They don't get much closer than 2007 GU1 will sometime tomorrow, April 16, 2007, when it passes approx. 2.1 times the distance from the Earth the Moon (Lunar Distance or LD, for short). It really makes one wonder, though, doesn't it, what with the prevelance of Near Earth Objects, that nothing serious has happened for millions of years. Well, if you exclude what happened in Tanguska back in 1908.

Nasa Link

Harvard Link

Awesome , totaly Awesome
thanks for the links
Radical , frillen outragious
Abecrombie

I hope no really big chunks go flying off.

What is surprising (and slightly scary) is how often asteroids come a lot closer to Earth than this. 2.1 LD = about 806,000 km (500,000 miles).

Over the last few years several asteroids have come consideranly closer that this. A list of some of them, with distances and a link to the BBC News story on the object below:

2002MN. Closest approach 120,000 km (75,000 miles) or 0.31 LD on 14^th June 2002. Asteroid size 50 - 120m. LINK.


2002 NY40. Closest approach 530,000 km (330,000 miles) or 1.4 LD on 19^th August 2002. Asteroid size aprox 800m. LINK.


2003 SQ222. Closest approach 88,000 km (54,700 miles) or 0.23 LD on 27^th September 2003. Asteroid size aprox 4 - 8m. LINK.

2004 FH. Closest approach 43,000 km (26,700 miles) or 0.11 LD on 18^th March 2004. Asteroid size aprox 25m. LINK.

2004 XP14. Closest approach 432,709 km (268,873 miles) or 1.1 LD on 18^th March 2004. Asteroid size aprox 25m. LINK.




Who says it hasn't?

Impacts which cause global devestation such as the Chicxulub event which most scientist believe kead to the extinction of the dinosaurs 65 million years ago require a large asteroid. In the case of Chicxulub the impacting body was around 10km (6 miles) across. Such large NEOs are very rare indeed and you would expect such an event only every few million years.

Smaller impacts are more common. The famous Meteor Crater (or Barringer Crater) in Arizona is only 50,000 years old.

Most smaller bodies burn up in the atmospere. Of those that don't most will explode in the upper atmosphere. Slightly larger objects will make it to the lower atmosphere (as did the Tunguska object). These objects would leave no crater and so most would simply go unrecorded. Any that occured in societies withour a written language would also go unrecorded. Smaller craters are likelt to be erased fairly quickly by weathering events. Add to this the fact that the Earths surface is mostly covered with water and it becomes clear that we simply will not have a record of must of these events.

To go along with Waspies post, I remember hearing that a Tunguska class object hits the Earth every seventy to a hundred years on average. Technically, we are over due.

The best description I've heard so far is that: "we live in a cosmic shooting gallery". Let's just hope that the cosmic gunner is a poor shot!

The truth is that we (Earth that is) are in a literal cosmic "shooting gallery". What we need is one of these nifty gravitational tractors. One bad strike could really ruin it for us...the only good option is to be pro-active.