Kaibab: The plot thickens . . . but what's it made of?

Arizona State University geological scientist Jack Farmer is serious about geology, and leaves no stone un-turned when investigating the FIDO test site. His team spent today investigating the Kaibab-site Pancam data and made some interesting discoveries.

One of the images they worked with was this one which shows a close-up of cross-bedding at Kaibab that scientists on the MER team think formed by water (see sol 11). While Pancam data confirmed the presence of coarse particles and therefore the hypothesis that it was formed by water, it did not give information about the mineralogy of the rock.

Jack Farmer

"What we had hoped to accomplish next was to get a close-up look at the rock with the Microscopic Imager and some element and mineral analysis with the APXS and Mössbauer spectrometers," said Farmer. "The Pancam data we had was pretty convincing that Kaibab's formation was fluvial (water based). Now we wanted to know whether it was a river system or a marine system that was at work."

If the analysis taken by APXS and Mössbauer showed that the rock contained a lot of coarse-grained, poorly sorted fragments of feldspar, quartz and clays, it would provide support for the hypothesis that the sediments deposited at Kaibab were derived from an uplifted area where granite had been exposed by rivers.

Granite is a type of rock that forms on continents when magma (molten rock) crystallizes deep below the surface. The granite is exposed if earthquakes uplift it along faults and flowing water or wind then tears it down by carrying the materials away. Examples include the Sierra Nevada Mts. of California, the White Mts. of New Hampshire and Pike's Peak in the Colorado Rockies.

If the element-analysis of Kaibab revealed that the rock contained primarily fine-grained quartz, then it would be concluded that Kaibab was most likely wind blown sand at one time, and existed as something like a dune-field near the ocean.

"What actually happened is that we were unable to deploy the arm instruments (Microscopic Imager, APXS and Mössbauer Spectrometer) because we were closer to the rock-face than we thought," explains Farmer. (see rover status story) "This meant having to decide whether to stay at the site another two sols to re-deploy the arm, or to move on."

Since scientists had also requested tests from the Mini-TES (Mini-Thermal Electronic Spectrometer) instrument, which sees infrared radiation emitted by objects, they had data that confirmed the presence of feldspar, quartz and clays. "The Mini-TES results, along with the coarse-grained nature of the cross-bedded materials seen in Pancam images (see previous story) was enough to convince us that Kaibab was derived from an uplifted area where granite had been exposed by rivers, and we were ready to move on," confirmed Farmer.

On that basis it was onward to Bonneville!