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Astromaterials Newsletter – Volume 1 No. 1 March 2019

Cosmic Dust News

Marc Fries, Cosmic Dust Curator

The Cosmic Dust (CD) collection is in the midst of a period of significant changes that range from sample allocation practices to collection and processing procedures. The highlights are described here, and persons interested in details are invited to contact Dr. Marc Fries, the Cosmic Dust Curator.
Changes to Loan Procedures
When Cosmic Dust started lending material almost forty years ago, analytical instrumentation was significantly less capable than that used today, and so the typical measurement would consume an entire CD particle. As a result, material was loaned with no expectation that it would be returned to the CD collection. Since then, advances in instrumentation and sample processing routinely allow multiple measurements on a single particle.
Ultramicrotomy and focused ion beam (FIB) make sub-sectioning of CD material commonplace, allowing multiple sub-samples and many analyses per particle. This allows samples to be shared or re-issued for analyses between laboratories. CD policies have been updated to follow precedent and standards established throughout NASA's collections. Requests for CD material now typically cover a period of five years and require an official loan agreement approved by the requesting institution and by NASA.
If needed, a request for a loan extension can be made to the Cosmic Dust Curator. Loaned CD material is subject to return to the CD collection after the loan period is complete. Material is subject to recall if requested by a different investigator, but in that case, completion of work under the initial request will be prioritized. These changes bring the CD collection to the same standards as other NASA small particle collections, including Stardust and NASA's portion of Hayabusa samples.
Perseid Timed Collection
A "timed collection" was performed shortly after the peak activity of the Perseid meteor shower in an attempt to collect material from that shower. The Perseids are debris from comet 109P/Swift-Tuttle, a potentially hazardous object (PHO) that has never been visited by spacecraft. Two small-area collectors were exposed for four hours on 20 Aug 2018. The collectors have been imaged and preliminary PSD analysis performed (Figure 1). Sixty-four particles have been removed to date of which 11 are preliminarily classified as cosmic or possibly cosmic.
These particles will be made available for allocation following a moratorium of 8 weeks as outlined in JSC Policy memo #42. After the moratorium, requests for the new materials may be submitted as per the usual process at https://curator.jsc.nasa.gov/dust/samreq.cfm. As described in policy memo #42, The hiatus is intended to allow sufficient time for the scientific community to self-organize into consortia to study these samples. This practice is designed to favor the scientific quality of a request rather than the speed with which it is submitted. Requests will be accumulated by the Curator until the end of the hiatus and reviewed all at once. Formation of consortia to study these materials is encouraged but not required.
Figure 1: Example of a possibly cosmic particle from the 2018 Perseid Timed Collection
Figure 1: Example of a possibly cosmic particle
from the 2018 Perseid Timed Collection
"Dry" Collected Particles
Silicone oil is used for CD collection, and while it is an efficient capture medium, it is also a contaminant for various types of studies. CD has previously flown foam collectors in place of oil-coated ones as an investigation into providing "dry", or oil-free, particles. Removing material from foam is a challenge, and as part of this effort, Dr. Christopher Snead has been investigating methods for reliable removal of particles. Particles will be removed from dry collector W7312, which was flown in 2014. Extracted material will be mounted as a test of removal techniques, and as a preliminary examination of the longevity of foam-collected particles.
These particles will be made available for request, ahead of additional "dry" collection flights planned for the near future. As special particles with an expected high level of interest from the community, requests for them will be treated the same as the Perseid timed collection particles with a hiatus of 8 weeks before proposals are considered. Furthermore, the dry-collected particles will be announced in a subsequent issue of the Astromaterials Newsletter once they are available.
New Catalog Released
Catalog number 22,1 has been released and the material therein is available for request. U2168 flown during August-October 2016, and W7317-19 flown between May and August 2017. The new catalog can be accessed from the NASA Cosmic Dust catalog page at https://curator.jsc.nasa.gov/dust/catalogs/index.cfm.
Balloon-Based Collection
CD has historically collected particles using high-flying aircraft. We are investigating adding balloon-based collection to supplement collection by aircraft in order to facilitate dry particle collection, improve collection flexibility, and to build programmatic depth. Students at Texas A&M are currently building a prototype CD collector for NASA high-altitude balloons, known as CARDINAL (Cometary and Asteroidal Research of Dust in Near-space Atmospheric Levels).
CARDINAL is a solar-powered collector suitable for very long duration flights that uses a pair of collectors on a rotating arm. The collectors are stored during launch and landing, and the low airspeed over them may be especially suitable for dry sample collection. Timed collection should be easier and more efficiently performed on a long-duration platform, as well. CARDINAL will be complete by the end of the academic year and two test flights on NASA high altitude balloons will occur in June 2019 and then later this year.
Imaging of Collectors
CD is exploring the addition of a new standard procedure to image entire collectors before particles are extracted. This is done for two reasons: good general curation practice, and to assist in identifying material from specific parent bodies through timed collections. Particle size distribution (PSD) analysis should indicate when a deviation from the sporadic background has occurred, but addition of spectroscopic means to identify cosmic and potentially cosmic material in situ may be required to complete the analysis. Progress and results will be presented in future communications.
Study of "Old" Collector Oil
CD material is collected by high-altitude aircraft using silicone oil coated on flat-plate collectors, and CD recently investigated the properties of one of the oldest collectors to test whether the oil degrades with time. Small-area collector W7016, which was flown in 1981, was drawn from curation storage for processing. One dozen particles were removed from W7016 and processed via the standard method, to include SEM/EDS analysis. Kathleen McBride reports that the mechanical behavior of the silicone was indistinguishable from more recent collectors and reports no problems in removing and handling the samples. Knowing that the oil does not appreciably degrade over the current lifetime of the collection ensures that particles from all collectors in the Catalog are available for request.