Washington, March 3: Water is the elixir of life, and scientists reported almost certain evidence that the tiny crater that holds the Mars rover Opportunity was once soaked in it.
The finding greatly increases the likelihood that Mars was a much more hospitable planet early in its history, possibly even amenable to the rise of life.
The scientists do not know what kind of wet environment existed at the Opportunity landing site: perhaps groundwater percolating up through volcanic ash, perhaps a lake bed that dried up, perhaps something else.
Nevertheless, “we believe at this place on Mars for some period in time, it was a habitable environment,” said Steven W. Squyres, a professor of astronomy at Cornell and the principal investigator for the mission.
“This is the kind of place that would have been suitable for life,” he went on, but quickly added: “Now that doesn’t mean life was there. We don’t know that.”
Squyres said he could not say when the area had been wet or how long it remained that way, except that the period was not recent. While ice still exists near the poles, most of Mars, including the equatorial region where the Opportunity set down, is devoid of water, liquid or frozen.
To highlight the significance of the findings, Nasa did not hold Tuesday’s news conference at the jet propulsion laboratory in California’s Pasadena, where the scientists have been working, but flew them to the Nasa headquarters in Washington.
“Our ultimate quest at Mars is to answer the age-old question, ‘Was there life, is there life on Mars'’” Edward J. Weiler, the agency’s associate administrator for space science, said. “Today’s results are a giant leap toward achieving that long-term goal.”
The mission of the two rovers Nasa landed on Mars in January is to search for signs of past water. At least in a small crater on the plains of Meridiani Planum, the landing site of Opportunity, scientists have succeeded.
Since its arrival on January 25, the Opportunity has spotted suggestive hints of past water —fine layers in bedrock that might be sedimentary rock deposited at the bottom of a lake or sea and an iron mineral that usually forms in the presence of water. In both cases, however, there are plausible alternative explanations. The layers could be volcanic ash or sediments carried by wind, or the iron could have formed directly from lava.
But close examination of the bedrock, exposed along the rim of the crater that the Opportunity has been scooting around in, provided four lines of evidence.
The most compelling is large quantities of jarosite, a mineral that contains iron, sulphur and trapped water. “This is a mineral that you’ve got to have water around to make it,” Squyres said.
Instruments measured high levels of sulphur in the rocks, probably in the form of sulphur salts. “The only way you can form such large concentrations of salt on Earth normally is to dissolve it in water and have the water evaporate,” a scientist said.
Photographs also show holes in the rocks roughly the shape and size of pennies. The scientists believe these are places where minerals carried by water formed crystals that subsequently dissolved or fell out.
The final evidence is found in the curious round pebbles, nicknamed blueberries, that are scattered around the surface and are also embedded in the bedrock. The blueberries, the scientists said, are objects known as concretions that form within sedimentary rocks.
The scientists do not yet know whether the rocks formed in water, but as to whether water later altered the minerals in the rocks, “the answer to that we believe, definitively, is yes”, Squyres said.
The discoveries make Meridiani Planum a promising candidate for a future robotic mission, at least a decade away, that would bring pieces of Mars back to Earth for closer examination.
Robert Zubrin, founder of the Mars Society, a space advocacy group, said the announcement had great scientific significance. “We’ve established that Mars is a place that could have supported life, if life can evolve from chemistry. If liquid water still exists underground, and there is ample evidence from more than this mission that it does, then astronauts could reach it and then culture it to see if there is any Mars life there.”
When people do go to Mars, he said, existing water would make greenhouse agriculture possible to sustain a base and also provide raw materials for fuel.
Louis Friedman, president of the Planetary Society, another advocacy group, said: “Mars never disappoints. The presence of water definitely correlates to the life question — whether it refers to life there on Mars or the ability to sustain life that we bring when going there.”