NASA’s twin Mars rovers Spirit and Opportunity are currently studying the rims of their respective craters in preparation for what mission planners expect to be an extended science run on the red planet.

The last time NASA promised something like this involving Mars, the result was the revelation that the Opportunity rover’s landing site had once been soaked with water, providing the first evidence gleaned from the surface for past liquid water on Mars. A spokesperson for NASA told SPACE.com that the big announcement would again involve a discovery by the Opportunity rover and not its twin, Spirit. The agency did not provide detail regarding the science involved, and the spokesperson would not elaborate.