Thermal Emission Imaging System Research Articles

Spectroscopy of Magnesium Sulfate Double Salts and Their Implications for Mars Exploration

Magnesium sulfate has been widely detected on the surface of Mars. The occurrence of magnesium sulfate and mixed cationic sulfates preserves clues regarding the sedimentary environment, hydrological processes, and climate history of ancient Mars. In this study, seven magnesium sulfate double salts were synthesized in the laboratory using a high-temperature solid phase reaction or slow evaporation of aqueous solutions. The samples were analyzed using X-ray diffraction to confirm their phase and homogeneity. Subsequently, the Raman, mid-infrared spectra, and visible near-infrared spectra of these samples were collected and analyzed. Our results showed that the spectra of the analyzed magnesium sulfate double salts exhibited distinctive spectral features. These laboratory results may provide new insights for the identification of various magnesium sulfate double salts on Mars during the interpretation of in situ data collected by Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC), SuperCam, and the ExoMars Raman Laser Spectrometer (RLS). In addition, the MIR and VNIR spectra features obtained in this study provide an improved reference and spectra library for decipherment of data sourced from the Thermal Emission Spectrometer (TES), Thermal Emission Imaging System (THEMIS), and Mars Mineralogical Spectrometer (MMS).

Martian Gravity Waves Observed by the Thermal Emission Imaging System (THEMIS) During Northern Summer

AbstractMartian gravity waves (GW) greatly impact the atmospheric circulation and formation of clouds, but many GW observations of the lower atmosphere are confined to specific orientations and wavelengths, leaving many gaps in the continuum of waves. To overcome the issue, we analyze eight Mars years of data during the season of Ls = 120°–150° from Band 10 (14.9 µm) of the Thermal Emission Imaging System (THEMIS), sensitive to GWs at ∼25 km altitude. All horizontal orientations at wavelengths below ∼40 km are detectable, with the potential to detect north‐south oriented GWs up to ∼1,000 km in length. Most THEMIS observations have brightness temperature variances compatible with GW disturbances. Intense GW activity concentrates poleward of 60°S, with normalized magnitudes up to 10−4 K2 K−2; activity decreases toward the equator and remains low throughout the northern hemisphere. The interannual intensity of GWs varies by latitude within three regimes of GW length: short (<20 km), medium (20–100 km), and long (>100 km). Gravity wave orientations that are detectable in all directions do not favor a single direction; that is, Martian GWs at 25 km altitude are isotropic. Finally, interannual variability seems to emerge from interactions with dust storms, orography, and planetary waves.

Surface Energy Budget, Albedo, and Thermal Inertia at Jezero Crater, Mars, as Observed From the Mars 2020 MEDA Instrument

AbstractThe Mars Environmental Dynamics Analyzer (MEDA) on board Perseverance includes first‐of‐its‐kind sensors measuring the incident and reflected solar flux, the downwelling atmospheric IR flux, and the upwelling IR flux emitted by the surface. We use these measurements for the first 350 sols of the Mars 2020 mission (Ls ∼ 6°–174° in Martian Year 36) to determine the surface radiative budget on Mars and to calculate the broadband albedo (0.3–3 μm) as a function of the illumination and viewing geometry. Together with MEDA measurements of ground temperature, we calculate the thermal inertia for homogeneous terrains without the need for numerical thermal models. We found that (a) the observed downwelling atmospheric IR flux is significantly lower than the model predictions. This is likely caused by the strong diurnal variation in aerosol opacity measured by MEDA, which is not accounted for by numerical models. (b) The albedo presents a marked non‐Lambertian behavior, with lowest values near noon and highest values corresponding to low phase angles (i.e., Sun behind the observer). (c) Thermal inertia values ranged between 180 (sand dune) and 605 (bedrock‐dominated material) SI units. (d) Averages of albedo and thermal inertia (spatial resolution of ∼3–4 m2) along Perseverance's traverse are in very good agreement with collocated retrievals of thermal inertia from Thermal Emission Imaging System (spatial resolution of 100 m per pixel) and of bolometric albedo in the 0.25–2.9 μm range from (spatial resolution of ∼300 km2). The results presented here are important to validate model predictions and provide ground‐truth to orbital measurements.

