The bright red fingers of the Rio Tinto, an acidic river in southwest Spain, are seen in this aerial photograph. NASA scientists have made use of this uninviting landscape in the Mars Analog Rio Tinto Experiment (MARTE) to develop drilling and sample handling technologies that may be used in future explorations of Mars. Field researchers have already found that the Rio Tinto is full of extremeophile microbes that can thrive in the harsh iron- and sulfur-laden waters that are hostile to many organisms.