"Unknown silvery substance" just sounds ominous...but cool!
Thanks for the links, I'm going to go check those out!
Cuhail
[edit on 10/1/2008 by Cuhail]
The second flyby is expected to yield even more surprises. A laser altimeter on the spacecraft will measure the planet's topography, allowing scientists, for the first time, to correlate high-resolution topography measurements with high-resolution images. At the same time, MESSENGER's sensors will analyze the chemical and mineralogical composition of Mercury's surface.
The two craters at the bottom of the frame are located in Mercury's giant Caloris Basin, a thousand mile wide depression formed billions of years ago when Mercury collided with a comet or asteroid. For scale, the larger of the two is about 40 miles wide. Both craters have dark rims or "halos" and the one on the left is partially filled with an unknown shiny material.
MESSENGER encountered Mercury's sodium-rich exospheric "tail" which extends more than 25,000 miles from the planet and also discovered a hydrogen tail of similar dimensions.
Turning to Mercury's magnetic field, MESSENGER found it to be different compared to Mariner 10 observations 30 years ago. While the magnetic field was generally quiet (no magnetic storms) on Jan. 14th, it showed several signs of significant internal pressure. Additional flybys by MESSENGER in late 2008 and 2009 plus a yearlong orbital phase beginning in 2011 will shed more light on the stability and dynamics of Mercury's magnetic cocoon.

