Kaibab: The plot thickens . . . but what's it made of?
View a larger image (200 kB) or learn about other sol 13 images.
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.
"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
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!