NASA scientists say the Mars rovers have found what they were looking for — hard evidence that the red planet was once “soaking wet.”
“We have concluded the rocks here were once soaked in liquid water,” said Steve Squyres of Cornell University. He’s the principal investigator for the science instruments on Opportunity and its twin rover, Spirit.
“Three and a half years ago, in July 2000, we were on stage here to talk about sending two rovers to get evidence of past water. NASA and its international partners have turned those dreams to reality,” said Ed Weiler, NASA associate administrator for space science.
Scientists used instruments on board the golf cart-sized rovers to study the composition of the rocks and soil on the planet. The rocks’ physical appearance, plus the detection of sulfates, make the case for a watery history, and more important, an environment that could have been hospitable to life.
Spirit and Opportunity were sent to opposite sides of the planet with the possibility of investigating different types of terrain. Spirit, the first rover to arrive on January 3, landed near the Gusev Crater, which may once have held a lake.
But geologists and other researchers at NASA’s Jet Propulsion Laboratory in Pasadena, California, were thrilled when they saw the possibilities surrounding Opportunity, which landed three weeks later. It landed inside a small crater in the Meridiani Planum, one of the flattest places on the planet. And its landing site was within driving distance for the spacecraft to reach an exposed slice of bedrock.
Since its landing January 25, Opportunity has used the same tools as a human field geologist would to determine the chemical contents of the rocks. Using an alpha particle X-ray spectrometer, a device that can identify chemical elements, scientists have identified a high concentration of sulfur in the bedrock.
Another instrument on board, a Moessbauer spectrometer, has detected an iron sulfate mineral known as jarosite. From their knowledge of rocks on earth, scientists say rocks with as much salt as this Mars rock either formed in water, or had a long exposure to water after they were formed. The scientists say these rocks could have formed in an acidic lake or even a hot springs.