And then there were two: Gale and Eberswalde craters.
Without any fanfare, NASA on Wednesday quietly mentioned on its Web site that the target destination for Curiosity, the $2.5 billion roving science laboratory, had been narrowed to two finalists. Gale Crater contains ancient lakebed deposits and, in its middle, a 5-kilometre-tall layered mound of rock; while Eberswalde is expected to hold a relic river delta, which would have the potential to preserve organic materials. The decision means the end for Mawrth Vallis and Holden Crater, the other two finalist sites.
But the decision also means that, so far, officials at NASA headquarters are agreeing with the recommendations of the Curiosity science team, which had ranked Gale just ahead of Eberswalde in a secret vote.
NASA officials have said that the final decision would come no earlier than 11 July. Science chief Ed Weiler, who will make the final call, had directed a council of top NASA officials to study the site selection process further after the mission team made presentations to the council on 24 June. The announcement on the Web site today says that a final decision is expected this month.