From the Editor Nanoanalysis of Presolar Grains

When I see a polished section of an iron meteorite in a museum, I think how amazing it is that this piece of solar system debris survived its descent through the Earth’s atmosphere to provide us with physical evidence of solar system formation. T ese meteorites, from the metallic core of a planet or asteroid that broke into fragments, contain phases originally analyzed for elemental composition decades ago using X-ray spectrometry in the electron probe microanalyzer (EPMA). As traditionally operated, the EPMA has a spatial resolution of analysis about 1 µm. However, recent research on certain types of meteorites requires much better spatial resolution. T ere are three main types of meteorites: iron meteorites, stony meteorites, and stony-iron meteorites. Some stony meteorites, known as chondrites, are aggregates of early solar system components and occasionally contain small inclusions believed to have originated in debris that predates our solar system. T ese sub-µm-sized presolar grains have unusual isotope signatures in various elements, and some may contain nanometer-sized diamonds. T ese meteorites require “nanoanalysis,” elemental analysis with a spatial resolution on the order of a few nanometers, about a hundred times better than that possible with the EPMA. One method of achieving nanoanalysis is to produce an electron-transparent thin specimen of the meteorite and analyze it using X-ray spectrometry in a scanning transmission electron microscope (STEM-EDX); in this case the analytical spatial resolution can be 1–5 nm. Another method is to analyze a polished bulk specimen with Auger electron spectrometry (AES), where the primary electron beam can be focused to 5–10 nm and Auger electrons escape from within 3 nm of the surface, yielding an analytical resolution of about 10 nm. A third method known as atom probe tomography (APT) uses position-sensitive time-of-fl ight mass spectrometry to locate atoms in three dimensions with near-atomic resolution (<1 nm).

Finding presolar grains in a chondrite requires mass spectrometry: nano-scale secondary ion mass spectrometry (NanoSIMS) can identify grains with presolar isotope ratios for later AES analysis (see article in this issue by Floss), and APT can fi nd grains with presolar isotope ratios as well as determine the compositions of phases within these grains (article by Lewis et al.). Finally, many site-specifi c analyses require specimen preparation to be done with a focused ion beam (FIB) milling instrument. A new mounting method simplifi es specimen preparation for APT. T is method has been applied to atomic-level analysis of an iron-nickel meteorite (article by Rout et al.).

Charles Lyman Editor-in-Chief

Publication Objective: to provide information of interest to microscopists.

Microscopy Today is a controlled-circulation trade magazine owned by the Microscopy Society of America that is published six times a year in the odd months. Editorial coverage spans all microscopy techniques including light microscopy, scanning probe microscopy, electron microscopy, ion-beam techniques, and the wide range of microanalytical methods. Readers and authors come from both the life sciences and the physical sciences. The typical length of an article is about 2,000 words plus fi gures and tables; feature articles are longer. Interested authors should consult “Instructions for Contributors” on the Microscopy Today website:

ISSN 1551-9295

Disclaimer The Microscopy Society of America and the editors cannot be held responsible for opinions, errors, or for any consequences arising from the use of information contained in Microscopy Today. The appearance of advertising in Microscopy Today does not constitute an endorsement or approval by the Microscopy Society of America of any claims or information found in the advertisements. By submitting a manuscript to Microscopy Today, the author warrants that the article is original or that the author has written permission to use copyrighted material published elsewhere. While the contents of this magazine are believed to be accurate at press time, neither the Microscopy Society of America, the editors, nor the authors can accept legal responsibility for errors or omissions.

© Copyright 2015 by the Microscopy Society of America. All rights reserved.

Editorial Staff

Charles E. Lyman, Editor-in-Chief (610) 758-4249

Gennifer Levey, Production Manager (212) 780-0315

Ron Anderson, Executive Editor Phil Oshel, Technical Editor Robert Price, Associate Editor Stephen Carmichael, Columnist Eric Clark, Pioneers Editor Richard Edelmann, Education Editor Deb Kelly, Microscopy 101 Editor Thomas E. Phillips, Consulting Editor Paul Webster, Calendar Editor John Shields, Humor Editor Nikolaus Cordes, Digital Content Editor Thomas Kelly, Chief Awards Judge T

Advertising Sales M.J. Mrvica Associates, Inc. 2 West Taunton Avenue, Berlin, NJ 08009 (856) 768-9360

Kelly Miller, Account Manager

Magazine website: Free subscriptions are available

Publisher Cambridge University Press One Liberty Plaza, 20th Floor New York, New York 10006

(212) 337-5000 Circulation: 18,000

Editorial Board Nasim Alem, Penn State University Arlan Benscoter, Lehigh University John Bozzola, Southern Illinois University Peter Crozier, Arizona State University Vinayak Dravid, Northwestern University David Grubb, Cornell University Bryan Huey, University of Connecticut Heather Lowers, U.S. Geological Survey John Mackenzie, North Carolina State Univ. Paul Maddox, U. of North Carolina–Chapel Hill Ania Majewska, U. Rochester Med School Joseph Michael, Sandia National Labs Caroline Miller, Indiana University Brian M. Patterson, Los Alamos National Lab John Reffner, John Jay College, SUNY Ian Robertson, University of Wisconsin Phillip Russell, Appalachian State University Glenn Shipley, Citizen Microscopist Robert Simmons, Georgia State University Bradley Thiel, SUNY Polytechnic Institute Simon Watkins, University of Pittsburgh Cynthia Zeissler, Nat. Inst. of Stds. and Tech. (NIST)

Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76