MC-UNet: Martian Crater Segmentation at Semantic and Instance Levels Using U-Net-Based Convolutional Neural Network

Crater recognition on Mars is of paramount importance for many space science applications, such as accurate planetary surface age dating and geological mapping. Such recognition is achieved by means of various image-processing techniques employing traditional CNNs (convolutional neural networks), which typically suffer from slow convergence and relatively low accuracy. In this paper, we propose a novel CNN, referred to as MC-UNet (Martian Crater U-Net), wherein classical U-Net is employed as the backbone for accurate identification of Martian craters at semantic and instance levels from thermal-emission-imaging-system (THEMIS) daytime infrared images. Compared with classical U-Net, the depth of the layers of MC-UNet is expanded to six, while the maximum number of channels is decreased to one-fourth, thereby making the proposed CNN-based architecture computationally efficient while maintaining a high recognition rate of impact craters on Mars. For enhancing the operation of MC-UNet, we adopt average pooling and embed channel attention into the skip-connection process between the encoder and decoder layers at the same network depth so that large-sized Martian craters can be more accurately recognized. The proposed MC-UNet is adequately trained using 2∼32 km radii Martian craters from THEMIS daytime infrared annotated images. For the predicted Martian crater rim pixels, template matching is subsequently used to recognize Martian craters at the instance level. The experimental results indicate that MC-UNet has the potential to recognize Martian craters with a maximum radius of 31.28 km (136 pixels) with a recall of 0.7916 and F1-score of 0.8355. The promising performance shows that the proposed MC-UNet is on par with or even better than other classical CNN architectures, such as U-Net and Crater U-Net.

Simplified Automatic Atmospheric Correction for THEMIS Infrared Data

Thermal infrared spectral data from the Thermal Emission Imaging System (THEMIS) on Mars Odyssey can provide diagnostic information to characterize Martian surface compositions. Accurately isolating the atmospheric contribution from the thermal radiance of THEMIS data is essential for surface mineralogy analysis. In this work, we present improved semi-automatic and fully automated tools to simplify the traditional atmospheric correction method for THEMIS data. Both methods use the Thermal Emission Spectrometer surface emissivity data but in different ways. These two methods are applied to several locations that have been well documented in previous studies, to assess their capability of determining surface spectral features. The fully automatic method demonstrates its simplicity, viability, and robustness by which more consistent results have been generated for the same area across multiple THEMIS images and for areas with large topographic gradients. The tools developed in this work will broaden the utilization of THEMIS infrared spectral data to the wider planetary science community.

Distribution and Morphology of Lava Tube Systems on the Western Flank of Alba Mons, Mars

AbstractIntegrated analyses of Thermal Emission Imaging System (THEMIS) IR, Context Camera (CTX), and Mars Orbiter Laser Altimeter (MOLA) data sets have been used to characterize the western flank of the Martian volcano Alba Mons, which hosts a prominent population of lava tube systems. Identification and mapping of lava tube systems is based on both morphologic and topographic analyses, including the presence of chains of collapse depressions and elongate, sinuous ridges. Lava tubes and adjacent tabular lava flows with lengths of 100+ km form an extensive lava flow field. Analyses of topographic data sets, including slope maps, suggest continuity of the radial flow field pattern across the full western flank. Concurrent surface activity across the western flank is consistent with age constraints from geologic mapping and crater size‐frequency distributions that indicate Early Amazonian ages. The mapped population of 331 lava tube systems in the western flank geologic map quadrangle has a mean length of 36.2 km and a total length of ∼12,000 km. Individual lava tube systems extend up to ∼400 km. Orientation and slope data for lava tube systems show small deviations compared to regional values in 50‐km grid cells defined by the MOLA Digital Elevation Model, suggesting a strong coupling of lava tubes to the current slopes of Alba Mons. Mapping of lava tube systems documents segments both showing collapse and with no collapse, indicating the potential for extensive subsurface cavities that would be important astrobiological targets.

Geologic Context of the Bright MARSIS Reflectors in Ultimi Scopuli, South Polar Layered Deposits, Mars

AbstractRadar‐bright basal reflectors have been detected below the South Polar Layered Deposits (SPLD), using Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) data and have an exciting but controversial interpretation: liquid water from subglacial lakes. We mapped the surface of the SPLD immediately above and surrounding the putative lakes (1:2M map scale) in order to provide a geologic context for the interpretation of bright basal reflectors. We use Thermal Emission Imaging System daytime IR (100 m/pixel), Context Camera (6 m/pixel), and High Resolution Imaging Science Experiment (25 cm/pixel) data to characterize geologic units and typical surface roughness. We find evidence for multiple geologic units with features due to CO2 and aeolian‐related processes. We do not find evidence for surface modification linked to postulated lake locations. This is not consistent with the interpretation of the MARSIS basal radar reflector as subglacial lakes.

Machine learning as a tool to classify extra-terrestrial landslides: A dossier from Valles Marineris, Mars

Many researchers studied Martian landslides, and most of these studies are in the Valles Marineris (VM). Those studies are mainly morphologic analysis, estimates of landslide deposit volumes, thermal properties of the landslides, spectral analyses, and mapping and classifying landslides. But, this study created a robust landslide inventory of 682 incidents by collation of data from different sources, apart from our own mapping. This mapping was done for the completeness and accuracy of the landslide inventory. This inventory consists of 141 debris flows, 291 rock avalanches, and 250 slumps. This classification was based on the available literature, and these landslides covered Hebes, Ophir, Candor, Melas, Coprates, Ius and Tithonium chasmas. Landslides were mapped with the aid of images from Mars Reconnaissance Orbiter (MRO) Context Camera (CTX), Mars Orbiter Mission (MOM) Mars Colour Camera (MCC), and high-resolution Google Mars. Digital Elevation Model (DEM) from the Mars Express (MEX) High-Resolution Stereo Camera (HRSC), Thermal Inertia (TI) from Thermal Emission Imaging System (THEMIS), and available geological map were used to define 15 critical parameters of the landslide inventory viz., length (L), width (W), relative relief (RR), area, L/W ratio, RR/L ratio, TI of landslide (mean, minimum, maximum), and slope statistics (mean, minimum, maximum), TI of the scarp, the slope of the scarp, and geology. These 15 parameters were subjected to a multicollinearity testing, which excluded the dependent variable TI (mean). Further, the rest of the variables were analyzed using multiple discriminant analysis (MDA), where the parameters RR/L, L/W, and RR showed higher canonical discriminant function coefficients of 1.245, 0.461 and 0.159, respectively, suggesting that these are the parameters that primarily discriminates the landslides. The classification of landslides was evaluated using a 10-fold cross-validation method using different machine learning algorithms. The five models that provided the best results are simple logistic, logistic regression, meta-classifier, multi-layer perceptron, and Sequential Minimal Optimization (SMO). Of these, simple logistics has the maximum classification accuracy of 81.09%. Thus, this study demonstrates the potential of using machine learning models to classify extra-terrestrial landslides, especially the long-runout landslides that are characteristics of other planets and satellites.

Insight Into Formation Processes of Layered Ejecta Craters on Mars From Thermophysical Observations

AbstractUnderstanding the morphological characteristics of craters that are indicative of their formation environment can provide insight into surface geology. Layered ejecta (LE) craters, found on Mars and some other planetary bodies, have been hypothesized to have formed as a result of either interaction with subsurface volatiles (volatile fluidization model) and/or with the atmosphere (atmospheric entrainment model). Formation of LE craters by either model should result in different grain size distributions throughout the ejecta deposit. Using thermal inertia to infer surface properties, we investigated LE craters and their ejecta deposits in an effort to distinguish between possible LE formation processes on Mars. We used thermophysical properties of crater ejecta to determine grain size distribution, to model horizontal mixtures and vertical layering, and to identify materials present within the ejecta. We assessed the thermal properties of 50 uniformly sampled LE craters using Mars Odyssey Thermal Emission Imaging System (THEMIS) and Mars Global Surveyor Thermal Emission Spectrometer (TES) data. Our THEMIS analysis identifies 12 craters with grain size distributions consistent with the volatile fluidization model, 3 craters that have characteristics potentially associated with either model, and 22 craters that do not exhibit characteristics matching either model. Our TES analysis identifies 11 craters with characteristics consistent with the volatile fluidization model and 8 craters that are consistent with the atmospheric entrainment model. While some observations of grain size distributions provide evidence for either or both models, there is not overwhelming support for either model, potentially due to uncertainties of derived thermal inertia data.

