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Spectral features of olivine across the intermediate infrared region (IMIR, 4–8 μm) shift systematically with iron‐magnesium content, enabling determination of olivine composition. Previous IMIR studies have used laboratory data with signal‐to‐noise ratios (SNRs) and spectral resolutions potentially greater than those of data derived from planetary missions. Here we employ a feature fitting algorithm to quantitatively assess the influence of data quality on olivine detection and compositional interpretation from IMIR data of 29 spectra of pure olivine of synthetic, terrestrial, lunar, and Martian origins, as well as 5 spectra of lunar pyroclastic beads measured as bulk samples. First, we demonstrate the effectiveness of the feature fitting algorithm in the interpretation of IMIR olivine spectra, predicting olivine composition with an average error of 6.4 mol% forsterite across all test spectra using laboratory‐quality data. We then extend this analysis to degraded test spectra with reduced SNRs and sampling rates and find a range of data qualities required to predict olivine composition within ±11 Mg# (molar Mg/[Mg + Fe] × 100) for the test spectra explored here. Spectra for the sample most relevant to lunar exploration, an Apollo 74002 drive tube consisting of microcrystalline olivine and glass‐rich pyroclastics, required SNRs ≥ 200 for sampling rates ≤25 nm to predict composition within ±11 Mg# of the sample's true composition. Derived limits on SNRs and sampling rates will serve as valuable inputs for the development of IMIR spectrometers, enabling comprehensive knowledge of olivine composition on the lunar surface. Plain Language Summary: An understanding of olivine composition can reveal the history of large‐ and small‐scale magmatic processes, offering key insights into a planet's thermal and chemical evolution. Here we explore olivine spectra in the intermediate infrared region (IMIR), where systematic trends in olivine's absorption bands are indicative of composition. We degrade laboratory olivine spectra to data qualities that are more realistic of spectrometers used in planetary exploration and derive constraints on the signal‐to‐noise ratio and sampling rates required to accurately predict olivine composition. These constraints will be useful in the development of IMIR spectrometers. Key Points: We use a feature fitting routine to predict olivine composition from degraded spectral data in the intermediate infrared region (4–8 μm)Accurate prediction of olivine composition is observed at data qualities expected of spectrometers designed for space exploration [ABSTRACT FROM AUTHOR]

Several mineralogically diverse regions across Mars are capped by dark‐toned rock formations emplaced during the Noachian‐Hesperian transition, an era encompassing a shift in volcanism from dominantly explosive to effusive. However, these caprocks' origins are uncertain, limiting insight into the nature of this shift. We explore the potential volcanic ash origin of a widespread (∼50,000 km2) mafic caprock in the Circum‐Isidis region via an integrated photogeologic and remote‐compositional analysis. We also investigate whether this unit is genetically equivalent to a mafic rock formation exposed in the floor of Jezero Crater. We find: (a) the Jezero Floor and Capping Units are morphologically, stratigraphically, and compositionally similar, suggesting a shared formation mechanism, and (b) the tonal layering and draping characteristics of the Capping Unit are most consistent with a volcanic ash origin atop the ultramafic Olivine‐Rich Unit, also an ash. Our hypotheses can be tested by the Perseverance rover and studies of returned samples. Plain Language Summary: In its early history, Mars volcanism transitioned from explosive to lava style eruptions. We test hypotheses for the origins of a rock formation overlying the region surrounding Perseverance rover, finding this unit is most likely a volcanic ash. We also test whether this rock unit is exposed specifically in Jezero Crater, the current location of the Perseverance rover. We find that this unit not only is equivalent to the rock formation that Perseverance landed on but also may aid in understanding the causes behind Mars' volcanic transformation ∼3 billion years ago. Key Points: Compositional and photogeologic data suggest Jezero's crater‐retaining floor and the regional Capping Unit are equivalent geologic unitsCharacteristics of this widespread mafic unit are most consistent with a volcanic ashfall origin atop the Olivine‐Rich unit, also an ashSame origin for both prompts consideration of whether they represent products of related eruptions during Mars' global volcanic shift [ABSTRACT FROM AUTHOR]

Olivine ([Mg,Fe]2SiO4) has been remotely detected on numerous solar system bodies, but its composition has been only partially constrained using visible‐near infrared (VNIR, 0.5–3 μm) and midinfrared (MIR, 8–15 μm) spectra. Meanwhile, the spectral character of olivine in the "cross‐over" region of the infrared (4–8 μm) remains generally unexplored. We examine the relationship between olivine Mg# (molar Mg/[Mg + Fe] × 100) and the wavelength positions of two strong, discrete overtone‐combination bands at ~5.6 and ~6.0 μm. In reflectance and thermal emission spectra measured for 47 synthetic and natural olivine samples that span the Mg‐Fe solid solution, we find that the 5.6 and 6.0 μm bands shift systematically to longer wavelengths by 0.11 and 0.10 μm, respectively, with increasing Fe content. Our results indicate that olivine Mg# may be determined within ±10 mol% forsterite using the positions of these two bands, making "cross‐over" region spectroscopy a potentially powerful remote sensing tool. Key Points: Olivine spectra in the 4–8 μm wavelength range exhibit distinct bands associated with strong molecular vibrations at longer wavelengthsA compositionally diverse suite of olivine exhibits systematic trends in 4–8 μm spectral band positions over the Mg‐Fe solid solutionSpectra acquired in the 4–8 μm range provide a new tool for compositional assessment and remote sensing [ABSTRACT FROM AUTHOR]

Silica has the highest demonstrated potential of any phase to preserve microfossils on Earth and therefore may host potential biosignatures on Mars. We detected hydrated silica in Jezero crater, the landing site of the National Aeronautics and Space Administration's Mars 2020 rover mission, by applying Dynamic Aperture Factor Analysis/Target Transformation to images from the Compact Reconnaissance Imaging Spectrometer for Mars. Hydrated silica detections with Dynamic Aperture Factor Analysis/Target Transformation were verified using commonly accepted Compact Reconnaissance Imaging Spectrometer for Mars analysis methods. The morphology of geologic units associated with silica was characterized with high‐resolution imaging. Several hypotheses are presented for the formation environment of hydrated silica. All are testable via in situ investigation. We assess the likelihood of silica to preserve biosignatures in these different scenarios based on habitability considerations and biosignature preservation in Earth analog environments and materials. Also reported are possible detections of hydrated silica in the Nili Fossae basement and olivine‐rich units, as well as Al‐phyllosilicate within Jezero crater. Key Points: Hydrated silica is detected in Jezero crater and could have formed in a variety of environments with different degrees of habitabilityHydrated silica is associated with smooth dark‐toned material that covers the olivine‐rich unitHydrated silica in Jezero crater is an excellent target for in situ investigation for biosignatures [ABSTRACT FROM AUTHOR]