OU on the BBC: Background Brief - Impact Planet Earth: The Story So Far

Used with permission

A DISASTER HEADING OUR WAY?

Used with permission 65 million years ago, a huge asteroid smashed into the Earth. While it may not have been solely responsible for the subsequent mass extinction - which included the dinosaurs - it certainly helped send the Earth’s ecosystem into a catastrophic tailspin which took millennia to recover from.

The statisticians say it’s not just probable an event like this could happen again, it’s inevitable.

Asteroids are rocky bodies which tend to live in orbits between Mars and Jupiter. Comets on the other hand are a mix of rock and ice and they can swing into the Earth’s orbit from anywhere in the Solar System. Comets have an icy tail which reflects the sun and can therefore be seen from Earth - if you’ve got the right telescopic equipment and are pointing in the right direction anyway. But asteroids have far less visibility and have to be at least half a kilometer across to be detectable. Used with permission

There are millions of potentially wayward bodies out there.

(image courtesy of NASA)
 
We know that these impacts have taken place throughout our Solar System for billions of years. For a graphic illustration, look at the Moon. Its surface is made up of literally layers of craters upon craters which have built up over time, in an undisturbed environment.

The Earth too is constantly being showered by debris.

Used with permission Cratering tends to be eroded on Earth by weathering and geological processes. But scientists believe they have found the remains of 150 craters - like Meteor Crater in the Arizona desert (right). It may look impressive, but it’s a tiny pockmark in the cosmic scheme of things ...

Did an asteroid kill the dinosaurs - and could another kill us?

Used with permission Despite what you may have heard, it hasn’t been proved that an impact was solely responsible for wiping out the dinosaurs. But the asteroid which created the impact feature at Chicxulub would certainly have had a massive effect on the environment, and a mass extinction did take place around the time.

Another impact of the same size would certainly have a global effect on civilisation to some extent.

Doom-mongers like to say we’re "overdue for another giant asteroid impact". But that’s just playing with figures. In fact we have no idea when the next one will be.... Because we haven’t spotted it yet.

So how can we protect ourselves?

Not many organisations are spending money on asteroid-detection or contingency plans, because a deathly impact is such a remote possibility. But some efforts are being made.

Used with permission (image courtesy of NASA)

- NASA has just launched a probe which will aim to gather more information about roving asteroids from studying them at close range.

- Spacewatch is international collaboration using observatories from around the world in co-ordinated detection of Near Earth Objects .

First broadcast: Friday 15 Oct 1999 on BBC TWO

Background Brief in more depth: