This appears to relate to this morning's release of spectra, but was reported 2 days ago by a keen reporter!

" PASADENA, Calif., Jan. 30 — The Mars rover Opportunity may have detected the iron oxide — a possible sign of water from Mars' ancient past — that was the original motivation for sending it to a broad plain near the planet's equator, some scientists involved in the project said.

Scientists have been examining data from an instrument called the mini-thermal emission spectrometer, or mini-TES for short, that looks at infrared light radiated from the rocks and soil. The mix of infrared wavelengths identifies certain minerals.

Scientists did not confirm the hematite finding at a news conference this morning at NASA's Jet Propulsion Laboratory, which is managing the mission. Dr. Raymond E. Arvidson, chairman of the department of earth and planetary sciences at Washington University in St. Louis and deputy principal investigator for the mission, said the scientists were still completing calibrations and checks. "But if you look at any of the mini-TES members, they have huge smiles on their faces," he said.

On Earth, the iron oxide, known as gray hematite, usually forms in the presence of water, either hot springs or the bottom of a lake or sea, although it can also form out of oxygen-rich lava without water.

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As had been expected by the scientists, the dark pebbles and gravel on the surface appear to contain hematite, said Dr. Wendy M. Calvin, a professor of geology at the University of Nevada at Reno, as she reviewed mini-TES data with other team members early this morning.

But the fine reddish soil beneath the gravel did not show any signs of hematite, nor did the exposed bedrock, she said. This raises a new hematite question.

"This is what is in the back of my mind: Where did it come from?" Dr Calvin said.

In places where the rover had bounced on landing, the pebbles vanish, leaving sharp imprints of the air bags in the reddish soil. The hematite appeared to disappear, too, Dr. Calvin said.

"We don't see it in smushed areas," she said. "I don't know what happened to it."

If the gravel had just been pushed under the surface, as some of the scientists believe, then the hematite should still be evident, she said.

The alternate hypothesis is that the impacts pulverized the particles into tiny dust particles, too small to radiate the telltale hematite color signature.

When Opportunity rolls off the lander, it will stick instruments at the end of a mechanical arm into the soil, which should be better able to identify the minerals there.

Also curious, Dr. Calvin said, is that the exposed bedrock did not give off any telltale color signatures: no sandstone, no silicates, no carbonates — minerals that would be seen in sedimentary rocks on Earth. It is possible that a thin layer of dust on the rocks is obscuring the readings."