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Analysis of an Impact Micro Crater

NASA's Stardust was a famous mission to return comet dust samples to Earth for investigation. These samples were collected by the Stardust spacecraft first launched in 1999 and returning the samples collected from encounters with the comets Annefrank (2002) and Wild 2 (2004) in 2006. The prime intention was to collect particles in a special capture medium unharmed. Nevertheless, some dust particles particles impacted on parts of the spacecraft. To obtain a better understanding of the microscopic impact craters produced during the mission, an experiment was carried out to simulate these on Earth. The analysis of one of these artificial craters produced on a piece of aluminum foil with the XFlash® FLatQUAD is subject of this application example. (Sample courtesy: A. Kearsley, Natural History Museum, London, UK)

 

The first image shows an overlay of the backscattered electron image and an EDS map of Mg, S, and Ca of a crater, obtained with a conventional large area SDD on a 35° SEM chamber port. Only part of the impacted particle residue is visible to the EDS detector due to shadowing effects. Measurement conditions were 20 kV acceleration voltage, 3 nA beam current and 15 h 54 min acquisition time, to obtain a 1024 x 768 pixel map with 380 nm pixel size.

The next image shows a map of the same crater obtained with the XFlash® FlatQUAD. It shows no shadowing, the complete particle residue is mapped. Measurement conditions were 6 kV acceleration voltage, 3 h 55 min acquisition time at 175 kcps ICR, resulting in a 800 x 600 pixel map with 380 nm pixel size.