Here is a bit more information on what they are looking for in their decision process:

The petrified sand dunes were discovered amongst an area of dark sandstone along a ridge at the lower slope of Mars’ Mount Sharp. They are now being explored in detail by the six wheeled rover in a geologic feature dubbed the Stimson unit.

“The team is considering where to drill next within the Stimson sandstone and we are looking for the best light toned areas to check for mineralogical signs of water-rock reaction,” says John Bridges, rover team member from the University of Leicester, England, in the latest mission update from today, September 12, 2015.

What do you think they will find?  And what if they found fossils?  That would change things in an incredible way.

thanks to universetoday.com for the great info

thanks to NASA for the pic