The mineral-filled fissures looked similar to those found in rocks in the Sahara, says Nicolas Mangold, a researcher with the Laboratoire de Planétologie et Géodynamique de Nantes in France and a member of the Curiosity rover's ChemCam team. Those desert veins were formed when water circulated through the cracks.
Given the conditions under which calcium sulfate forms on Earth, he suggests the veins on Mars formed at low to moderate temperatures.
The estimate hints at why the team is excited not just to have found evidence of water, but water that bears the raw material for precipitation of minerals. Like sedimentary rocks, minerals are made of bits and pieces from somewhere else – in this case from ions released from rock somewhere else as water flowed over or through it. And different minerals precipitate out at different temperatures, yielding some information about the environment at the time the minerals formed.
As Curiosity explores Yellowknife Bay, it will undergo its last test – using a drill at the end of its arm to extract the first drill samples. Those samples will be used to clean the delivery system the drill uses to transfer the samples to a pair of chemistry labs inside Curiosity's chassis. Once the cleaning ends, the drill will provide samples to the labs for analysis.
Researchers have selected a rock named for the late John Klein, Curiosity's former deputy project manager, who passed away in 2011. Drilling should begin within the next two weeks.