for National Geographic News
NASA scientists said Tuesday that the roving robot Opportunity has found evidence that water once soaked the planet Mars.
Liquid water is the one absolute requirement for life on Earth. Although the discovery does not mean the evidence of life on Mars has been found, it suggests that life could have evolved there at one point just as it did on Earth.
The discovery may have laid to rest one of the most vexing questions in planetary science: whether Mars was once capable of sustaining some form of life.
But it has also prompted a plethora of new questions.
"If liquid water existed on Mars, did life develop there? What is required to form life? How unique is life on Earth?" said Matt Golombek, a geologist at the Jet Propulsion Laboratory in Pasadena, California, who was in charge of choosing the landing sites for the two rovers. "These are compelling questions that we can begin to address with a Mars exploration program."
The Mars mission was specifically launched to check if Mars ever had a persistently wet enough environment to host life. By landing the rover Opportunity next to an exposed slice of bedrock on the inner slope of a small crater in the Meridiani Planum region of Mars, the scientists hit the jackpot.
Pictures from the rover's panoramic camera and microscopic imager of the target rock, dubbed "El Capitan," revealed salt-laden sediments that would have been shaped by flowing water or maybe even a great Martian lake or sea.
The dense deposits of sulfates, which are similar to Epsom salts on Earth, are the key evidence that water once existed on Mars.
Pebble-like structures, which the scientists nicknamed "blueberries," were found embedded in the rock. The scientists have concluded that these were created from mineral deposits emerging from a watery solution inside the rock.
"Most of the evidence to date has been strongly suggestive, based on morphology, but perhaps not conclusive," said Golombek. "The evidence is in the chemistry and mineralogy [sulfates] and textural clues for thin bedding, relict minerals that have been dissolved away and the growth of concretions which requires liquid water."
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