Martian spectral units derived from ISM imaging spectrometer data

Based on results of the Viking mission, the soil layer of Mars has been thought to be fairly homogeneous and to consist of a mixture of as few as two components, a 'dark gray' basaltic material and a 'bright red' altered material. However, near-infrared reflectance spectra measured recently both telescopically and from spacecraft indicate compositional heterogeneity beyond what can be explained by just two components. In particular, data from the ISM imaging spectrometer, which observed much of the equatorial region at a spatial resolution of approximately 22 km, indicate spatial differences in the presence and abundance of Fe-containing phases, hydroxylated silicates, and H2O. The ISM data was used to define, characterize, and map soil 'units' based on their spectral properties. The spatial distribution of these 'units' were compared to morphologic, visible color, and thermal inertia features recognized in Viking data

Spectrally distinct ejecta in Syrtis Major, Mars: Evidence for environmental change at the Hesperian-Amazonian boundary

Analysis of visible and near-infrared (VNIR) imaging spectrometer data of the Syrtis Major volcanic complex on Mars shows spectrally distinct ejecta (SDE) around a subset of the region's impact craters. We explore the nature of this spectral difference with the intention of constraining the physical cause of the distinction and the significance of their near random spatial distribution. Crater counting performed by Baratoux et al. (2007) indicated that the craters with SDE are systematically younger than craters without SDE. Extensive crater counts of the craters with SDE show that they fit a consistent Hartmann (2005) isochron indicting that they represent temporally continuous population. This population was dated near 2 Ga, consistent with the counts of Baratoux et al. (2007). This modeled age corresponds to just after the Hesperian-Amazonian boundary, indicating that it may be related to a global event. We explore possible explanations for the lack of SDE around older craters, including atmospheric changes, significant but brief regional emplacement of materials, and volcanic activity. We conclude that the preferred explanation is that the SDE represent the true composition of the Syrtis Major volcanics and that surfaces older than 2 Ga were altered by interactions with water vapor or volcanic gases under different Hesperian climatic and atmospheric conditions leading to all craters formed after this alteration event to display SDE

Dynamic aperture factor analysis/target transformation (DAFA/TT) for Mg-serpentine and Mg-carbonate mapping on Mars with CRISM near-infrared data

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lin, H., Tarnas, J. D., Mustard, J. F., Zhang, X., Wei, Y., Wan, W., Klein, F., & Kellner, J. R. Dynamic aperture factor analysis/target transformation (DAFA/TT) for Mg-serpentine and Mg-carbonate mapping on Mars with CRISM near-infrared data. Icarus, 355, (2021): 114168, https://doi.org/10.1016/j.icarus.2020.114168.Serpentine and carbonate are products of serpentinization and carbonation processes on Earth, Mars, and other celestial bodies. Their presence implies that localized habitable environments may have existed on ancient Mars. Factor Analysis and Target Transformation (FATT) techniques have been applied to hyperspectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) to identify possible serpentine and Mg-carbonate-bearing outcrops. FATT techniques are capable of suggesting the presence of individual spectral signals in complex spectral mixtures. Applications of FATT techniques to CRISM data thus far only evaluate whether an entire analyzed image (≈ 3 × 105 pixels) may contain spectral information consistent with a specific mineral of interest. The spatial distribution of spectral signal from the possible mineral is not determined, making it difficult to validate a reported detection and also to understand the geologic context of any purported detections. We developed a method called Dynamic Aperture Factor Analysis/Target Transformation (DAFA/TT) to highlight the locations in a CRISM observation (or any similar laboratory or remotely acquired data set) most likely to contain spectra of specific minerals of interest. DAFA/TT determines the locations of possible target mineral spectral signals within hyperspectral images by performing FATT in small moving windows with different geometries, and only accepting pixels with positive detections in all cluster geometries as possible detections. DAFA/TT was applied to a hyperspectral image of a serpentinite from Oman for validation testing in a simplified laboratory setting. The mineral distribution determined by DAFA/TT application to the laboratory hyperspectral image was consistent with Raman analysis of the serpentinite sample. DAFA/TT also successfully mapped the spatial distribution of Mg-serpentine and Mg-carbonate previously detected in CRISM data using band parameter mapping and extraction of ratioed spectra. We applied DAFA/TT to CRISM images in some olivine-rich regions of Mars to characterize the spatial distribution of Mg-serpentine and Mg-carbonate-bearing outcrops.This work was supported by the National Natural Science Foundation of China (grant no. 41671360, 41525016, 41902318). JFM and JDT acknowledge NASA support through a subcontract from the Applied Physics Lab for CRISM investigations. H. Lin also acknowledges the support from the key research Program of the Institute of Geology and Geophysics, CAS (IGGCAS-201905). The Headwall imaging spectrometer was acquired using funds to JRK from The Institute at Brown for Environment and Society and Brown University. The DAFA/TT codes are available on GitHub (https://github.com/linhoml?tab=repositories)

Morphology and Distribution of Volcanic Vents in the Orientale Basin from Chandrayaan-1 Moon Mineralogy Mapper (M3) Data

One of the most fundamental questions in the geological and thermal evolution of the Moon is the nature and history of mantle melting and its relationship to the formation and evolution of lunar multi-ringed basins. Mare volcanic deposits provide evidence for the nature, magnitude and composition of mantle melting as a function of space and time [1]. Many argue that mantle partial melts are derived from depths well below the influence of multiringed basin impact events [1], while others postulate that the formation of these basins can cause mantle perturbations that are more directly linked to the generation ascent and eruption of mare basalts [2,3]. In any case, longer-term basin evolution will considerably influence the state and orientation of stress in the lithosphere, and the location of mare volcanic vents in basins as a function of time [4]. Thus, the location, nature and ages of volcanic vents and deposits in relation to multi-ringed impact basins provides evidence for the role that these basins played in the generation of volcanism or in the influence of the basins on surface volcanic eruption and deposit concentration. Unfortunately, most lunar multi-ringed impact basins have been eroded by impacts or filled with lunar mare deposits [5-8], with estimates of the thickness of mare fill extending up to more than six km in the central part of some basins [9-11]. The interior of most basins (e.g., Crisium, Serenitatis, Imbrium, Humorum) are almost completely covered and obscured. Although much is known about the lava filling of multi-ringed basins, and particularly the most recent deposits [5-8], little is known about initial stages of mare volcanism and its relationship to the impact event. One multi-ringed basin, Orientale, offers substantial clues to the relationships of basin interiors and mare basalt volcanism

Influences of increasing temperature on Indian wheat: quantifying limits to predictability

As climate changes, temperatures will play an increasing role in determining crop yield. Both climate model error and lack of constrained physiological thresholds limit the predictability of yield. We used a perturbed-parameter climate model ensemble with two methods of bias-correction as input to a regional-scale wheat simulation model over India to examine future yields. This model configuration accounted for uncertainty in climate, planting date, optimization, temperature-induced changes in development rate and reproduction. It also accounts for lethal temperatures, which have been somewhat neglected to date. Using uncertainty decomposition, we found that fractional uncertainty due to temperature-driven processes in the crop model was on average larger than climate model uncertainty (0.56 versus 0.44), and that the crop model uncertainty is dominated by crop development. Simulations with the raw compared to the bias-corrected climate data did not agree on the impact on future wheat yield, nor its geographical distribution. However the method of bias-correction was not an important source of uncertainty. We conclude that bias-correction of climate model data and improved constraints on especially crop development are critical for robust impact predictions