Investigating Sources of Spectral Olivine Enrichments in Martian Bedrock Plains Using Diurnal Emissivity Changes in THEMIS Multispectral Images

AbstractWe investigate spectral olivine detections in the Noachian cratered highlands that are spatially associated with flat bedrock exposures. Strong olivine detections were previously attributed to relatively high (∼10%–15%) modal abundances of olivine in the bedrock, and then later hypothesized to instead originate from a patchy cover of olivine‐rich sediment formed from erosional lag deposits and mineral‐specific comminution/transport. We test these hypotheses by developing a new technique to partially separate the spectral signals of bedrock and unconsolidated surficial sediment. It uses the differing thermophysical properties of sand and indurated materials, which change the relative contributions of these materials to the emitted spectrum over the diurnal cycle. We use multispectral Mars Odyssey Thermal Emission Imaging System (THEMIS) observations collected in the mid‐afternoon and early evening to apply this technique to eight Terra Sabaea bedrock plains and the Nili Fossae olivine‐carbonate plain. Significant changes in spectral shape arising from compositional differences between bedrock and sediment cover are observed in four bedrock plains. Where these differences are observed, the spectral changes are consistent decreased olivine abundance in the sediment fraction, rather than increased as previously hypothesized. Our results indicate that bedrock materials in the Terra Sabaea region are olivine‐rich in composition, likely indicating a pyroclastic origin for these materials.

Thermophysical and Compositional Analyses of Dunes at Hargraves Crater, Mars

Abstract We analyze thermal emission spectra using the 2001 Mars Odyssey Thermal Emission Imaging System and the Mars Global Surveyor Thermal Emission Spectrometer to characterize grain size and mineralogical composition of dunes at Hargraves crater, Mars. Thermal inertia and bulk composition of the dunes were compared to inferred provenances from the thermal infrared response of surface constituent materials. We use a Markov Chain Monte Carlo technique to estimate the bulk amount of mineralogy contributed by each inferred provenance to the dune field composition. An average thermal inertia value of 238 ± 17 Jm−2 K−1 s−0.5 was found for the dunes, corresponding to a surface composed of an average effective grain size of ∼391 ± 172 μm. This effective particle size suggests the presence of mostly medium sand-sized materials mixed with fine and coarse grain sands. The dunes are likely composed of a weakly indurated surface mixed with unconsolidated materials. Compositional analysis specifies that the dunes are composed of a mixture of feldspar, olivine, pyroxene, and relatively low bulk-silica content. Dune materials were likely derived from physical weathering, especially aeolian erosion, predominantly from the crater ejecta unit at the crater, mixed with a small amount from the crater floor and crater rim and wall lithologies—indicating that the dune materials were likely sourced locally.

Thermophysical Properties and Surface Heterogeneity of Landing Sites on Mars From Overlapping Thermal Emission Imaging System (THEMIS) Observations

AbstractOrbitally derived thermal inertia (TI) values of surfaces allow for remote interpretation of rock and sediment physical characteristics. The evolving local times of the Mars Odyssey Thermal Emission Imaging System (THEMIS) mission have enabled surface temperature data collection over multiple seasons and local times over ∼9 Mars years (MY). We utilize this higher temporal resolution data set to separate TI values of individual materials within THEMIS pixels (100 m sampling). In this study, we focus on geologic units within Gusev, Gale, and Jezero crater landing sites to determine their respective TI and ground‐truth our methods. We use the KRC model to predict temperatures for a range of homogeneous and two‐component thermophysical mixing scenarios (laterally and vertically heterogeneous), and compare those to THEMIS brightness temperatures. The Gusev and Gale crater results are consistent with rover‐based evaluations, indurated or clast‐covered sands. The best‐fit scenarios along the Jezero crater volcanic floor unit show low to moderate TI values representative of coarse sediment, volcaniclastic, or pyroclastic rocks. The light toned unit and western fan deposits both indicate sands and a moderate TI component; we interpret this as heavy fracturing within the rock. Difficulties in modeling some THEMIS temperatures are attributed to daily weather effects, local atmospheric dust variability, and real surface changes over time (e.g., dust deposition and removal); we also observe that some temperature observations lead to non‐unique modeled physical solutions. Nevertheless, these methods can still rule out a significant range of material properties and provide meaningful geologic information about Mars’ surface.

