17 October 2009: Asteroid 2009 TM8 to fly by the Earth today, within the orbit of the Moon

Nice, a new asteroid! The discovery of asteroid 2009 TM8 was discovered just Thursday, so only a few days before closest approach. One reason for this is size as it is a mere 7 metres in diameter (if it hit Earth it would just burn up in the atmosphere), but often asteroids that come from the direction of the Sun are also late to be discovered due to the glare.

The orbit can be seen on the right - it's a fairly close one and quite comparable to that of Mars but just a bit lopsided. An asteroid of this size could one day be an interesting candidate to be moved into Earth orbit in order to be mined, because at a mere 7 metres in diameter it would pose no danger to the planet even if a mistake were to be made, while 7 metres still makes for a fair amount of material - 179 cubic metres of material. With a density of 2 grams per cubic centimetre this would make for a total mass of 360,000 tons.

As for the explosive force of this asteroid if it were to hit - it would result in a 4 kiloton explosion in the atmosphere, which really isn't much at all. Little Boy (the bomb dropped on Hiroshima) had a blast yield of 13-18 kilotons, and that was dropped over the centre of a city as opposed to way up in the atmosphere likely in the middle of nowhere, and also without radiation as well.