It is astronomy’s most notorious asteroid. Its big. It’s solid. And, in less than five years, Apophis – the “God of Chaos” – will come especially close to Earth.
It won’t hit.
However, it didn’t always seem that way.
When it was first discovered in 2004, initial orbit calculations for asteroid 99942 Apophis placed Earth in a collision “danger zone” during its 2029 and 2036 transits.
Apophis is a pile of rocks about 350 meters wide. That’s roughly the size of a modern luxury cruise liner, or one of America’s large nuclear-powered aircraft carriers.
If it hit the ground, it could destroy an area the size of a country. An impact at sea would cause a devastating tsunami.
But additional observations and radar deployments have since refined its orbital projections considerably.
We now know that, on April 13, 2029, it will miss Earth by 32,000 kilometers.
And the math is good enough to rule out any risk for another 100 years.
But the geostationary satellites that power the GPS on your cell phone are 35,800 km away. And the Moon is 384,400 km away.
So, cosmically speaking, Apophis will still be a very close call.
That’s why the European Space Agency (ESA) wants to look good as it catapults.
The menacing asteroid named Lord of Chaos
Apophis is named after the ancient Egyptian God of darkness and chaos – a god who constantly fought with Ra (the Sun God).
ESA wants to send RAMSES – named after the priest-king Pharaohs of Egypt – to intercede on behalf of humanity. (It’s also short for Apophis Fast Space Security Mission).
Part of the Planetary Defense Program, the mission is to better understand the composition and behavior of the more than 1,000 “planet killer” asteroids known as cannonballs in Earth’s orbit.
And the short notice (four years is the minimum for a space project) is not entirely accidental.
ESA presents the challenge as a “best practice” for a possible real-world scenario.
Astronomers believe that about 95 percent of all “planet-killing” asteroids have been found. It’s the missing 5 percent that worries them.
One can come out of nowhere, at any time. The odds of such an impact are a roll of the dice.
About 1.4 million asteroids have been found floating around the solar system. Most are joined between the orbits of Mars and Jupiter.
But some have fallen into more extreme trajectories, sending them hurtling toward the Sun — through the orbits of the inner planets, including Earth.
A review of all known threatening asteroid orbits has recently been completed.
“Good news,” says astronomer Oscar Fuentes-Muñoz of the University of Colorado Boulder. “As far as we know, there is no impact in the next 1,000 years.”
However, this only applies to large “planet killer” asteroids. Others – like Apophis – still have the potential to vaporize an area several hundred kilometers wide.
According to the Planetary Society, that would be the equivalent of 1,000 megatons, or hundreds of nuclear warheads all launched at the same place.
What danger do asteroids pose to Earth?
Earth passes through about 10 tons of interplanetary dust every day. These are the meteors you see almost every night.
Some, ranging in size from pebbles to bowling balls, enter the atmosphere three or four times each day. These cause the brightest flashes in the night sky.
Something the size of a truck arrives two to three times every century. The latest hit in 2013 – the massive fireball that shattered windows and injured pedestrians over the city of Chelyabinsk, Russia.
The big ones – about 150 meters wide – are potentially devastating. But the odds of one entering the atmosphere are about one in 25,000 years.
An impact from something over 1km in size could end civilization as we know it through tsunamis, fireballs and huge clouds of debris being shot up into the atmosphere. The chances of one of them arriving is once in two million years or so.
The dinosaur killer that struck 66 million years ago is believed to have been about 10 km across.
“Nature brings us one”: asteroid expert
To accelerate the RAMSES mission, ESA proposes to reuse the basic design of an asteroid mission already in the pipeline.
The Hera probe will launch in October. Its task is to review the double asteroids Didymos and Dimorphos, the subjects of an impact experiment in 2022.
RAMSES would take advantage of Apophis’s close pass to get a good look at how his stony surface is put together. And this means that the consequences of the asteroid’s close encounter with Earth’s gravity can be observed.
“For the first time ever, nature is bringing one to us and performing the experiment itself,” said ESA astronomer Patrick Michel.
NASA’s OSIRIS-REx probe (Osiris is the Egyptian god of the dead) recently sent samples of the asteroid Bennu back to Earth. It is now making its way through space to rendezvous with Apophis about a month after it passes Earth in 2029. It is expected to stay nearby for more than a year.
One of its missions will be to blast the surface of Apophis with one of its thrusters.
“This will allow us to observe subsurface material, which will provide unattainable insight into space weather and the surface strength of rocky asteroids,” say the University of Arizona mission planners.
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