|A view from the Mars rover Opportunity. The rover sampled a rock containing abundances of elements like aluminum, calcium and magnesium, which adds to a portrait of a planet that was once a water-rich world with conditions amenable for life.|
The discovery of what appears to be a clay-rich rock on Mars adds to the portrait of the planet as one that once — in its youth, more than three and a half billion years ago — was a water-rich world with conditions amenable for life, NASA scientists said Friday.
The rock in question, about the size of a person’s forearm, was examined by the Mars rover Opportunity, the older of the spacecraft still in operation on the planet. The newer rover, the Curosity, landed last August and has been hogging the headlines ever since; in a news conference on Friday, NASA officials proudly called attention to the fact that the Opportunity, launched nearly a decade ago, was still soldiering on with valuable field work.
The newly discovered rock, which scientists named Esperance, is one of the oldest rocks that the Opportunity has looked at during its nine and a half years on Mars. From the abundances of elements like aluminum, calcium and magnesium, the mission’s scientists concluded that the rock is very rich in clay minerals, which could have formed from copious water running over volcanic rocks.
“This is powerful evidence that water interacted with this rock and changed its chemistry, changed its mineralogy in a dramatic way,” said Steven W. Squyres, the principal investigator.
The Opportunity and a twin rover, the Spirit, landed on Mars in January 2004, intended for a three-month mission. The Spirit got stuck in 2009 and has not been heard from since 2010, but the Opportunity remains in “remarkably good health,” said John Callas, the project manager.
“It is now Sol 3,331 in our 90-day rover mission,” Dr. Callas said. A sol is a Martian day, which is 39 minutes longer than a day on Earth.
The Opportunity has already found many signs of flowing water in Mars’s ancient past, but of very acidic water. “In fact, what Opportunity has mostly discovered evidence for in the past was sulfuric acid on Mars,” Dr. Squyres said.
The clays in Esperance — which means “hope,” but the rock was actually named after a gold mine in French Guiana where a project member had done research — formed in more neutral waters. “This is water you could drink,” Dr. Squyres said. “This is water that was probably much more favorable in its chemistry, in its pH, in its level of acidity, for things like prebiotic chemistry, the kind of chemistry that could lead to the origin of life.”
Last December, Dr. Squyres talked about a light-colored fine-grained rock in the same area, which appeared to possess a thin crust of clays, but otherwise had a composition typical of most Martian rocks.
Esperance contains a much higher concentration of clays, he said.
With its limited instruments, the Opportunity cannot look for carbon-based molecules that could be the building blocks of life. The Curiosity, which landed on another part of Mars, is larger and has a more advanced chemistry laboratory, and Dr. Squyres was asked if he wished that the Opportunity had the same capabilities.
“Absolutely,” he said with a chuckle. “No question about it. This is a treasure trove.”
Opportunity is now headed for a 180-foot hill called Solander Point, less than a mile away. The slope will allow the rover to tilt its fixed solar panels northward to the Sun as winter approaches. Outcrops at Solander Point could reveal more clay-rich rocks.
Meanwhile, elsewhere on Mars, the Curiosity is about to wrap up its work on a couple of intriguing rocks that have painted a similar story of the planet’s early history. It will then head toward its primary goal, an 18,000-foot mountain where rocks near the base are believed to contain clay minerals. That five-mile trip is expected to take about a year.