rock's name was inspired by Humphries Peak - the tallest peak in
Arizona and part of the San Francisco volcanic complex. Standing
approximately .6 meters (about 2 feet) tall, "Humphrey" is one of
the largest blocks of what scientists believe is ejected material
from one of the rover's long-term targets, the crater dubbed
"Bonneville." Likely a basaltic rock, the fractures in "Humphrey"
are thought to have been caused by the impact as it was hurled from
the crater to its current resting place. Scientists are eager to
investigate ejecta rocks, as they give a glimpse of the composition
of what lies beneath the martian surface. The engineering and
science teams are preparing to brush and then grind "Humphrey" with
Spirit's rock abrasion tool. The hope is to remove as much dust as
possible so they can examine the coating and then the exposed
undersurface after grinding with the cameras and the miniature
thermal emission spectrometer.