Carbonated Mars

Today folks using the Mars Reconnaissance Orbiter announced the discovery of a mineral called magnesium carbonate on Mars.


—Image courtesy NASA/JPL/JHUAPL/MSSS/Brown University

At first blush this seems like a pretty dry finding [pardon the pun]. What is a carbonate, and why should I care, you might ask.

When I tell you that it’s a mineral that requires liquid water to form, and its presence in bedrock almost certainly means early Mars had liquid water, you might reply, Yeah, and?

Even among scientists, it’s not gonna be news that Mars probably had bodies of water billions of years ago. What does make the finding cool is that carbonates dissolve readily in liquids with a low pH, aka, acids.

Deposits of carbonates dating back to early Mars therefore mean that water in at least some regions wouldn’t have been very acidic, and therefore could have given rise to life.

All this was revealed today during a briefing at the fall meeting of the American Geophysical Union, and I plan to have a proper news piece about it posted tomorrow. But even with the infinite space of the Web, there’s always some detail that has to be cut in news articles for the sake of getting to the point.

As luck would have it, I was seated next to a scientist who would relentlessly snicker every time a reporter asked a question about whether the new discovery would have any bearing on where to set down the Mars Science Laboratory.

It seemed like a legit question to me. The carbonates were found at Nili Fossae, a region of Mars that until recently had been one of the seven candidate sites for the roving lab.

Scientists had been working to rapidly hash out a final choice as the countdown to a planned 2009 launch loomed, and in late November Nili Fossae was among three of the seven to get the axe.

But then just a few weeks later NASA announced the MSL launch would be delayed by two years. So among the other details that might be rethunk, why not the landing site?

The snickering scientist later explained to me that his reason for mirth was that the lead study author giving the presentation was also part of the team of scientists that had been championing Nili Fossae for MSL.

“She did a pretty good job keeping a straight face,” he said.

The trouble is that all of the potential landing sites on Mars bear different kinds of minerals that need liquid water to form, so it will be a matter of debate whether carbonates make Nili Fossae suddenly more attractive than the four sites that did make the most recent cut.

And even with new science, there’s still the engineering side to consider.

Since the site is at a higher elevation on Mars, Nili Fossae affords less of a buffer between sky and ground. That means the craft would have less time to coast to a safe stop on its parachute, so all things being equal scientifically, the site got voted off the list.

I suppose time will tell whether any new science coming from the existing troop of Mars bots will impact the MSL’s future, including whether Nili Fossae earns itself a second chance.

Changing Planet