The Stardust Interstellar Dust Collector Crater Origins and Hypervelocity Cratering at Oblique Angles in Aluminum Foil

From 1999 to 2006 the NASA Stardust mission collected cometary particles from the Wild 2 comet and interstellar dust from the interstellar medium in two collectors made from aerogel tiles and aluminum foil. By studying their isotopic compositions, these particles can provide us with information about nucleosynthetic processes in stars. Both collector trays are being studied for traces of these particles, though a number of challenges have arisen in doing so. Identifying impact craters in the aluminum foil on the interstellar collector tray has been incredibly difficult. In addition to being only a few micrometers or less in diameter, many craters may have been caused by debris from the spacecraft instead. It is currently impossible to tell a crater’s origin without much more detailed analysis. One way to determine a crater’s origin is by examining the direction of impact. Interstellar dust is likely to have impacted the collector tray normal to its surface, while other debris impacted at a variety of angles. However, this directional information is not obvious in the craters on the aluminum foil strips. We examined the results of two hypervelocity test shots of particles into aluminum foil targets, varying the angle of impact and the particle sizes used. Auger elemental analysis was carried out on a number of craters across each foil. Many craters at higher impact angles (>60°) display the presence of deposited material around a crater, creating a spray pattern in the direction aligned with the direction of impact. No such patterns are observed for impacts closer to normal angles. When applied to the Stardust interstellar collector, such information may help in distinguishing craters caused by debris from those caused by interstellar dust, without the use of extensive analysis first.