The Missing Craters of Asteroid Itokawa
			
		
		
		
			Where are the craters on asteroid Itokawa?  No one knows.  
The Japanese robot 
probe Hayabusa recently 
approached the 
Earth-crossing asteroid and is 
returning pictures showing a surface unlike any other 
Solar System 
body yet photographed -- a surface possibly devoid of 
craters.  
One possibility for the lack of 
common circular indentations is that 
asteroid Itokawa is a 
rubble pile -- a bunch of rocks and ice chunks only loosely held together 
by a small amount of gravity.  
If so, craters might be filled in whenever the 
asteroid gets jiggled by a passing planet -- 
Earth in this case.  
Alternatively, surface particles may become 
electrically charged by the Sun, levitate in the 
microgravity field, 
and move to fill in craters.  
Over the weekend, 
Hayabusa lowered itself to the surface of the 
strange asteroid in an 
effort to study the unusual body and collect surface 
samples that could be returned to Earth in 2007.