AMERICAN space agency Nasa yesterday launched at 1.21am Eastern Standard Time a rocket called DART, which stands for Double Asteroid Redirection Test.
It is the world’s first full-scale mission to test technology for defending Earth against potential asteroid or comet hazards, and was launched aboard a SpaceX Falcon 9 rocket from Space Launch Complex 4 East at Vandenberg Space Force Base in California.
DART will travel for 10 months and 11m kms to a double asteroid to show, as Nasa stated, “that a spacecraft can autonomously navigate to a target asteroid and intentionally collide with it – a method of deflection called kinetic impact”.
They are targeting a near-Earth double asteroid known as Didymos and Dimorphos, with the latter being a “moonlet” estimated to be about 160 metres in size. It has been chosen because it is a good test object, and not one that is actually expected to collide with Earth.
Scientists estimate the kinetic impact will shorten Dimorphos’ orbit around Didymos by several minutes. Researchers will precisely measure that change using telescopes on Earth.
WASN’T THAT A MOVIE PLOT?
CLOSE. The 1998 film Armageddon featured a team of drillers landing on an asteroid heading for Earth and then blowing it up with a nuclear bomb.
By comparison, Nasa DART merely wants to land a gentle punch on Dimorphos to prove the deflection concept is viable.
DO WE REALLY NEED THIS MISSION?
THE cynics may say it is a huge and expensive – £250m – PR stunt by Nasa, but the chances of an asteroid hitting Earth are higher than you might think and the human species really does have to think about what to do if an asteroid collision becomes inevitable – and we should get plenty warning if that is going to happen.
Experts say that thousands of tiny particles strike the Earth every year, mostly burning up in the atmosphere as meteors, but some make it through and become meteorites if they land.
We know that very large meteorites, possible the remains of comets or asteroids, have struck the Earth before, most famously the impact which wiped out the dinosaurs 66 millions years ago and which goes by the catchy name of the Cretaceous–Paleogene (K–Pg) extinction event.
That event was caused by a comet or asteroid about six to nine miles wide landing somewhere around the Gulf of Mexico. As much as 75% of all species on Earth died as a result of the planet being effectively suffocated.
As recently as 2013 the Chelyabinsk Event in Russia saw a rock roughly the size of a six-storey building break up with massive explosions which had the force of approximately 20 to 30 Hiroshima bombs, injuring 1200 people and causing around £25m worth of damage. But that event was very rare, and there are no records of anyone other than one American woman being struck by a meteorite.
On November 30, 1954, Ann Hodges was injured by a meteorite that crashed through the roof of her home in Sylacauga, Alabama. It struck a radio, and then hit Hodges on her hip.
Michael Reynolds, a Florida State College astronomer and an author on a book about meteorites, states: ”You have a better chance of getting hit by a tornado and a bolt of lightning and a hurricane all at the same time.”
Good odds, then.