Identifying chemical signatures from orbit is one thing, though... finding and studying actual outcroppings of phyllosilicates at ground level is something else entirely. And this is precisely what the MER team has been hoping Opportunity will do at Endeavour.
The first discovery of veins like this back in August raised their hopes.
"This is a real triumph of geology," said Steve Squyres, Mars Exploration Rover principal investigator at Cornell University. "We saw these veins as we crossed from the Meridiani plains into the Noachian terrain back in August. We've kept those in mind as a very important thing we wanted to look at, but we were so focused on getting into the Noachian and new terrain that we made that the highest priority, figuring that we would get the veins later."
It looks like "later" is now.
A closer look at Homestake with Opportunity's microscopic camera shows a bright surface gouged by linear scratches. This view, a composite of three separate images also by Stu Atkinson, gives a closer look: