adsabs/AstroCLIMB huggingface dataset:
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: P–T phase diagram of Fe up to 5000 GPa. Fe is a primary component of Earth and super-Earth cores. It is stable as the body-centered cubic phase (α-Fe) below 820–1000 K at 3–10 GPa, transitioning to the face-centered cubic phase (γ-Fe) above these temperatures. The transformation from γ-Fe to the hexagonal close-packed phase (ϵ-Fe) occurs at 12–82 GPa; the γ–ϵ–liquid triple point is found at 82 GPa and 3300 K. For comparison, phase boundaries from S. Anzellini et al. (2013; dotted line) and R. Boehler (1993; dashed line) are also shown. Data points contributed by static compression experiments, dynamic compression experiments, and computer simulations are marked with circles, triangles, and squares, respectively, and coded with different colors based on the stable phase observed at that P–T condition.
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: Global inversion of the MgO phase diagram (a) with and (b) without potential outliers. Two potential outlier data sets for MgO melting were identified and removed from our inversion, A. Zerr & R. Boehler (1994) and L. Zhang & Y. Fei (2008), which were internally inconsistent with the rest (panel (a)). The low melting temperatures in A. Zerr & R. Boehler (1994) were likely misinterpreted premelting signals (T. Kimura et al. 2017; M. Hou et al. 2021), while the extrapolated curve in L. Zhang & Y. Fei (2008) was biased by FeO-rich liquidus data (O. V. Fat’yanov & P. D. Asimow 2024). Their exclusion has minimal impact on the inversion (panel (b)), likely due to limited low-pressure data. Our preferred melting curve (Figure 5 and panel (a)) places B1-MgO melting at 3900 K (5 GPa), 7300 K (100 GPa), and 9200 K (200 GPa) with a slope of +20–40 K GPa−1, while B2-MgO reaches 12,500 K (500 GPa) and 16,500 K (1000 GPa) with a slope of +9 K GPa−1. Further experiments are needed to validate the low-pressure melting curve (1 bar to 30 GPa).
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: Global inversion algorithm. (a) This global inversion algorithm uses a multiclass logistic model with supervised learning for phase diagram determination (J. Dong et al. 2025). Polynomial functions of P–T are used as log-odds, ﹩f(P,T)={\sum }_{i,j=0}^{n}{\beta }_{i,j}^{k}{P}^{i}{T}^{j}﹩, to estimate the probability of phase stability. The model then selects the phase with the highest probability of being stable at a given P–T. (b) To avoid overfitting, we tune the hyperparameters using supervised learning with L1 lasso regularization. The data set is divided into training and test sets, and the hyperparameters are optimized using a grid search and k-fold cross-validation. The model with the highest F1 score is selected to fit the entire data set and construct the final phase diagram.
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: Model selection and performance of varying complexity for Fe. The phase equilibrium data for Fe are plotted against our phase boundary predictions for degrees 1–4 (solid black lines). F1 scores indicate the performance of the models on the test set, with the degree-2 polynomial model achieving an optimal balance between complexity and performance (highest F1 score). Higher-degree models show diminishing returns owing to overfitting, as indicated by lower F1 scores and minimal improvements in phase boundary predictions.
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: P–T phase diagram of MgSiO3 up to 5000 GPa. MgSiO3 is a first-order approximation of the mantle of Earth and super-Earth exoplanets, since its Mg/Si ratio is close to the solar and bulk Earth values. MgSiO3 has six known major high-pressure polymorphs: orthopyroxene (enstatite, en), clinoenstatite (hpcen), akimotoite (ak), majorite garnet (mj), bridgmanite (bg), and post-perovskite (ppv). Our inversion places the bg–ppv transition at 120 GPa and 2000 K and at 135 GPa and 3100 K, with a slope of +14 MPa K−1. The mj–bg transition occurs at 21 GPa and 2150 K and at 23 GPa and 2550 K, with a slope of +5 MPa K−1. Other transitions include en–hpcen (+3 MPa K−1), hpcen–mj (-3 MPa K−1), and rw+st  ↔  bg (−4 MPa K−1). Data points contributed by static compression experiments, dynamic compression experiments, and computer simulations are marked with circles, triangles, and squares, respectively, and coded with different colors based on the stable phase observed at that P–T condition.