Geologic and Thermal Characterization of Oxia Planum Using Mars Odyssey THEMIS Data

AbstractOxia Planum will be the landing site for the European Space Agency ExoMars 2022 “Rosalind Franklin” mission to conduct astrobiological and geological experiments investigating the region's past. Previous orbital short‐wave infrared (SWIR, 1.0–2.6 μm) spectroscopic studies reported widespread phyllosilicate detections in the region suggesting possible alteration of its original lithology by past aqueous activity. We used thermal infrared data (TIR, 6.8–14.8 μm) from the Thermal Emission Imaging System to assess regional bulk composition and thermophysical properties. We coupled these assessments with SWIR spectral analyses from the Compact Reconnaissance Imaging Spectrometer for Mars and with high‐resolution visible images to characterize the physical properties of the region. We cataloged four geologic units with varying spectral, thermophysical, and textural properties. The previously mapped phyllosilicate bearing materials are associated with our oldest mapped unit. This unit exhibits light/dark‐toned interbedding and TIR spectral characteristics consistent with phyllosilicate dominated and/or intermediate volcanic lithologies; evidence for mafic materials is lacking. Superposing that unit is a thin patchy dark‐toned unit that contains mafic signatures. Isolated locations within the region are superposed by a mechanically competent, rough unit that lacks mafic signatures and is interpreted as lava or well‐cemented fluvial deposits. The uppermost mapped unit is an eroded fan of possible deltaic or alluvial origin, with an inferred surface composition of unconsolidated sediment. Finally, based on stratigraphic and cross‐cutting relationships with ejecta from Kilkhampton crater nearby, we suggest that all units formed during or before the Early Hesperian period.

Semiautomated Identification and Characterization of Dunes at Hargraves Crater, Mars

AbstractThe Mars Global Digital Dune Database (MGD3) contains information on Martian dune fields and prepared manually from the Thermal Emission Imaging System (THEMIS; 100 m/pixel) images. Although the MGD3 outlines dune fields, it overlooks the recognition of smaller dune forms. This paper aims to identify individual dunes from a semiautomated object‐based image analysis technique and characterize dune materials at Hargraves crater, Mars. MGD3 would benefit to be updated for an improved understanding of the Martian surface and its atmospheric mechanisms at a local scale. An object‐based image analysis technique was applied here to the Context Camera (CTX; 6 m/pixel) data set to extract dune data in a more efficient, reliable, and accurate fashion. This study is a test case in validating a remote sensing method that has wide applicability to the entire Martian surface resulting in an update to the dune database at a higher spatial resolution—providing a better understanding of surface and atmospheric behavior of Mars at the local scale. We also explored the wind flow and dune stability—presenting an insight into the dune modification mechanism—within the crater. The prevailing wind inside the crater flows to the west‐northwest. The dunes are labeled as active (stability index of 2) and do not appear to have been influenced by subsurface water ice or volatiles. We emphasize that the technique used here has a wide prospect in temporal monitoring of dune sediment flux, dune migration or erosion rates, improving near‐surface airflow modeling, and dune stability analysis.

Remote characterization of physical surface characteristics of Mars using diurnal variations in apparent thermal inertia

