Automated searching of craters on Stardust interstellar foils

The NASA Stardust mission collected samples of particles in the tail of the Jupiter-family comet Wild 2, which have been returned to Earth and provided a glimpse into the nature of early Solar system. Samples of Wild 2 were collected during a flyby encounter between the orbits of Mars and Jupiter, and the Al foils lining the aerogel tiles of the Stardust interstellar tray represent approximately 13% of the total collecting area. The focus of this project is to develop a method to find a large number of these small craters (on the scale of hundreds of nanometers) on Stardust Al foils for the ultimate goal of studying the chemistry and structure of cometary material (elements such as Mg, Si, Fe, S, Ca, Al) with Auger spectroscopy and SEM-EDX. After we find a number of craters from the Stardust samples, an interesting subset of grains for FIB-TEM can be selected, with which we can determine the crystal structure and other important information. We implemented a MATLAB program, previously developed for the identification of crater-like features on other Stardust samples, to search for the grains on the Wild 2 samples and record the positions of the craters for future automated scanning of the samples. We are able to adjust the cross-correlation threshold (fitting score), library size of templates used to search the craters, and options to rescale the image to look for larger craters. Rough trials of the program show that it can search through hundreds of high-magnification SEM images within hours and detect more than 50% of the true craters