Image #2 Grinding Wheel Profile

This graphic dubbed by engineers as the "Grinding Wheel Profile" is 
the detective's tool used by the Opportunity team to help them 
understand one of the processes that formed the interior of 
McKittrick rock.  Scientists are looking for clues as to how layers, 
grains and minerals helped create this rock, and the engineers who 
built the rock abrasion tool (RAT) wanted to ensure that their 
instrument's handiwork did not get confused with natural processes.

In the original microscopic image underneath the graphics, engineers 
and scientists noticed "layers" or "scratches" on the spherical 
object nicknamed "blueberry" in the lower right part of the image. 
The designers of the rock abrasion tool noticed that the arc length 
and width of the scratches were similar to the shape and size of the 
rock abrasion tool's grinding wheel, which is made out of a pad of 
diamond teeth.

The scrapes on the bottom right blueberry appear to be caused by the 
fact that the berry got dislodged slightly and its surface was 
scraped with the grinding pad.  In this image, the large yellow 
circle is the overall diameter of the grinded hole and the largest 
yellow rectangular shape is the area of the grinding wheel bit. The 
smaller yellow semi-circle is the path in which the center of the 
grinding tool follows, indicated by the orange arrow arcing around 
the solid yellow circle (center of grinding tool).  The grinding tool 
spins about itself around its own center at 3,000 rpm (revolutions 
per minute) while it simultaneously spins in an orbit around the 
center of the rock, indicated by the larger orange arrow to the left.

The grinding tool is 22 millimeters (0.9 inches) in length and the 
actual grinding surface, which consists of the diamond pad, is 1.5 
millimeters (0.06 inches) in length, indicated by the two smaller 
rectangles.  You can see that the smaller bottom rectangle fits 
exactly the width of the scrape marks.

The grooves on the blueberry are also the same as the curvature of 
the arced pathway in which the grinding tool spins.

By overlaying appropriately scaled representations of the rock 
abrasion tool schematics, the evidence reveals a strong indication 
that the scrapes on the blueberry were "RAT" induced rather than 
caused by some natural, geologic process.

The rock abrasion tools on both Mars Exploration Rovers were supplied 
by Honeybee Robotics, New York, N.Y.

Image Credit:  NASA/JPL/Cornell/US Geological Survey

APPROVED BY:  Larry Soderblom, SOWG chair, and Phil Chu, RAT team, 
607/227-8023 cell

CAPTION WRITER:  Christine Johnson 818/667-7853 cell

RELEASE DATE:  February 25, 2004

IMAGE FILE NAME: xpe_MI_RAT_GW_PROFILE.jpg

SOURCE FILE NAME(S): 1M130859270EFF0454P2959M2M1.jpg

SUMMARY INFORMATION:  Graphic Profile of RAT over Microscopic Image 
of First Rat Hole on Opportunity

NAME OF SUBMITTER:  Phil Chu

INSTITUTION:  Honeybee Robotics

THEME/TEAM/GROUP:  RAT

SOL OF OBSERVATION:  30

EARTH DATE OF OBSERVATION:  February 23, 2004

TITLE OF IMAGE: Grinding Wheel Profile

CAPTION:  Above