Measuring track densities in lunar grains by image analysis

Details Measuring track densities in lunar grains by image analysis Measuring track densities in lunar grains by image analysis

Dec 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993asee....1q....b&link_type=abstract

In NASA. Johnson Space Center, National Aeronautics and Space Administration (NASA)/American Society for Engineering Education (

Computer Science

Backscattering, Computer Techniques, Cosmic Rays, Density Distribution, Energetic Particles, Image Analysis, Lunar Soil, Brightness, Gray Scale, Image Contrast, Noise Reduction, Pixels

Scientific paper

We have developed techniques to use digitized scanning electron micrographs and computer image analysis programs to measure track densities in lunar soil grains. Tracks were formed by highly ionizing solar energetic particles and cosmic rays during near surface exposure on the Moon. The track densities are related to the exposure conditions (depth and time). Distributions of the number of grains as a function of their track densities can reveal the modality of soil maturation. We used a sample that had already been etched in 6 N NaOH at 118 C for 15 h to reveal tracks. We determined that back-scattered electron images taken at 50 percent contrast and approximately 49.8 percent brightness produced suitable high contrast images for analysis. We ascertained gray-scale thresholds of interest: 0-230 for tracks, 231 for masked regions, and 232-255 for background. We found no need to set an upper size limit for distinguishing tracks. We did use lower limits to exclude noise: 16 pixels at 15000x, 4 pixels at 10000x, 2 pixels at 6800x, and 0 pixels at 4600x. We used computer counting and measurement of area to obtain track densities. We found an excellent correlation with manual measurements for track densities below 1x108 sq cm. For track densities between 1x108 sq cm to 1x109 sq cm, we found that a regression formula using the percentage area covered by tracks gave good agreement with manual measurements. Finally we used these new techniques to obtain a track density distribution that gave more detail and was more rapidly obtained than using manual techniques 15 years ago.

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