@article{74e79970c12146d8aa50e09688e60f39,
title = "Analysis of Active Neutron Measurements From the Mars Science Laboratory Dynamic Albedo of Neutrons Instrument: Intrinsic Variability, Outliers, and Implications for Future Investigations",
abstract = "The Dynamic Albedo of Neutrons (DAN) instrument onboard Mars Science Laboratory uses neutron die-away, an active nuclear spectroscopy technique, to measure the abundance and depth distribution of hydrogen and neutron-absorbing elements (e.g., Fe and Cl) in the top ∼0.5 m of the Mars subsurface. We examined the intrinsic variability in neutron die-away data using simulated DAN measurements with a range of compositions relevant to equatorial and high-latitude environments on Mars. Our analysis shows that the total neutron counts and timing of neutron arrival explain most variability in thermal neutron die-away curves for a DAN-like instrument configuration over homogeneous subsurfaces. We analyzed the variability in thermal neutron die-away across a variety of elemental compositions that might be observed by DAN or future instruments. We found that when H concentration is low (e.g., in equatorial regions including Gale crater), neutron die-away is most sensitive to variations in H. Conversely, when H concentration is high (e.g., in poleward regions of Mars or icy bodies), neutron die-away is most sensitive to variations in neutron absorbers. We estimated that the H and neutron absorber concentrations in DAN measurements acquired Sols 1–2080 in Gale crater and found that most measurements had low H and moderate absorber content. We presented an outlier analysis of these measurements to identify targets with high potential scientific impact and found that most outliers along the traverse corresponded with abnormally low or high neutron absorber content measurements, some of which may be associated with high-silica fracture-associated halos and felsic igneous material.",
keywords = "Mars, Mars Science Laboratory, machine learning, nuclear spectroscopy, outlier detection, statistical analysis",
author = "Kerner, {H. R.} and Hardgrove, {C. J.} and S. Czarnecki and Gabriel, {T. S.J.} and Mitrofanov, {I. G.} and Litvak, {M. L.} and Sanin, {A. B.} and Lisov, {D. I.}",
note = "Funding Information: We acknowledge the Dynamic Albedo of Neutrons instrument team and the broader Mars Science Laboratory team. The authors would like to thank Jack Lightholder of the Jet Propulsion Laboratory for their contributions to the DAN data processing pipeline at ASU, Roger Wiens of Los Alamos National Laboratory for his input on outlier interpretation, Heni Ben Amor of Arizona State University for his input on outlier detection, and Fred Calef of the Jet Propulsion Laboratory for providing localizations for DAN measurements. The authors would also like to thank the anonymous reviewers whose suggestions improved previous versions of this paper. This work was supported by the Mars Science Laboratory Participating Scientist Program, Award NNN12AA01C. Computational support was provided by the Research Computing Center at Arizona State University. Data used in this study are publicly available through the NASA Planetary Data System (PDS) and can be accessed at https://doi.org/10.5281/zenodo.3592014 . Funding Information: We acknowledge the Dynamic Albedo of Neutrons instrument team and the broader Mars Science Laboratory team. The authors would like to thank Jack Lightholder of the Jet Propulsion Laboratory for their contributions to the DAN data processing pipeline at ASU, Roger Wiens of Los Alamos National Laboratory for his input on outlier interpretation, Heni Ben Amor of Arizona State University for his input on outlier detection, and Fred Calef of the Jet Propulsion Laboratory for providing localizations for DAN measurements. The authors would also like to thank the anonymous reviewers whose suggestions improved previous versions of this paper. This work was supported by the Mars Science Laboratory Participating Scientist Program, Award NNN12AA01C. Computational support was provided by the Research Computing Center at Arizona State University. Data used in this study are publicly available through the NASA Planetary Data System (PDS) and can be accessed at https://doi.org/10.5281/zenodo.3592014. Publisher Copyright: {\textcopyright}2020. American Geophysical Union. All Rights Reserved.",
year = "2020",
month = may,
day = "1",
doi = "10.1029/2019JE006264",
language = "English (US)",
volume = "125",
journal = "Journal of Geophysical Research: Planets",
issn = "2169-9097",
publisher = "Wiley-Blackwell Publishing Ltd",
number = "5",
}