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: P–T phase diagrams of Fe, MgO, SiO2, and MgSiO3 up to 5000 GPa. This figure highlights the relative refractoriness of each material with respect to the P–T conditions at the CMBs of Earth and super-Earth exoplanets, as well as the core conditions of giant planets (Earth CMB: dark green; super-Earth CMB: light green; Uranus and Neptune: blue; Saturn: gold; Jupiter: black). Up to 500 GPa, Fe has the lowest melting temperatures compared to MgO, SiO2, and MgSiO3. Among rocky components, MgSiO3 has the lowest melting temperature below 200 GPa, but above 200 GPa SiO2 becomes the least refractory. Up to 1000 GPa, MgO remains significantly more refractory than Fe, MgO, and MgSiO3. Solid lines indicate globally inverted phase boundaries; dashed and dotted lines represent less constrained boundaries, presented to guide the eye based on the literature.
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: Proposed melting relations for the MgO–SiO2 binary system up to 5000 GPa. The pressure–temperature–composition (P–T–X) phase diagrams of the MgO–SiO2 binary system show its melting behavior, in comparison to that of Fe at (a) 1 bar, (b) 50 GPa, (c) 200 GPa, (d) 2000 GPa, and (e) 5000 GPa. Eutectic points in the T–X diagram indicate the compositions required for the lowest possible melting temperature for the mixture of the two components of a binary joint. (a–c) Between 1 bar and 200 GPa, their eutectic temperatures and compositions are constrained experimentally and through thermodynamic modeling (e.g., N. L. Bowen 1928; C. Liebske & D. J. Frost 2012; N. De Koker et al. 2013; M. A. Baron et al. 2017; S. Ohnishi et al. 2017; K. Ozawa et al. 2018; J. Yao et al. 2021). (d–e) At higher pressures (200–5000 GPa), the phase relations are largely unconstrained, potentially with new silicate phases forming (e.g., MgSi2O5 and Mg2SiO4; T. Tsuchiya & J. Tsuchiya 2011; H. Niu et al. 2015; K. Umemoto et al. 2017; R. Dutta et al. 2022, 2023). The inferred upper bound of the eutectic temperatures for these assemblages, based on the end-members (Figure 11), indicates that the MgO–SiO2 eutectics and the Fe melting curve are likely to intersect between 1000 and 2000 GPa (Section 4.1).
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: P–T phase diagram of SiO2 up to 5000 GPa. SiO2 is a major oxide component of the mantle of Earth and super-Earths. Free SiO2 minerals exist in subducted slabs on Earth and in the mantle of some super-Earth exoplanets. SiO2 has several polymorphs, and its well-studied major phase transitions include coesite to stishovite (coes  ↔  st) at 9–13 GPa, st to post-stishovite or CaCl2-type SiO2 (st  ↔  cacl2, 50–100 GPa), and cacl2 to seifertite (cacl2  ↔  seif) at 125–145 GPa. For comparison, phase boundaries from M. S. Ghiorso (2004; dashed line) and D. Andrault et al. (2022; dotted line) are also shown. Data points contributed by static compression experiments, dynamic compression experiments, and computer simulations are marked with circles, triangles, and squares, respectively, and coded with different colors based on the stable phase observed at that P–T condition.
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: Prevalence of BMOs in the interior of super-Earth exoplanets. Small amounts of iron lower the MgSiO3 melting curve (e.g., L. Stixrude 2014), and iron prefers to partition into the silicate melt with increasing pressure, making a BMO more likely on super-Earths (F. Dragulet & L. Stixrude 2024; V. Lherm et al. 2024). For example, in a super-Earth of 10 M⊕, the MgSiO3 mantle with >30% iron could become less refractory than the Fe core, favoring BMO formation. However, the emergence of new silicate phases at >500 GPa (Figure 9, dashed lines) could suppress BMO formation by steepening the MgSiO3 melting curve (e.g., T. Tsuchiya & J. Tsuchiya 2011; K. Umemoto et al. 2017; R. Dutta et al. 2022, 2023).
