A Salty Sea Long Ago Lapped on Surface of Mars, NASA Discovers
Portions of the Martian surface were once covered with an ancient salty sea, NASA scientists said Tuesday, announcing a discovery that transforms the image of the now-frigid and desolate planet.
Evidence of the body of water, possibly covering hundreds or thousands of square miles, was found near the landing site of the rover Opportunity in Meridiani Planum near the Martian equator. The rover has been exploring the planet since Jan. 24.
"The rocks at Meridiani were not only modified by water, they were actually formed in water," said Ed Weiler, NASA associate administrator for space science, at a news conference in Washington. "This is a profound discovery. It has profound implications for astrobiology.
NASA scientists announced earlier this month that they had determined that water had once existed on Mars, possibly during the early history of the planet 3 billion to 4 billion years ago. But they did not know if the water was percolating in underground reservoirs or actually flowed on the surface in lakes, rivers or seas.
They have now determined that the rocks at Meridiani Planum were formed in a standing body of water, long since evaporated from the desiccated landscape of towering canyons and rock-strewn craters.
Although the water may have been shallow, it was more probably "water you can swim in," and perhaps very deep, said Steve Squyres, a Cornell University geologist who serves as the mission's chief scientist.
The finding is the strongest evidence yet that Mars once had a habitable environment.
Matt Golombek, a mission geologist at the Jet Propulsion Laboratory in Pasadena, said the standing water means that portions of the Martian environment were once much warmer than today's frozen desert. The planet's atmosphere is likely to have been much denser, or the water would have evaporated rapidly, he said.
NASA gathered the new data about two weeks ago, then had the results reviewed by outside experts, all of whom concurred with the agency's conclusions.
"I was astonished to see structures like we see on Earth," said Dave Rubin, a geologist with the U.S. Geological Survey and one of the independent reviewers.
He compared the terrain to the salt-encrusted Qaidam Basin in central China. Other scientists said it resembled Death Valley, itself an ancient sea bed.