Analysis of the Martian surface today can provide insight into the processes that may have affected it over its history. Information about the physical surface characterization of a region can help determine the degree of sorting it has experienced and/or its geologic maturity. Sub-resolved, horizontal “checkerboard” mixtures of materials with different thermal inertias can lead to differences in the apparent thermal inertia values inferred from night and day radiance observations. Standard methods for deriving thermal inertia from orbit via the THermal EMission Imaging System (THEMIS) can give values for the same location that vary by as much as 20% between images. Such methods assume that each pixel contains material of a single, uniform thermal inertia. Here, it is proposed that if a mixture of low and high thermal inertias is present within a pixel, the apparent thermal inertia inferred will be biased toward the thermal inertia of whichever component of the surface is warmer at the time of the measurement. This effect will result in a variation in apparent thermal inertia values inferred from measurements taken at different times of day and night. Therefore, a correlation is hypothesized between the magnitude of diurnal variations in apparent thermal inertia values and the degree of non-uniformity of thermal inertias present within a given pixel location.This work shows that the magnitude of such diurnal variation in apparent thermal inertias is sufficient to detect geologically useful differences in surfaces mixtures both theoretically and through in-situ analysis. Mapping the difference in apparent thermal inertias from day and night THEMIS observations may prove to be a new way of distinguishing surfaces that have relatively uniform thermal inertias from those that have horizontally-mixed thermal inertias. Note that this study makes no attempt to characterize the effects of vertical (subsurface) inhomogeneity on apparent thermal inertia, which could also be important for some locations.

Deriving Surface Ages on Mars Using Automated Crater Counting

AbstractImpact craters on solar system bodies are used to determine the relative ages of surfaces. The smaller the limiting primary crater size, the higher the spatial resolution in surface/resurfacing age dating. A manually counted database (Robbins & Hynek, 2012, https://doi.org/10.1029/2011JE003966) of >384,000 craters on Mars >1 km in diameter exists. But because crater size scales as a power law, the number of impact craters in the size range 10 m to 1 km is in the tens of millions, a number making precise analysis of local variations of age, over an entire surface, impossible to perform by manual counting. To decode this crater size population at a planetary scale, we developed an automated Crater Detection Algorithm based on the You Only Look Once v3 object detection system. The algorithm was trained by annotating images of the controlled Thermal Emission Imaging System daytime infrared data set. This training data set contains 7,048 craters that the algorithm used as a learning benchmark. The results were validated against the manually counted database as the ground truth data set. We applied our algorithm to the Thermal Emission Imaging System global mosaic between ±65° of latitude, returning a true positive detection rate of 91% and a diameter estimation error (~15%) consistent with typical manual count variation. Importantly, although a number of automated crater counting algorithms have been published, for the first time we demonstrate that automatic counting can be routinely used to derive robust surface ages.

Lava filling of Gale crater from Tyrrhenus Mons on Mars

Gale crater shows infilling of lava of basaltic origin mainly coming from the south via Farah Vallis. Using available Thermal Emission Imaging System (THEMIS) images, Mars Orbiter Laser Altimeter (MOLA) topographic data, Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) mineralogical data, and geochemical analyses taken in situ by the Mars Science Laboratory (MSL) in different locations of the crater, we focused on the possible origin and the main path of the lava that filled Gale crater. We found that: 1) the K/Ar age of the basaltic rocks on Gale's floor is consistent with the age of formation of Tyrrhenus Mons derived from the southern polar giant impact (SPGI) model; 2) the Aeolis Mensae region does not show evidence for interaction between lava coming from the north (Elysium Mons) and lava coming from the south (Tyrrhenus Mons); 3) the geomorphological analysis shows that Farah Vallis is the convergence of a complex network of volcanic channels that can be tracked back to the lava fields of Tyrrhenus Mons; 4) a one-dimensional model of lava along the observed path, using an Adirondrack basalt composition for the substrate, shows that lava from Tyrrhenus Mons is thermally capable of flowing the entire distance to Gale before cooling down. This evidence is consistent with the lava fill observed at Gusev crater.

New Insights of Geomorphologic and Lithologic Features on Wudalianchi Volcanoes in the Northeastern China from the ASTER Multispectral Data