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: Global (a) and local (b) inversion of the SiO2 phase diagram. The SiO2 melting curve has been debated, especially at low pressures (≤10 GPa). (a) Our global inversion identifies a melting curve maximum at 12 GPa and 3070 K, followed by a cusp at the coes–st–liquid triple point at 13.4 GPa and 3050 K (Figure 7(a)), consistent with the thermodynamic model of M. S. Ghiorso (2004). This negative melting slope is attributed to a significant volume collapse (∼30%) during the coes–st transition. (b) A focused local inversion limited to data below 30 GPa finds a melting curve maximum at 10 GPa and 3150 K, followed by a cusp at the coes–st–liquid triple point at 12.5 GPa and 3050 K. This local inversion supports a more pronounced negative coes melting curve and better agrees with the data in this P–T range. Amorphization of metastable coes at 25–30 GPa indirectly supports the negative slope of the melting curve, as its extrapolation to 300 K (black dotted line) aligns with the pressures of coes amorphization (blue area; R. J. Hemley et al. 1988; S. Luo et al. 2003).
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: Comparison of true and inverted phase boundaries for synthetic data sets of varying size and fidelity. The rows illustrate the effect of simulated experimental precision, with the top row representing low-precision data (ΔP = ±5 GPa, ΔT = ±1000 K) and the bottom row representing high-precision data (ΔP = ±1 GPa, ΔT = ±200 K). The columns show increasing data size from left to right (n = 10, 100, 1000). Red curves represent the true phase boundaries, while black curves represent the inverted boundaries. As precision and data size increase, the inverted boundaries more accurately recover the true locations of the phase boundaries and their slopes.
Paper: Structure and Melting of Fe, MgO, SiO2, and MgSiO3 in Planets: Database, Inversion, and Phase Diagram
Authors: Junjie Dong, 俊杰 董, Gabriel-Darius Mardaru, Paul D. Asimow, Lars P. Stixrude, Rebecca A. Fischer
Figure caption: Comparison between the global inversion and the thermodynamic model. The solid–solid phase boundaries predicted by the thermodynamic code, HeFESTo (blue lines), and our results (black lines) are in strong agreement, validating the global inversion method. The main differences include the slope of the α–ϵ transition in Fe and the st–cacl2 and cacl2–seif boundaries in SiO2, which are due to the inclusion of additional high-temperature data in our inversion.
Paper: Rover Science Autonomy in Planetary Exploration: Field Analog Tests
Authors: Eldar Z. Noe Dobrea, Maria E. Banks, Roger N. Clark, David Wettergreen, Alberto Candela, Amanda Hendrix, Caitlin Ahrens, Ernie Bell, Abigail Breitfeld, Thomas F. Bristow, Sanlyn Buxner, Margaret Hansen, Gregory M. Holsclaw, Paul Knightly, Georgiana Kramer, Nandita Kumari, Melissa D. Lane, Audrey Martin, McKayla L. Meier, Ruby Patterson, Neil Pearson, Thomas Prettyman, Gregg A. Swayze, David Vaniman, Srinivasan Vijayarangan, Faith Vilas, Shawn P. Wright
Figure caption: Path of the astronauts (white line) during scenario 3 (astronaut/rover collaborative exploration) superposed on a shaded-relief map of the Yellow Cat Flat site (site 3; year 2). Green markers indicate locations of science-team-selected astronaut science stops, locations of astronaut imaging, sample collection, and other activities. The rover traverse is marked with red circles. As can be seen in several locations, particularly the lower portion of the figure, the astronauts were able to navigate to and within topography that could not be traversed by the rover. Simultaneously, the rover was exploring nearby terrain, providing a separate but complementary set of EVA data to the science team. The astronaut and rover met up at several predetermined rendezvous stops for in situ measurements of astronaut-collected samples with rover instruments. Note that, due to operational complications during this scenario, the rover was not able to traverse to some of these points; the rendezvous was alternatively simulated by a member of the rover team and thus is not apparent in the rover traverse shown here. Each day the astronauts returned to a simulated habitat marked with the yellow flag.
