Aerogel keystones: Extraction of complete hypervelocity impact events from aerogel collectors

Abstract

Abstract-In January 2006, the Stardust mission will return the first samples from a solid solar system body beyond the Moon and the first samples of contemporary interstellar dust ever collected. Although sophisticated laboratory instruments exist for the analysis of Stardust samples, techniques for the recovery of particles and particle residues from aerogel collectors remain primitive. Here, we describe our recent progress in developing techniques for extracting small volumes of aerogel, which we have called "keystones," which completely contain particle impacts but minimize the damage to the surrounding aerogel collector. These keystones can be fixed to custom-designed micromachined silicon fixtures (so called "microforklifts"). In this configuration, the samples are self-supporting, which can be advantageous in situations where interference from a supporting substrate is undesirable. The keystones may also be extracted and placed onto a substrate without a fixture. We have also demonstrated the capability of homologously crushing these unmounted keystones for analysis techniques that demand flat samples.

Investigation of ion beam techniques for the analysis and exposure of particles encapsulated by silica aerogel: Applicability for Stardust

“…Therefore, these may not be representative of the features preserved in the Stardust collectors where the encounter velocity was approximately 6 km/s. The LEO-derived impact events tend to show a high degree of particle fragmentation on the micron and sub-micron scales (e.g., Hörz et al 2000;Westphal et al 2004). Therefore, it is reasonable to assume that if cometary particles are similar to fluffy anhydrous IDPs, they may exhibit similar behavior upon collision with the silica aerogel collectors, even at the lower velocity.…”

“…The development of the extraction technique described in Westphal et al (2002Westphal et al ( , 2004) is a significant milestone. However, it is only the first stage of the analytical strategy for Stardust particles.…”

“…This allows the nuclear microprobe's ability to detect both inorganic and organic material in a wide range of particles to be tested. After implantation, a small wedge or the so-called "keystone" of aerogel containing the analogue particles was extracted from the bulk using the mechanical recovery techniques described in Westphal et al (2004).…”

“…Laser ablation extraction has also been used to recover particles accelerated into silica aerogel using a light-gas-gun . Westphal et al (2002), using automated micromanipulators and glass micro-needles, extracted individual particles down to 3 µm in diameter and, more recently, keystones of silica aerogel containing entire impact tracks (Westphal et al 2004). Beyond mechanical extractions, it is important to investigate emerging technologies that could be suitable for Stardust.…”

“…These particles will be the first sample return from a solid planetary body since the Apollo missions. In preparation for the return, analogue particles were implanted into a keystone of silica aerogel that had been extracted from bulk silica aerogel using the optical technique described in Westphal et al (2004). These particles were subsequently analyzed using analytical techniques associated with the use of a nuclear microprobe.…”