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imaging system onboard NASA’s (National Aeronautics and Space Administration’s) Terra satellite is capable of measuring multispectral reflectance of the earth’s surface targets in visible and infrared (VNIR) to shortwave infrared (SWIR) (until 2006) as well as multispectral thermal infrared (TIR) regions. ASTER VNIR stereo imaging technique can provide high-resolution digital elevation models (DEMs) data. The DEMs data, three-dimensional (3D) perspective, and ratio images produced from the ASTER multispectral data are employed to analyze the geomorphologic and lithologic features of Wudalianchi volcanoes in the northeastern China. Our results indicate that the 14 major conical volcanic craters of Wudalianchi volcanoes are arranged as three sub-parallel zones, extending in a NE (Northeast) direction, which is similar to the direction of regional fault system based on the ASTER DEMs data. Among the 14 volcanic craters in Wudalianchi, the Laoheishan, and Huoshaoshan lavas flows, after the historic eruptions, pouring down from the crater, partially blocked the Baihe River, which forms the Five Large Connected Pools, known as the Wudalianchi Lake. Lithologic mapping shows that ASTER multispectral ratio imagery, particularly, the Lava Flow Index (LFI) (LFI = B10/B12) imagery, can clearly distinguish different lava flow units, and at least four stages of volcanic eruptions are revealed in the Wudalianchi Quaternary volcano cluster. Thus, ASTER multispectral TIR data can be used to determine relative dating of Quaternary volcanoes in the semi-arid region. Moreover, ASTER 3D perspective image can present an excellent view for tracking the flow directions of different lavas of Wudalianchi Holocene volcanoes.

Assessing electric vehicle policy with region-specific carbon footprints

This study contributes to better understanding the interregional variability in vehicle carbon footprints and presents a case study of China’s electric vehicle (EV) charging infrastructure promotion plan (EVSE2020). Based on an integrated hybrid life-cycle assessment (LCA) with new regional electricity mixes and the Thermal Emission Imaging System (THEMIS) model with local inventories, the carbon footprints of battery electric vehicles (BEVs) and internal combustion engine vehicles (ICEVs) are calculated for all size segments. For the A-class segment, the most popular size segment, the results show that the carbon footprint of ICEVs is approximately 250.6 gCO2e/km. The BEV carbon footprint under a nationwide electricity mix is 217.6 gCO2e/km and ranges between 104.4 (Yunnan) and 265.7 (Shandong) gCO2e/km. These results can be explained by the proportion of coal in provincial electricity consumption mixes (10% to 90%). Out of the 31 provinces in mainland China, A-class BEVs driven in 26 provinces will reduce life-cycle greenhouse gas (GHG) emissions compared to ICEVs. In addition, the maximum BEV carbon footprint exceeds the minimum by 79%–121% owing to size segments, which is much higher than that for ICEVs, 59%. The interprovincial variability in vehicle carbon footprints calls for modifications to the interregional priority assignments in the EVSE2020 plan, which currently focuses on air pollution control and economic status. After incorporating explicit considerations of climate mitigation, this study recommends raising the level of priority of three provinces in Central and Southwest China (Sichuan, Chongqing, and Hubei) in the EVSE2020 plan. For provinces with a high share of coal-based electricity, the development of BEVs of small size segments (A00/A0) should be encouraged.

The Unusual Thermophysical and Surface Properties of the Daedalia Planum Lava Flows

AbstractDaedalia Planum contains numerous young lava flows with diverse flow morphology. Previous thermal infrared studies avoided this region because of the moderately high visible albedo, assumed to be caused by optically thick dust, and overall low thermal inertia. The Daedalia Planum flows, however, have some of the roughest surfaces on Mars and display an unusual thermophysical behavior that most likely indicates different areal percentages of dust, sand, and lava outcrops. Recent studies suggest that these surfaces contain significant proportions of lava outcrops rising above low‐lying regions of sand with a spatially discontinuous dust layer. A multi‐instrument, multispectral approach combined with prior morphological mapping is applied here to discriminate between individual flows and determine the variation of thermophysical units on the surface. High‐resolution ConTeXt Camera and High‐Resolution Imaging Science Experiment data are used to investigate the flow surfaces and degree of mantling. Thermal Emission Imaging System and Thermal Emission Spectrometer thermal infrared data are analyzed to quantify the thermophysical variations between flows, identify surfaces with minimally mantled lava outcrops, and apply a thermophysical classification to differentiate the surface units. The results demonstrate that the observed thermal variations are due to different distributions of blocky lavas and sand infill. A majority of lava flows with rough surfaces display a diurnal and thermal inertia response indicative of a larger areal percentage of those outcrops versus that of sand and dust. This approach identifies surfaces with more exposed lava outcrops, promising targets for future composition analysis, in regions previously thought to be too dusty for such studies using thermal infrared data.