4th Nassau Mössbauer symposium analysis and summary.- Scientific legacy of Stanley Ruby.- Mössbauer spectroscopy methodology at the cutting-edge of high-pressure research.- Vibrational dynamics of Fe in amorphous Fe-Sc and Fe-Al alloy thin films.- Nuclear Resonance Vibrational Spectroscopy (NRVS) of Fe-S model compounds, Fe-S proteins, and nitrogenase.- On Spin Hamiltonian fits to Mössbauer spectra of high-spin Fe(II) porphyrinate systems.- Mössbauer effect of 151Eu in europium salen complex nanoparticles.- Velocity scales for Mars Mössbauer data.- Nanowires of iron oxides embedded in SiO2 templates.- Nuclear forward scattering vs. conventional Mössbauer studies of atomically tailored Eu-based materials.- A complete solution to the Mössbauer problem, all in one place.- Anisotropic contributions to the transferred hyperfine field studied using a field-induced spin-reorientation.- Use of Mössbauer spectroscopy to determine the effect of salinity on the speciation of triorganotins in Anacostia River sediments.- 57Fe Mössbauer spectroscopic study of (25?x)MnO-xZnO-15Fe2O3-60B2O3 glasses.- Studying surfaces and thin films using Mössbauer spectroscopy.- Variations of BaSnF4 fast ion conductor with the method of preparation and temperature.- The Mössbauer community in the USA.- Two earth years of Mössbauer studies of the surface of Mars with MIMOS II.
"Velocity scales for Mars Mossbauer data (p. 67-68)
David G. Agresti • M. Darby Dyar •
Martha W. Schaefer
Published online: 11 January
2007 © Springer Science + Business Media B.V. 2007
Abstract Raw Mossbauer data acquired from surface rocks and soils by two Mars Exploration Rovers (MERs) are being made available on-line to the general science community for independent analysis and interpretation. The data are released as counts per channel, so a velocity scale must be defined. The Windows-based computer program MERView does this in two steps. In the first, a scale proportional to the true velocity is derived by adjusting the magnitudes of the drive error signal and a phase shift. This report focuses on the second step, in which mm1s units are assigned to the proportional scale by comparing laboratory-measured a-iron peak positions with those of spectra of the internal MER calibration targets. We contrast MERView-derived velocity scales for different MER measurement conditions with the velocity scales provided on-line by the MER team, and conclude that independent velocity calibration is generally desirable.
Key words Mossbauer data Mars· velocitycalibration methodology MER View
1 Introduction
Two Mossbauer spectrometers (MIMOS II) [1] have been operating on the surface of Mars since January 2004 as part of the instrument suite of the Mars Exploration Rovers (MERs) Spirit and Opportunity (http://www.athena.comell.edu/). They have been acquiring spectra of surface rocks and soils in order to contribute to a better understanding of Mars geochemical history, in particular the nature of aqueous processes that may have played a role in defining the observed surface mineralogy.
Analyses of spectral data by the MER Mossbauer team, with inferred mineralogy and interpretations in the geologic context, are presented in several reports [e.g. 2--4]. Given the importance of a full assessment of the data by outside investigators , the general science community is provided with the opportunity for independent analysis by regular releases of the MER data, at roughly 90-day intervals, to two principal web sites, the MER Analysts Notebook at http://anserverl.eprsl.wustl.edu/ and the Planetary Data System (PDS) Geosciences Node at http://pds-geosciences.wustl.edu/.
Mossbauer spectra for each rover are recorded in five detectors in up to thirteen 10-K wide temperature windows «180 K to >290 K), resulting in up to 65 distinct Mossbauer spectra for each sol (Mars day) on which data are recorded. Four detectors record the sample spectra, namely backscatter spectra of surface material, rock, soil, or dust, while detecting 6.4-keV Fe Ko; X-rays and 14.4-keV 57Fe y photons. The fifth detector records in transmission mode the reference spectrum of an internal calibration target consisting of an enriched cc-Fe foil overlaid with enriched a-Fe203 and Fe304.
The raw Mossbauer data for a particular sol, essentially as received from Mars, are embedded in a single 160-kB binarycoded file, the Experimental Data Record (EDR), which also includes other pertinent information such as detector energy spectra, temperature data, and a drive error signal. The structure of the EDR file and the nature of the binary coding are described in a Software Interface Specification document, available on line. Most important for this report is that the Mossbaucr data are provided as counts versus channel, requiring calibration of the velocity scale to mm/s versus channel, which may be accomplished with use of the drive error signal and the properties of the calibration target."
