"In one sense, this is an utterly surprising result—it's the number that everybody expected," Farley says.
Indeed, prior to Curiosity's geochronology experiment, researchers using the "crater counting" method had estimated the age of Gale Crater and its surroundings to be between 3.6 and 4.1 billion years old.
"That gives us some idea about why the environment looks like it does and it gives us an idea of where to look for rocks that are even less exposed to cosmic rays," and thus are more likely to have preserved organic molecules, Farley says.
Curiosity is now long gone from Yellowknife Bay, off to new drilling sites on the route to Mount Sharp where more dating can be done.
To provide an answer for how the geology of Yellowknife Bay has changed over time, Farley and his colleagues also designed an experiment using a method called surface exposure dating.The work, led by geochemist Ken Farley of the California Institute of Technology (Caltech), could not only help in understanding the geologic history of Mars but also aid in the search for evidence of ancient life on the planet.Many of the experiments carried out by the Mars Science Laboratory (MSL) mission's Curiosity rover were painstakingly planned by NASA scientists more than a decade ago. Keck Foundation Professor of Geochemistry and one of the 29 selected participating scientists, submitted a proposal that outlined a set of techniques similar to those already used for dating rocks on Earth, to determine the age of rocks on Mars.However, shortly before the rover left Earth in 2011, NASA's participating scientist program asked researchers from all over the world to submit new ideas for experiments that could be performed with the MSL's already-designed instruments. Findings from the first such experiment on the Red Planet—published by Farley and coworkers this week in a collection of Curiosity papers in the journal —provide the first age determinations performed on another planet.The paper is one of six appearing in the journal that reports results from the analysis of data and observations obtained during Curiosity's exploration at Yellowknife Bay—an expanse of bare bedrock in Gale Crater about 500 meters from the rover's landing site.