The spherules.
There is some debate on whether the spherules seen at the Opportunity site are blue or grey.
Below is a color image I composed from the red, green, blue filter images.
I don't like the color of the NASA logo - the blue is too dark and the red arrow through it should be more visible.
Here are the links for the red, green, blue filter images if someone wants to try adjusting the combinations to get a better image:
Red filter image.
http://marsrovers.jpl.nasa.gov/gall...0P2549L4M1.HTML
Green filter image.
http://marsrovers.jpl.nasa.gov/gall...0P2549L5M1.HTML
Blue filter image.
http://marsrovers.jpl.nasa.gov/gall...0P2549L6M1.HTML
Bob Clark