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This just in...

March 24, 2004

We just announced another big finding at Meridiani: We think that the rocks there were deposited in liquid water.

This finding is fundamentally different from what we announced three weeks ago. It's the difference between water you could draw from a well and water you could swim in. Last time, we had evidence that water had once seeped through the rock, changing its chemistry and its texture. This time, we think we see telltale signs suggesting that the rock was originally laid down in gently flowing liquid water.

This one didn't come easy. Several weeks ago, as we looked at the outcrop, we thought we were seeing what geologists call "cross bedding". Cross bedding means seeing layers in the rock that aren't parallel to one another, and cross bedding in a rock generally means that it was deposited in a flowing fluid. Either air (wind) or water (currents) can be the fluid. On earth, it turns out that there are some kinds of cross bedding that only form in liquid water... wind won't do it. We thought that that was what we were seeing in some of the Pancam images of the Meridiani outcrop. Maybe.

With even Pancam images not being sharp enough to resolve the problem, we turned to the only higher-resolution camera
we have: the Microscopic Imager. Back when we built the MI, we really only envisioned using it to image areas a few centimeters across. In fact, the field of view of the camera is only 3 cm wide. But here we had a problem where we needed ultra high-resolution images of rocks that were much, much bigger than an MI field of view. So we did something that we had really never envisioned doing...
we took some big image mosaics with the MI. There was one
rock called "Last Chance" that we took 152 images of! This
was a remarkable feat of robotic imaging, and Ken Herkenhoff, Eric Baumgartner, and a whole bunch of other people too numerous to name deserve enormous credit for pulling it off. (And hats off too to the good folks at ASI, who built us one heck of an arm.) Anyway, the whole thing paid off. The MI mosaics nailed the problem, showing us features in the rock that look like the distinctive signature of ripples formed in flowing water.

What are we going to do for our next trick? I have no idea. This whole thing has turned out to be such a surprise that I wouldn't dare guess what we're going to see next. The plan for Opportunity now is to crawl out of Eagle crater (which we've just done), and head 700 meters across the countryside to Endurance crater, which is much bigger and wilder-looking than Eagle. And then we'll see what we see.

Meanwhile, Spirit is way out ahead of Opportunity, distance-wise, working her way now along the rim of Bonneville crater. We haven't found any compelling evidence of water at Bonneville yet, but there's been some fantastic geology there... and the Columbia Hills beckon.