Dr Kevin Olsen

Abstract:

MoonTools is a software framework, written in the Julia programming language [9], allowing straightforward, flexible, and performant processing of multispectral and hyperspectral data products. Designed originally to operate on M3 observations [4, 5], our framework is readily extensible to a wide range of datasets.Drawing from functional programming [6], our framework emphasizes composition of disparate operations. Processing pipelines are constructed in native Julia, parametrised by partial function application. This approach allows for flexibility of use and ease of extensibility, and distinguishes our work from similar tools, e.g. [7]; further, Julia’s just-in-time compilation  and parallel-programming tools allow for fast, multithreaded operations on multi-terabyte datasets, including for user-supplied inputs.Implemented operations include thermal and photometric corrections of multispectral radiance cubes, reflectance retrievals, spectral parameter determination, and post-processing amongst others. Additional utilities allow users to search datasets for targets by nomenclature, terrain type, and local solar time. Various dataset export options are available, including HDF5 products and “at a glance” views of regions of interest.We provide an example Julia pipeline in Listing 1, reproducing the detection of spinel at Theophilus crater [1,2]. We begin by importing the MoonTools package; then, we define a RATIO parameter expression. The spectral parameters SPINEL and PYROXENE are implemented as in [2] up to a constant factor using the RATIO definition. Invoked macros produce multithreaded CPU and GPU-kernel implementations of these parameters transparently to the user. Finally, a pipeline is composed: we search M3 data for observations of Theophilus crater, apply parameters, and produce “quicklook” plots of all matching observations; one such plot is shown in Figure 1.Listing 1: Pipeline invocation, including parameter definitions, required to produce Figure 1.using MoonTools@paramdef RATIO(λs, R; λ1, λ2) = sum(R[λ1]) / sum(R[λ2])@param SPINEL   RATIO [1400]       [1750]@param PYROXENE RATIO [0700, 1200] [0950]observations(:m3) > by_name("Theophilus") > PYROXENE > SPINEL > quicklookFigure 1: One of several quicklook outputs, showing Theophilus crater. Quicklooks are intended to provide overviews of regions of interest (RoIs) indicated by pipeline construction. Plots on the left include a reference narrowband reflectance, and PYROXENE and SPINEL parameter maps across the RoI. The RoI is partitioned into a 3x3 grid of zones; spectra sampled from each zone are plotted on the right in corresponding positions.Striping artifacts exist throughout the M3 dataset, and are prominent in spectral parameter products; state-of-the-art tooling must destripe these images [7,8]. We provide a bespoke destriping algorithm using a wavelet packet decomposition [3]. The modified pipeline is given in Listing 2; a destriped spinel map is shown in Figure 2.Listing 2: Pipeline altered from Listing 1; outputs are shown in Figure 2.observations(:m3) > by_name("Theophilus") > SPINEL > destripe!Figure 2: Destriped spinel parameter map. The before and after of the destriping operation are shown in the left and center plots; the removed signal is shown on the right.Software development is progressing rapidly. We anticipate a release of MoonTools to the scientific community in the coming months; MoonTools will be distributed under the terms of an open-source software license. We will welcome bug reports, feature requests, and contributions.References[1] Dhingra, D., Pieters, C.M., Boardman, J.W., Head, J.W., Isaacson, P.J. and Taylor, L.A., 2011. Compositional diversity at Theophilus Crater: Understanding the Geological Context of Mg‐Spinel-Bearing Central Peaks. Geophysical Research Letters, 38(11).[2] Pieters, C.M., Hanna, K.D., Cheek, L., Dhingra, D., Prissel, T., Jackson, C., Moriarty, D., Parman, S. and Taylor, L.A., 2014. The distribution of Mg-spinel across the Moon and constraints on crustal origin. American Mineralogist, 99(10), pp.1893-1910.[3] Mallat, S., 1999. A Wavelet Tour of Signal Processing. Elsevier.[4] Chandrayaan-1 Moon Mineralogy Mapper Science Team (2011). M3 L1B Gridded Spectral Radiance, Version 3. PDS Cartography and Imaging Sciences Node. https://doi.org/10.17189/1520248.[5] Chandrayaan-1 Moon Mineralogy Mapper Science Team (2011). L2 Gridded Spectral Reflectance (version 1) products. https://doi.org/10.17189/1520414.[6] Backus, J., 1978. Can Programming be Liberated from the von Neumann Style? A Functional Style and its Algebra of Programs. Communications of the ACM, 21(8), pp.613-641.[7] Suárez‐Valencia, J.E., Rossi, A.P., Zambon, F., Carli, C. and Nodjoumi, G., 2024. MoonIndex, an open‐source tool to generate spectral indexes for the moon from M3 data. Earth and Space Science, 11(6), p.e2023EA003464.[8] Shkuratov, Y., Surkov, Y., Ivanov, M., Korokhin, V., Kaydash, V., Videen, G., Pieters, C. and Stankevich, D., 2019. Improved Chandrayaan-1 M3 data: A northwest portion of the Aristarchus Plateau and contiguous maria. Icarus, 321, pp.34-49.[9] Bezanson, J., Karpinski, S., Shah, V.B. and Edelman, A., 2012. Julia: A Fast, Dynamic Language for Technical Computing. arXiv preprint arXiv:1209.5145.