Paper: Rover Science Autonomy in Planetary Exploration: Field Analog Tests
Authors: Eldar Z. Noe Dobrea, Maria E. Banks, Roger N. Clark, David Wettergreen, Alberto Candela, Amanda Hendrix, Caitlin Ahrens, Ernie Bell, Abigail Breitfeld, Thomas F. Bristow, Sanlyn Buxner, Margaret Hansen, Gregory M. Holsclaw, Paul Knightly, Georgiana Kramer, Nandita Kumari, Melissa D. Lane, Audrey Martin, McKayla L. Meier, Ruby Patterson, Neil Pearson, Thomas Prettyman, Gregg A. Swayze, David Vaniman, Srinivasan Vijayarangan, Faith Vilas, Shawn P. Wright
Figure caption: Locations of measurements performed by the rover during scenario 2b at Yellow Cat Flat site (site 3; year 2). Yellow diamonds represent measurements performed during traverses; red diamonds represent measurements performed at science stops. Numbers indicate the measurement performed by the rover with the mast-mounted ASD, starting at 0. For clarity, only measurements performed at science stops are indicated by the numbers.
Paper: Rover Science Autonomy in Planetary Exploration: Field Analog Tests
Authors: Eldar Z. Noe Dobrea, Maria E. Banks, Roger N. Clark, David Wettergreen, Alberto Candela, Amanda Hendrix, Caitlin Ahrens, Ernie Bell, Abigail Breitfeld, Thomas F. Bristow, Sanlyn Buxner, Margaret Hansen, Gregory M. Holsclaw, Paul Knightly, Georgiana Kramer, Nandita Kumari, Melissa D. Lane, Audrey Martin, McKayla L. Meier, Ruby Patterson, Neil Pearson, Thomas Prettyman, Gregg A. Swayze, David Vaniman, Srinivasan Vijayarangan, Faith Vilas, Shawn P. Wright
Figure caption: Changes in the relative likelihood of competing geologic origin hypotheses in response to measurements performed by the rover in scenario 2 (rover-directed exploration). (a) Evolution of hypotheses for unit 2. (b) Evolution of hypotheses for unit 3. (c) Evolution of hypotheses for unit 4. Note the rapid growth of the likelihood for the fluvio-lacustrine/marine hypothesis in all cases.
Paper: Rover Science Autonomy in Planetary Exploration: Field Analog Tests
Authors: Eldar Z. Noe Dobrea, Maria E. Banks, Roger N. Clark, David Wettergreen, Alberto Candela, Amanda Hendrix, Caitlin Ahrens, Ernie Bell, Abigail Breitfeld, Thomas F. Bristow, Sanlyn Buxner, Margaret Hansen, Gregory M. Holsclaw, Paul Knightly, Georgiana Kramer, Nandita Kumari, Melissa D. Lane, Audrey Martin, McKayla L. Meier, Ruby Patterson, Neil Pearson, Thomas Prettyman, Gregg A. Swayze, David Vaniman, Srinivasan Vijayarangan, Faith Vilas, Shawn P. Wright
Figure caption: Scenario 2 (rover-directed exploration) final relative probabilities for visited units at the Yellow Cat Flat site 3 (year 2).
Paper: Rover Science Autonomy in Planetary Exploration: Field Analog Tests
Authors: Eldar Z. Noe Dobrea, Maria E. Banks, Roger N. Clark, David Wettergreen, Alberto Candela, Amanda Hendrix, Caitlin Ahrens, Ernie Bell, Abigail Breitfeld, Thomas F. Bristow, Sanlyn Buxner, Margaret Hansen, Gregory M. Holsclaw, Paul Knightly, Georgiana Kramer, Nandita Kumari, Melissa D. Lane, Audrey Martin, McKayla L. Meier, Ruby Patterson, Neil Pearson, Thomas Prettyman, Gregg A. Swayze, David Vaniman, Srinivasan Vijayarangan, Faith Vilas, Shawn P. Wright
Figure caption: Initial relative probabilities, all units.
