This is the latest being reported from NASA.

Key quote:

"There are high expectations that we will understand the extent to which the outcrop has been modified chemically and whether water was involved," Ray Arvidson, deputy principal investigator, said. Arvidson said scientists are working on competing theories about how the fine layers in the 3 foot-high outcrop were formed, and hoped to have preliminary findings within days. "One idea is that it's associated with ash fall or simply windblown material that was compacted," he said. "Or it's associated with (sedimentation in) an old lake or shallow sea. The hope is in the end you have the information to show how they were formed and modified."

"competing therories"...really? If I know geologists, these have got to be some interesting conversations!