Abstract:

The ExoMars Trace Gas Orbiter (TGO) has characterised trace gases in the Martian atmosphere over several Mars years, improving the accuracy of species concentration measurements and observing temporal, vertical and spatial variations. Hydrogen chloride—detected for the first time with TGO [1,2]—has been investigated recently using the mid-infrared channel on the Atmospheric Chemistry Suite (ACS MIR). HCl observations show a strong seasonal variation, with almost all of the detections occurring during the latter half of the year (solar longitudes 180-360°) in the dusty season, when water vapour is present in the Martian atmosphere and ozone concentrations are low. Chlorine-bearing species such as HCl are important to understand in Mars’ atmosphere because on Earth they are involved in numerous processes throughout the planetary system, including volcanism, and they play a key role in atmospheric chemistry, e.g., by influencing concentrations of oxidative species such as oxygen (O2) and ozone (O3).Here, we use the Mars Planetary Climate Model—a 3-D global climate model that includes a photochemical network—to explore the atmospheric HCl observations. We build on existing chlorine photochemical networks [3,4] to investigate potential source and sink mechanisms, focusing in particular on heterogeneous chemistry involving ice aerosols, and exploring the possibility of its role in direct release of HCl to the atmosphere. We also explore how chlorine species are affected indirectly by changes in the abundances of oxidative species (e.g., OH and HO2,and by extension, O and O3),driven by heterogeneous chemistry. Understanding the role of oxidative chemistry on HCl and other trace gases is key to achieving a more complete picture of processes occurring in the present-day Mars atmosphere, as well as processes that have shaped its evolution and habitability.[1] Korablev O. I. et al. (2021). Sci. Adv., 7, eabe4386. [2] Olsen K. S. et al. (2021). Astron. Astrophys., 647, A161. [3] Rajendran, K. et al. (2025). JGR: Planets 130(3), p.e2024JE008537. [4] Streeter, P. M. et al. (2025). GRL 52(6), p.e2024GL111059.

Abstract:

Plain Language Summary: Hydrogen chloride is a gas emitted by volcanoes on Earth. It has been hunted on Mars as a sign of recent volcanic activity, and was found with the ExoMars Trace Gas Orbiter (TGO), whose main objective is to find rare gases in the Martian atmosphere that tell us about biological or geological activity there. This commentary examines the recent results presented by Faggi et al. (2025), https://doi.org/10.1029/2025je009105 on a campaign to measure HCl in the Martian atmosphere from the Earth. From a telescope on Earth, the measurements cover the whole surface of Mars revealing how HCl is distributed and how that changes over a year. Here, we discuss the context of these results and their implications for chlorine deposits seen on the surface.

Abstract:

Some oxidized compounds in Martian soils may form through heterogeneous electrochemistry (HEC) stimulated by electrostatic discharge (ESD) during dust storms and dust devils. To test this hypothesis, we conducted medium-strength ESD experiments in a Mars simulation chamber and analyzed the Cl, O, and C isotopic compositions of the resulting chloride, (per)chlorate, and carbonate products. These ESD products exhibit substantial mass-dependent depletions in heavy isotopes: ε 37Cl from -11.3 ‰ to +2.0 ‰, ε 18O from -34.5 ‰ to -12.9 ‰, and ε 13C around -11.4 ‰. These results, when compared with isotopic measurements from recent Mars missions (ESA’s ExoMars Trace Gas Orbiter and the Sample Analysis at Mars (SAM) instrument package aboard NASA’s Curiosity rover) and Martian meteorites, indicate that HEC induced by Martian dust activities can account for a substantial portion of the (per)chlorates and carbonates identified at the surface of Mars.