So what did Opportunity turn up?

http://www.space.com/scienceastronomy/opportunity_announcement_040322.html

NASA will announce a “major scientific finding” from its Mars rover mission on Tuesday, March 23 at 2 p.m. ET, the agency said in a statement.

Standing water on the surface. Not now, of course, but previously.

Probably doesn’t sound like much to the average person, but in terms of planetary science, this is a whopper of a discovery.