TheEuropean Space Agencyhas given the go-ahead for initial work on a mission tovisit an asteroidcalled (99942) Apophis.
Apophis is 340 metres wide, about the same as the height of the Empire State Building.
If it were to hit Earth, it would causewholesale destructionhundreds of miles from its impact site.
Luckily, Apophis wont hit Earth in 2029.
The impact of this asteroid brought about a global extinction event that wiped out the dinosaurs.
Located in the asteroid belt between Mars and Jupiter, asteroids come in many shapes and sizes.
Artist’s impression of Apophis.
The asteroid belt contains 1-2 million asteroids larger than a kilometre across and millions of smaller bodies.
There are 35,000 suchnear-Earth objects(Neos).
But detection is not enough; we have to find a way to defend Earth against an incoming asteroid.
Detail from Egyptian tomb showing great cat of Re killing the giant snake Apep (Apophis).
Blowing up an asteroid, as depicted in the movie Armageddon, is no use.
The asteroid would be broken into smaller fragments, which would keep moving in much the same direction.
Instead of being hit by one large asteroid, Earth would be hit by a swarm of smaller objects.
The preferred solution is to deflect the incoming asteroid away from Earth so that it passes by harmlessly.
To do so, we would need to apply an external force to the asteroid to nudge it away.
Apophis, Ramses, and Osiris-Apex
Apophiswas discovered in 2004.
The asteroid passed by Earth on December 21, 2004 at a distance of 14 million kilometres.
It returned in 2021, and will swing by Earth again in 2029, 2036, and 2068.
Until recently, there was a small chance that Apophis could collide with Earth in 2068.
These showed that Apophis would not hit our planetfor the next 100 years.
It will then accompany the asteroid as it approaches Earth.
It intercepted Bennu in 2020 to collect samples of rock and soil from its surface.
It dispatched the rocks in a capsule, which arrived on Earth in 2023.
Osiris-Apex will reach the asteroid just after its 2029 close encounter.
A close flyby of an asteroid as large as Apophis happens only once every 5,000 to 10,000 years.
To the ancient Egyptians, the Sun was personified by several powerful gods, chief among themRe.
The Suns setting in the evening was interpreted as Re dying and entering the netherworld.
Only after Apophis had been defeated could Re be revitalised by Osiris, the king of the netherworld.
Re could then once again be reborn in the east, rising in the sky once more.
But Apophis is always defeated, his body pierced by a spear or riven by knives.
