Lunar Boulder Tracks
What are they?
Boulder tracks occur when a boulder rolls on the surface of the Moon. The typical size of the boulder and track is about 7 meters (diameter) and 5
meters respectively. Boulders up to 23 meters and down to 1.3 meters have been identified. Boulder tracks are hypothesized to be the result of lunar
seismic activity or thermal cycling.
Why are these boulder tracks useful?
Because it is possible to deduce surface properties (bearing strength, density) without having to land a spacecraft there. This would enable
operational planning of landers and rovers.
Limitations of existing data
Although most of the present images showing boulder tracks exist in Lunar Orbiter photographs, less than 1% of the lunar surface was imaged at the
high resolution necessary to resolve these tracks. Typically, 1-5m resolution is needed to obtain useful data. High resolution coverage by the
upcoming Lunar Reconnaissance Orbiter will enable more tracks to be identified.
[Consolidated list of these tracks, with position on image and estimate of latitude/longitude, size estimates, other derived data.]
The list shown below is for the older Lunar Orbiter imagery. However, recent images from the Lunar Reconnaissance Orbiter have also shown boulder
tracks. Image nacl00000e09.tif (LRO image with boulder tracks) shows a large number of such tracks at a resolution of 1.62 m/pixel. A download of the
file will enable contrast enhancement to see >50 tracks near column 1370/row 17491 (image is 5064 by 52224).
It is desired to eventually replace the "Image Center" latitude and longitude with the track latitude and longitude. The supplementary data for the
lunar orbiter images provide the frame vertex coordinates, so with the track pixel position, this should be derivable.
No Lunar Orbiter sourcebook has been found correlating the framelet number with high resolution frame code number (i.e. H1, H2 or H3). This data can
only be obtained upon obtaining and viewing the high resolution frames.
The "Track Distance From Edge of Image" was originally referenced to 40 cm wide prints. The start point of the measurement is the edge of the Lunar
Orbiter film with the framelet numbers. It was never defined exactly where the start point is (i.e. the very edge of the film or the edge of the
visible image). Nevertheless, this data is very helpful in locating these "tiny" tracks in the large images.
Two sources of images have been useful for reviewing these tracks. These include the Lunar and Planetary Institute and the USGS Astrogeology Research
Program. When reviewing images for features such as tracks, realize that it is preferable to use film and that scans may not have the quality to see
some tracks, especially ones with short length.