NASA's Mars Curiosity rover drilled into a rock and found that it contained a clay-like material. That's the news. The implication is much larger: Mars may once have had an environment hospitable to life.

One of the tricky aspects of science is that its revelations tend to be more exciting the more attention you pay to science. For those who are generally disinterested in science, there's a high bar for an exciting announcement; for scientists, a graph showing just the right data point can be validation of a life of effort. The job of organizations like NASA is bridging the two groups, presenting the small, important discoveries of its scientists into something that thrills the world.

The small important discovery announced today is that the Mars rover, Curiosity, analyzed the component elements of dust from a rock that lies in what may once have been a stream bed. It found a variety of common elements you'd find on Earth — oxygen, hydrogen, sulfur, etc. — what NASA calls "some of the key chemical ingredients for life." NASA's press release quotes the project's lead scientist: "A fundamental question for this mission is whether Mars could have supported a habitable environment. From what we know now, the answer is yes." It doesn't currently, mind you. But it could have. "This ancient wet environment, unlike some others on Mars," NASA notes, "was not harshly oxidizing, acidic or extremely salty."

At right, the hole drilled by Curiosity. At left, an earlier, less indicative experiment.

That's fine. But more evocative is the more detailed description of what was found.

"Clay minerals make up at least 20 percent of the composition of this sample," said David Blake, principal investigator for the CheMin instrument at NASA's Ames Research Center in Moffett Field, Calif.

These clay minerals are a product of the reaction of relatively fresh water with igneous minerals, such as olivine, also present in the sediment. The reaction could have taken place within the sedimentary deposit, during transport of the sediment, or in the source region of the sediment.

There's something striking about that: the idea that clay-like material was created near a stream on Mars some indescribably long time ago and has been sitting there since. Perhaps even while life was forming on Earth, this rock came into being on Mars. The scientists clarified that they can't be sure how the timelines of habitability line up, though it was probably about 3 billion years ago — which, give or take millions of years, could line up with the first records of life on Earth.

John Grotzinger, Curiosity project scientist, summarized the findings in response to a question from the press. "We have found," he said, "a habitable environment that is so benign and supportive of life, that probably if this water were flowing and you were around, you would have been able to drink it."

Drilling a rock is not exciting. Speculating about visiting the surface of another planet, drinking from a flowing stream? The mind reels.