Engineering topics

R. Harrington

Publications and source records attributed to R. Harrington.

3 records

NASA NTRSDate not supplied

Sample Polishing Without Epoxy

In recent years, we have received requests for meteorite sample sections to be prepared without using epoxy impregnation or mounting. The reasoning for these requests ranges from potential contamination of analyses from epoxy chemical components to degradation of instrumental vacuum from epoxy outgassing (e.g., SEM, SIMS, EPMA, etc.). An alternative approach that we employ involves sawing off a 1-5 mm thick wafer of the sample. The wafer is ground using silica carbide lapping media wetted with 190 proof ethyl alcohol to make both sides flat and parallel. The sample is then polished on one or both sides using diamond paste or dry diamond powder on a rotating lap wheel until the desired finish is obtained. The sample is cleaned in between steps using 200 proof ethyl alcohol in an ultrasonic cleaner. Friable and altered samples need to have higher thickness in order for polishing to be attempted. Without epoxy to hold the sample together or a glass slide for backing, the sample needs additional material to provide the necessary support structure. The machining steps of this process need to be undertaken at a much slower speed than in traditional thin or thick section preparation.

Meteorite↗

NASA NTRSDate not supplied

Requesting Antarctic Meteorite Samples for Research

The U.S. Antarctic meteorite program began in the 1970’s and has provided more than 24,000 samples. The program is based on a three agency agreement between NASA, the National Science Foundation, and the Smithsonian Institution. The collection, stored at the Johnson Space Center and the Smithsonian, is one of the largest collections of meteorites in the world and features samples from the moon, Mars, asteroids, and material from the early solar system. A brief overview of the collection shows it contains 92.2% ordinary chondrites (7205 H, 9126 L, 3890 LL, 146 enstatite, 30 R chondrites, 3.2% (973) carbonaceous chondrites, 3.7% (560) achondrites (1.7% HED), 118 irons, 27 pallasites, 41 mesosiderites, as well as many puzzling, ungrouped meteorites. JSC has sent splits of over 20,000 meteorite samples to more than 500 scientists around the world since 1977. After the meteorites are collected in Antarctica, they are shipped frozen to JSC in Houston, TX, arriving in April following the field season. The Astromaterials Curation Office at JSC is responsible for: - providing supplies and tools for the field team. - receiving the frozen meteorites. - staging: repackaging and changing the samples’ field identification numbers with official names. - submitting the names to the Nomenclature Committee of the Meteoritical Society for approval as new meteorites. - providing storage and handling of the meteorites in a class 10,000 clean room. - initial processing: weighing, measuring, describing, and photographing the sample and providing a chip for classification to the Smithsonian Institution staff. - the issuing of two newsletters per year, announcing hundreds of new meteorites. - the handling of requests from the scientific community and the allocation of those requests that are approved. - making petrographic thin and thick sections for the JSC library and scientific investigators. - maintaining the meteorite database with more than 76,000 sample splits.

C.E. Satterwhite↗

NASA NTRSDate not supplied

The Dominion Range (DOM) Lunar Regolith Breccia Pairing Group

With the Chang-E missions, ANGSA sample analysis, and Artemis mission progress as three examples of excitement about lunar science, we want to reaffirm and emphasize the importance of lunar meteorites to our understanding of the Moon. There are over 600 lunar meteorites documented with a total combined mass over 1000 kg, roughly 3x more mass than the Apollo samples. The 2018-19 season ANSMET team recovered lunar meteorites, reported in three different newsletters. Because these have been announced across three years, 2019-2022, we here provide an overview of their characteristics, reported findings, and comparison to other lunar meteorites. In particular, we emphasize their unique properties and how they may contribute to advancing lunar science. Eight pieces were recovered in the 2018-19 ANSMET season. All were found near the northern edge of the blue ice tongue or at the edge in the moraine. The largest mass is 45.87 g, ranging down to lowest mass of 5.46 g.

meteorite↗