Mars Rover Findings: Red Planet Was Soaked

LOS ANGELES -- The Mars rover Opportunity has discovered that potentially life-sustaining waters once soaked the surface of Mars, providing an answer to one of the most provocative questions of modern planetary science.

At a news conference Tuesday in Washington, National Aeronautics and Space Administration scientists said that an analysis of rock samples showed that salt-laden sediments were shaped by percolating or flowing water -- and may even have been formed by a great Martian sea.

"Opportunity has landed on an area of Mars where liquid water once drenched the surface," said Ed Weiler, NASA's associate administrator of space science. "This area would have been a good, habitable environment for some period of time."

He called the findings "a giant leap" toward determining whether life may have existed on Mars during a warmer and wetter time in the now frigid planet's past.

Steve Squyres, a Cornell University geologist and chief scientist for the mission, said one of the key pieces of evidence was the discovery of dense deposits of sulfates -- similar to Epsom salts -- in an outcropping of bedrock near its landing site.

The mineral is typically left behind by receding groundwater or the evaporation of a salty lake or ocean.

Scientists used a grinding tool to look beneath the surface of the rock to be sure the salty deposits were more than a shallow crust. They then used an instrument called the alpha particle x-ray spectrometer that shoots radioactive particles at mineral atoms to determine their mass and composition.

The rocks were found to be "full of sulfate salts," up to 40 percent of the total mass of the rocks, said Squyres -- "a telltale sign, we believe, of water."

Squyres said several other several findings confirmed their assumptions.

The layered, scarred face of a rock the scientists have been studying -- nicknamed El Capitan -- could have been shaped by wind or water. But a striated pattern called "crossbedding" included concave patterns typically caused by the crest lines of underwater ridges.

The rover's panoramic camera and microscopic imager captured a number of randomly placed, pock-mark indentations, each a fraction of a centimeter long. The pattern typically forms when salt crystals grow within rocks sitting in briny water. When the crystals later dissolve or erode away, they leave holes like those seen on the El Capitan.

Pebble-like structures the scientists nicknamed "blueberries," embedded in the rock the way berries are embedded in a muffin, could have been formed by volcanic eruptions or by the violent force of a meteor impact. But scientists concluded that they were more likely "concretions," structures created from mineral deposits emerging from a watery solution inside the rock formation.

This combination of signs convinced the rover team that water must have been the unifying basis for the rock's characteristics.

"You work so hard on something," said Matt Golombek, a geologist at the Jet Propulsion Laboratory in Pasadena, California, who led the site-selection process and hit the jackpot. "You dream about it, but it was almost too much to hope for."