Spirit Says Goodbye to 'Home Plate'
For the past several weeks, Spirit has been examining spectacular layered
rocks exposed at "Home Plate." The rover has been driving around the
northern and eastern edges of Home Plate, on the way to "McCool Hill."
Before departing, Spirit took this image showing some of the most complex
layering patterns seen so far at this location.
The layered nature of these rocks presents new questions for the rover
team. In addition to their chemical properties, which scientists can study
using Spirit's spectrometers, these rocks record a detailed history of the
physical properties that formed them. In the center of this image, one
group of layers slopes downward to the right. The layers above and below
this group are more nearly horizontal. Where layers of different
orientations intersect, other layers are truncated. This indicates that
there were complex patterns of alternating erosion and deposition
occurring when these layers were being deposited. Similar patterns can be
found in some sedimentary rocks on Earth. Physical relationships among the
various layers exposed at Home Plate are crucial evidence in understanding
how these Martian rocks formed. Scientists suspect that the rocks at Home
Plate were formed in the aftermath of a volcanic explosion or impact
event, and they are investigating the possibility that wind may also have
played a role in redistributing materials after such an event.
Images like this one from panoramic camera (Pancam), which shows
larger-scale layering, as well as those from the microscopic imager, which
reveal the individual sand-sized grains that make up these rocks, are
essential to understanding the geologic history of Home Plate.
This view is an approximately true-color rendering that combines separate
images taken through the Pancam's 753-nanometer, 535-namometer, and
432-nanometer filters during Spirit's 774th Martian day (March 8, 2006).
Image Credit: NASA/JPL-Caltech/Cornell
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