Studying Mars from millions of miles away

Terrestrial trucks with tough names and gritty commercials have nothing on a six-wheeled golf cart-sized vehicle. Operating millions of miles away on the unforgiving surface of Mars, the rover, Opportunity, landed in 2004 and was only expected to last for three months.

Eight years later, Opportunity is going strong, sending back useful information about the red planet. Using solar power, Opportunity outlasted its twin, Spirit, which stopped responding to Earth-bound signals about two years ago. The scientific vehicle recently provided even more evidence that Mars once not only had water, but that the water may have contained life.

Venturing near the Endeavour crater (named after the British ship that explorer James Cook led to New Zealand and Australia at around the same time as the American Revolution), Opportunity found rocks and minerals that provided more clues about the evolution and history of the surface of Mars.

“When we came onto the rim of the Endeavour crater, the fundamental geology completely changed,” explained Stony Brook University geochemistry professor Scott McLennan, who recently teamed up with scientists at several institutions to publish a paper in Science on their findings.

Looking at rocks that are likely older than 3.8 billion years old, McLennan and other scientists found extremely high zinc contents. Usually, zinc is at a level of 30 to 300 parts per million, but in these rocks, zinc was closer to 6,300 parts per million.

Zinc combines with sulfur and phosphorous. Scientists would expect to find these minerals, such as zinc sulfide or zinc phosphate, in rocks that had hydrothermal fluids that ran through them.

“People have known there was water on Mars for a long time,” McLennan explained. “The real issue was whether the water was in a liquid form at a time when you could have had environments in which life could have survived. We’re finding more geological environments in which water was active and conditions could have been habitable.”

Scientists also discovered gypsum near the crater. The chemical name for this mineral is calcium sulfate dihydrate. The last part of that name means the mineral has two water ions per molecule embedded in it.

“This was completely unexpected,” said McLennan.

Finding water tied up in the structure of minerals and rocks means they could become a resource for future exploration of Mars. For astronauts to make a round trip, they would need to make use of whatever water and fuel they could extract from Mars.

McLennan cautioned, however, that the volumes of water in the minerals on Mars are “not great.” Indeed, for every kilogram of gypsum, scientists could likely remove just over 200 grams (or 20 percent of the mineral’s weight) in water.

Much of McLennan’s research comes from analyzing the information sent back from Mars and simulating what he sees in his Stony Brook lab.

“What we were able to do,” said Joel Hurowitz, a research scientist at Jet Propulsion Laboratory who worked in McLennan’s lab to earn his doctorate, “was go into one lab and make rocks in a furnace and then take them to another lab and alter them in the presence of fluids that might have existed in the past on Mars. We could analyze the products of those water-rock reactions.”

Hurowitz described Stony Brook as a “spectacular place to grow up in as a student” and called McLennan a “leader” and “pioneer” in his area of research.

So, after all this extra time and information from Opportunity, where does Mars research go from here?

“Mars exploration is at a crossroads,” McLennan suggested. The first scientific priority over the coming decade is to begin the process of bringing samples back from Mars, so geologists like McLennan can study them.

President Obama, however, “cut planetary science and Mars exploration dramatically.”

The House and Congress have tried to reinstate some of the funding in those programs, but “who knows how it’ll end up,” McLennan added. He predicts the next year or so will determine whether scientists and politicians can make progress toward a return to Mars.

In the meantime, McLennan, who lives in Centerport with his wife Fiona, an assistant vice president of Human Resources at Columbia University, will continue to analyze information from the durable Opportunity rover.