance of striking our planet many decades in the future.

"We have 15 years of optical and radar tracking data on Apophis and so we have a very precise estimate of its orbit through the 2029 encounter with the Earth," Farnocchia told Newsweek. The orbit of Apophis after the 2029 encounter has a higher degree of uncertainty, but one that will be reduced by tracking data collected during the next decade. While we cannot yet completely rule out a collision of Apophis after 2060, those chances are extremely small, less than 1 in 100,000."

This is fortunate because if an asteroid of such size were to collide with the Earth, it could cause devastation on a continental scale, although not a global extinction, according to Farnocchia.

Paul Chodas, director of CNEOS, said in a statement: "Apophis is a representative of about 2,000 currently known Potentially Hazardous Asteroids. By observing Apophis during its 2029 flyby, we will gain important scientific knowledge that could one day be used for planetary defense."

This article was updated to include additional comments from Davide Farnocchia.