The enormous asteroid set to skim the Earth in 2029

NASA has revealed the real-life inspiration behind a role-playing exercise being carried out this week, in which a massive asteroid is detected coming straight for Earth.

2019 PDC is a fictional asteroid, the subject of a drill taking place this week at the 2019 IAA Planetary Defence Conference to figure out how scientists might react and work together to defend the planet.

While the hypothetical asteroid is scheduled to hit in 2017, there's a real one set to make a pants-wettingly-close flyby in 2029.

It's called 99942 Apophis, and is 340m wide - considerably bigger than the fictional 2019 PDC, and about the size of Mt Eden. When it was first discovered in 2004, it was estimated to have a 1 percent chance of smacking into Earth in 2029.

Scientists now believe it'll skim by 31,000km from the ground.

"That's within the distance that some of our spacecraft that orbit Earth," NASA said in post on its Solar System Exploration page.

"It's rare for an asteroid of this size to pass by the Earth so close. Although scientists have spotted small asteroids, on the order of 5-10 metres, flying by Earth at a similar distance, asteroids the size of Apophis are far fewer in number and so do not pass this close to Earth as often."

It's estimated asteroids as big as Apophis hit the Earth once about every 80,000 years.

The asteroid in the fictional scenario this week is 200m across, and would hit with the power of 34,000 Hiroshima-strength atomic bombs. A graphic posted by the European Space Agency on Twitter showed it would be strong enough to destroy most of a large city like Denver, Colorado.

Apophis is about five times bigger in volume, and is being discussed at the conference.

"The Apophis close approach in 2029 will be an incredible opportunity for science," said NASA radar scientist Marina Brozovi.

"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 metres in size."

There is a chance, however, Apophis' close run-in with Earth in 2029 could change its orbit, putting it on track for a future showdown with our planet.



NASA is considering launching a probe to visit it close-up.

"Apophis is a representative of about 2000 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 defence," said Paul Chodas, director of NASA's Center for Near Earth Objects Studies.