Thursday, April 11, 2013

Henry Spencer - Asteroids: What (Little) We Know, How Much We Don't, And How To Fix That

Henry Spencer started with the history of asteroids.  We now know of about 200,000 asteroids.  There are a bunch between Mars and Jupiter.  We have long known of the asteroids at the trojan points for Jupiter.  There may be more asteroids in the trojan poinnts than in the asteroid belt.  There are also a few asteroids at the trojan points for Mars.

There are many near Earth.  The biggest one found so far which comes close to earth is four and a half kilometers.  It appears some of the moons of other planets are captured asteroids. 

Comets are also worth mentioning.  There are short period comets which come regularly.  The long period comets come around every couple million years.  Current thought is short period comets were long period comets which got affected by Jupiter.  There are giant comets, some 200 km across. 

There is a comet which may hit Mars next year. People think there is a chance of one in 8000.  It appears to be about 20 km across.

They have found "asteroids" which are made up of comet stuff.  Now thought that about 15% of asteroids are burned out comets.

It appears Jupiter disrupted any possible formation of a planet between Mars and Jupiter. 

Ceres may have more fresh water than earth!!!  We should know more in a couple years.

Best guess is there are about a thousand near earth asteroids over a km and millions in the smaller sizes.

We are using optical and radar to gather information about asteroids.  We have done space craft visits for a few asteroids.  Most of those are quick fly bys.  Quick fly bys give little information. 

The orbit and spin of asteroids are affected by sunlight.

There is some evidence that many asteroids are what is called "rubble pile" asteroids.  This is basically collection of rocks held together by their own gravity.

There are a lot of puzzles still left.

To really understand asteroids we need more ground searches and orbiters.  To do effective prospecting we'll need lots of cheap spacecraft.

The full agenda for Space Access 2013 agenda.

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