NASA Spacecraft Will Visit Apophis, Once Earth’s Deadliest Asteroid Threat

It all began in the evening of June 28, 2004, when a small dot appeared in the sky over the Kitt Peak National Observatory in the mountains of Arizona. The dot was flagged as a possible newly discovered asteroid by Astronomer Bernardi and two of his colleagues. An object with a width of a few hundred meters was initially designated 2004 MN4 and is now estimated to be about 14 million kilometers from Earth.

The world would be shocked by a preliminary appraisal of the object. The asteroid had a one-in-37 chance of hitting Earth in 2029, according to analysis by NASA. It was the most dangerous asteroid discovered so far, because it was large enough to cause destruction.

There was no chance of Apophis impacting Earth for the next century. In 2029, the asteroid will come very close to us, swooping below the satellites. Apophis will be as bright as a satellite as it passes through our skies on April 13, 2029, visible to billions of naked-eye observers. When asked how many stargazers will be watching this amazing encounter, JPL's Marina Brozovic has a simple answer.

Apophis's close approach could offer more than eye candy. In 2029, scientists are hoping to rendezvous with an object. At least one visitor from our planet has been confirmed: NASA's OSIRIS-REx, which was launched in 2016 on a mission to collect samples from another asteroid, Bennu, and bring them back to Earth. OSIRIS-REx is currently on its way home from Bennu, and will be dropping off its samples in September of 2023. NASA approved a $200-million extension to the mission after the spacecraft continued flying through space. It is really exciting that OSIRIS-REx will rendezvous with Apophis.

After the close encounter with Earth, OSIRIS-APEX will perform initial research before entering the atmosphere around the object in August 2029. Mission scientists will look for any changes caused by Apophis's brief plunge through our planet.

pinning down the object's orbital motion to meter-scale precision is one of the important goals of the mission. This will allow researchers to work out Apophis's future trajectory and its threat to Earth. OSIRIS-APEX will greatly extend such forecasts, but how far into the future is not yet clear. The Yarkovsky effect is a phenomenon in which the sun's heating can change an asteroid's trajectory through space. The effects on Apophis will be measured by the spacecraft, as well as any changes in the asteroid's rotation. Nolan says that the measurements will allow scientists to see whether or not their ideas are correct and for how asteroids respond to external forces.

OSIRIS-APEX is not the only mission that will visit Apophis. A South Korean team has proposed a journey to the asteroid, with a spacecraft launching in 2027 and arriving in January 2029, before Apophis flies by. Smaller missions, such as Apophis Pathfinder, have been put forward as well. It is possible that some private astronauts could fly up to the asteroid to lay eyes on it.

At the end of OSIRIS-APEX's primary extended mission, the spaceship will approach Apophis and fire its thrusters from a few meters away. The asteroid's composition and structure will be revealed when the material is kicked up. The extendable arm is used to collect samples from Bennu, but mission planners say they have no plans to use it. DellaGiustina says that using the arm or even landing OSIRIS-APEX on the surface to act as a tracking beacon could become a viable option if NASA wants to extend the initial 18 months at Apophis. She says that if the spacecraft remains healthy, it could even move on to another asteroid.

Apophis poses no immediate threat to Earth. In 2029, it will fire a warning shot, followed by at least one inquisitive observer. Learning as much as we can about this object now rather than later, when the situation could be far more urgent, may be the best hope for avoiding some far-future catastrophe. We might be ready for the next one with OSIRIS-APEX's help.