Oh, please be footprints or fossils, please be footprints or fossils...
Seriously, the big news - "This data is gonna be one for the history books" - is apparently the result of work done with the SAM lab on the rover, so it's probably just interesting chemistry - organic molecules maybe. Yeah, that's cool. No really, it's very nice. We should be grateful. Thank you. I mean what else could we possibly expect?
Not Tharks. It's never Tharks...
UPDATE: NASA sez "Not So Fast!"
Rumors and speculation that there are major new findings from the mission at this early stage are incorrect. The news conference will be an update about first use of the rover's full array of analytical instruments to investigate a drift of sandy soil. One class of substances Curiosity is checking for is organic compounds -- carbon-containing chemicals that can be ingredients for life. At this point in the mission, the instruments on the rover have not detected any definitive evidence of Martian organics.
The Mars Science Laboratory Project and its Curiosity rover are less than four months into a two-year prime mission to investigate whether conditions in Mars' Gale Crater may have been favorable for microbial life. Curiosity is exceeding all expectations for a new mission with all of the instruments and measurement systems performing well. This is spectacular for such a complex system, and one that is operated so far away on Mars by people here on planet Earth. The mission already has found an ancient riverbed on the Red Planet, and there is every expectation for remarkable discoveries still to come.
For more information about NASA's Curiosity mission, visit: http://mars.jpl.nasa.gov/msl
Not even organics...peh!