A new method for atmospheric correction and de-noising of CRISM hyperspectral data

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¹Yuki Itoh,¹Mario Parente
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.114024]
¹Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, United States of America
Copyright Elsevier

We propose a new method to perform atmospheric correction and de-noising on hyperspectral image cubes acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board NASA’s Mars Reconnaissance Orbiter (MRO). The CRISM imager has had an important role in advancing our understanding of many aspects of Martian mineralogy. Many mineral detections from CRISM data have been facilitated by significant efforts in the development of the CRISM data processing pipeline to retrieve surface reflectance. However, some residuals remain in CRISM spectra after atmospheric correction, causing difficulty in the interpretation of processed reflectance spectra. In addition, CRISM images are occasionally corrupted with high noise levels exhibiting heterogeneous statistical properties. This paper identifies the cause of such spectral distortions and describe a technique that simultaneously performs both atmospheric correction and de-noising for each image cube individually. In particular, our method focuses on the 1.0–2.6 m wavelength region of CRISM images and is applicable to images of non-icy surfaces. Experimental results show that our technique is able to significantly mitigate noise and distortions from various sources like gaseous absorptions, detector temperature, and water ice aerosols, compared with the atmospheric correction method in the CRISM official processing pipeline called volcano scan correction, for a variety of scenes. Careful validations that include the qualitative examination of noise and artifacts both on ratioed and non-ratioed spectra and comparison using multiple overlapping images strengthen confidence in our approach.

Composition and origin of L5 Trojan asteroids of Mars: Insights from spectroscopy

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¹Apostolos A.Christou,^1,2Galin Borisov,³Aldo Dell’Oro,⁴Alberto Cellino,⁵Maxime Devogèle
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.113994]
¹Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, United Kingdom
²Institute of Astronomy and NAO, 72 Tsarigradsko Chaussée Blvd, Sofia BG-1784, Bulgaria
³INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, Firenze I-50125, Italy
⁴INAF – Osservatorio Astrofisico di Torino, via Osservatorio 20, Pino Torinese 10025, Italy
⁵Lowell Observatory, 1400 W Mars Hill RD, Flagstaff, AZ 86001, USA
Copyright Elsevier

We investigate the mineralogical makeup of L5 Martian Trojan asteroids via reflectance spectroscopy, paying special attention to (101429) 1998 VF₃₁, the only L5 Trojan that does not belong to the Eureka family (Christou, 2013). We find that this asteroid most likely belongs to the Bus-Demeo S-complex, in agreement with Rivkin et al. (2007). We compare it with a variety of solar system bodies and obtain good spectral matches with Sq- or S-type asteroids, with spectra of the lunar surface and of Martian and lunar meteorites. Mixture fitting to spectral endmembers suggests a surface abundance of Mg-rich orthopyroxene and iron metal or, alternatively, a combination of plagioclase and metal with a small amount of Mg-poor orthopyroxene. The metallic component may be part of the intrinsic mineral makeup of the asteroid or an indication of extreme space weathering.

In light of our findings, we discuss a number of origin scenarios for (101429). The asteroid could be genetically related to iron-rich primitive achondrite meteorites (Rivkin et al., 2016), may have originated as impact ejecta from Mars – a scenario proposed recently for the Eureka family asteroids (Polishook et al., 2017) – or could represent a relic fragment of the Moon’s original solid crust, a possibility raised by the asteroid’s close spectral similarity to areas of the lunar surface. If, on the other hand, (101429) is a relatively recent addition to the Martian Trojan clouds (Christou et al., 2020), its origin is probably traced to high-inclination asteroid families in the Inner Main Belt.

For the olivine-dominated Eureka family, we find that the two smaller asteroids in our sample are more spectrally similar to one another than to (5261) Eureka, the largest family member. Spectral profiles of these three asteroids are closely similar shortward of ∼0.7 μ m but diverge at longer wavelengths. For the two smaller asteroids in particular, we find the spectra are virtually identical in the visible region and up to 0.8 μ m. We attribute spectral differences in the near-IR region to differences in either: degree of space weathering, olivine chemical composition and/or regolith grain size.

Coordinated EDX and micro‐Raman analysis of presolar silicon carbide: A novel, nondestructive method to identify rare subgroup SiC

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¹Nan Liu,²Andrew Steele,¹Larry R. Nittler,³Rhonda M. Stroud,³Bradley T. De Gregorio,¹Conel M. O’D. Alexander,¹Jianhua Wang
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13555]
¹Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington, District of Columbia, 20015 USA
²Geophysical Laboratory, Carnegie Institution for Science, Washington, District of Columbia, 20015 USA
³Materials Science and Technology Division, US Naval Research Laboratory, Washington, District of Columbia, 20375–5320 USA
Published by arrangement with John Wiley & Sons

We noticed a few minor errors in Table S2 in the supplement of the original manuscript, as summarized below. (1) The error for the 14N/15N ratio of grain M2‐A4‐G27 should be 0.2 instead of 0.3. (2) The δ30Si value of grain M1‐A5‐G1112 should be 16 instead of 19. (3) The names of grains M2‐A1‐G569 and M2‐A1‐G576 should be M2‐A2‐G569 and M2‐A1‐G576‐2, respectively. This erratum contains the correct data table (Table S2).

In addition, we would like to note that the isotope ratios for grains M1‐A4‐G557 and M2‐A1‐G303 reported in Table S2 are slightly different from those reported in Liu et al. (2017), due to small differences in the adopted regions of interest (ROIs) for data reduction. The use of different ROIs and slightly different normalization approaches also resulted in small differences between the silicon isotope ratios of X grains reported in Table S2 and in Liu et al. (2018). The two sets of data, however, generally overlap with each other within 1σ errors, and the small differences do not affect any of the discussions or conclusions in these papers.

Mineralogy, geochemistry and classification of the new smolenice iron meteorite from Slovakia

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¹Gargulák, M.,²Ozdín, D.,³Povinec, P.P.,^4,5Strekopytov, S.,^6,7Timothy Jull, A.J.,³Sýkora, I.,⁹Porubčan, V.,¹⁰Farsang, S.
Geologica Carpathica 71, 221-232 Link to Article [DOI: 10.31577/GeolCarp.71.3.2]
¹State Geological Institute of Dionýz Štúr, Mlynská dolina 1, Bratislava 11, 817 04, Slovakia
²Comenius University, Faculty of Natural Sciences, Department of Mineralogy and Petrology, Ilkovičova 6, Bratislava 4, 842 15, Slovakia
³Comenius University, Faculty of Mathematics, Physics and Informatics, Department of Nuclear Physics and Biophysics, Mlynská dolina, Bratislava, 842 48, Slovakia
⁴Natural History Museum, Imaging and Analysis Centre, Cromwell Road, London, SW7 5BD, United Kingdom
⁵National Measurement Laboratory, LGC, Queens Road, Teddington, TW11 0LY, United Kingdom
⁶University of Arizona, Department of Geosciences, Tucson, AZ 85721, United States
⁷Isotope Climatology and Environmental Research Centre, Hungarian Academy of Sciences, Institute for Nuclear Research, Debrecen, 4026, Hungary
⁸Astronomical Institute, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, 845 04, Slovakia
⁹University of Cambridge, Department of Earth Sciences, Downing Street, Cambridge, CB2 3EQ, United Kingdom