The Mars rover Opportunity has explored Victoria crater, a ~750-meter eroded impact crater formed in sulfate-rich sedimentary rocks. Impact-related stratigraphy is preserved in the crater walls, and meteoritic debris is present near the crater rim. The size of hematite-rich concretions decreases up-section, documenting variation in the intensity of groundwater processes. Layering in the crater walls preserves evidence of ancient wind-blown dunes. Compositional variations with depth mimic those ~6 kilometers to the north and demonstrate that water-induced alteration at Meridiani Planum was regional in scope.

Such a report on Earth would be fairly run of the mill, but on Mars, every study of every geological field site moves us palpably closer to understanding the past, and seemingly dynamic, geological processes on the planet most likely to have ever harbored live in our solar system, other than our own.

This report is published in today’s issue of Science. It is based mainly on dta acquired by the robot Opportunity during a traverse along the northern rim of the crater during which time the rover photographed cliff faces. Here’s a map of the rover’s path:

From Figure 1 of the cited paper. Opportunity’s traverse at Victoria crater. Image acquired by the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment camera. [image is rotated 90 degrees to fit on blog]

The paper is detailed and interesting, but not OpenAccess. But, it is fairly technical and a very good press release is available here. Here are the important findings, paraphrased from the release:

• The paper is a broad summary of observations that were released incrementally as they were made over the last two years.
• Obervations of hematite spheres (known as blueberries), sulfate-rich sandstone and small chunks of rock containing kamacite, troilite and other minerals commonly found in meteorites — are consistent with Opportunity’s findings across Meridiani Planum, the rocky plateau the size of Oklahoma where the rover landed Jan. 24, 2004.
• The observations here show that the processes observed earlier at Endurance Crater in 2004 are consistant across a regional scale.
• But there are differences:
• The rim of Victoria Crater is about 30 meters (32.8 yards) higher than the rim of Endurance
• As the rover drove south to the second crater, the hematite blueberries in the soil became ever fewer and smaller, even though rocks deep inside the crater contain big blueberries. This indicates that the rocks higher up had less interaction with water, etlling us that the water’s source was likely underground.

Squyres, S., Knoll, A., Arvidson, R., Ashley, J., Bell, J., Calvin, W., Christensen, P., Clark, B., Cohen, B., de Souza, P., Edgar, L., Farrand, W., Fleischer, I., Gellert, R., Golombek, M., Grant, J., Grotzinger, J., Hayes, A., Herkenhoff, K., Johnson, J., Jolliff, B., Klingelhofer, G., Knudson, A., Li, R., McCoy, T., McLennan, S., Ming, D., Mittlefehldt, D., Morris, R., Rice, J., Schroder, C., Sullivan, R., Yen, A., & Yingst, R. (2009). Exploration of Victoria Crater by the Mars Rover Opportunity Science, 324 (5930), 1058-1061 DOI: 10.1126/science.1170355

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