Paper: Glycine Partitioning in Frozen Putative Europan Brines
Authors: Lucas R. Reynoso, Tuan H. Vu, Robert Hodyss, Paul V. Johnson
Figure caption: Raman spectra of an aqueous solution containing 0.1 M [Na+], 0.1 M [Mg2+], 0.1 M [Cl−], 0.1 M [SO42−], and 0.1 M glycine at 100 K under slow-freezing conditions (red; Table 1, sample 1) and flash-freezing conditions, both before (purple) and after (blue) annealing (Table 1, sample 2). The spectra are offset for clarity and normalized between 0 and 1. Colored bars indicate regions where peak areas were analyzed to generate the 3D spatial distribution maps shown in Figures 2 and 3, with the following assignments: blue—water ice, green—glycine, red—sulfate salt, and yellow—CO2.
Paper: Glycine Partitioning in Frozen Putative Europan Brines
Authors: Lucas R. Reynoso, Tuan H. Vu, Robert Hodyss, Paul V. Johnson
Figure caption: IR spectrum of a glycine-containing Europan analog brine (Table 1, sample 1) after a thermal cycle between 100 and 200 K under ambient air, shown in purple. The inset highlights the region between 2300 and 2375 cm−1, outlined in yellow. For comparison, the red curve represents data from the JWST NIRSpec obtained from a spatial pixel at 46° N, 87° W on Europa, as reported by S. K. Trumbo & M. E. Brown (2023). Labeled peaks indicate the presence of pure CO2 ice (2342 cm−1) and trapped CO2 (2353 cm−1) interpreted from the JWST spectrum.
Paper: Glycine Partitioning in Frozen Putative Europan Brines
Authors: Lucas R. Reynoso, Tuan H. Vu, Robert Hodyss, Paul V. Johnson
Figure caption: 3D Raman maps obtained at 100 K showing the distribution of glycine (green), water ice (blue), and heptahydrate (red) in the flash-frozen brine sample (Table 1, sample 2). In each map, pixel brightness increases with relative abundance (i.e., white pixels are where the component is most abundant).
Paper: Glycine Partitioning in Frozen Putative Europan Brines
Authors: Lucas R. Reynoso, Tuan H. Vu, Robert Hodyss, Paul V. Johnson
Figure caption: Raman spectrum of the brine containing glycine-1-13C (Table 1, sample 3) at room temperature (291 K; red) and upon slow freezing at 100 K (blue). The inset shows an expanded view of the 1200–1450 cm−1 region (yellow box), where the labeled peaks represent vibrational signatures of the Fermi diad modes of CO2.
Paper: Glycine Partitioning in Frozen Putative Europan Brines
Authors: Lucas R. Reynoso, Tuan H. Vu, Robert Hodyss, Paul V. Johnson
Figure caption: 3D Raman maps obtained at 100 K showing the distribution of glycine (green), water ice (blue), epsomite (red), and CO2 in the slow-frozen brine sample (Table 1, sample 1). In each map, pixel brightness increases with relative abundance (i.e., white pixels are where the component is most abundant).
Paper: Glycine Partitioning in Frozen Putative Europan Brines
Authors: Lucas R. Reynoso, Tuan H. Vu, Robert Hodyss, Paul V. Johnson
Figure caption: Pairwise correlation plots of the components within the glycine-brine system, derived from the Raman maps presented in Figures 2 (slow-frozen samples; panels (A), (C), and (E)) and 3 (flash-frozen samples; panels (B) and (D)). Each panel includes a red line that represents the linear fit to the plotted data.
Paper: Curtain-based Maps of Eruptive Activity in Enceladus’s South-polar Terrain at 15 Cassini Epochs
Authors: Joseph N. Spitale, Mattie D. Tigges, Alexander Berne, Alyssa Rhoden, Terry A. Hurford, Kevin D. Webster
Figure caption: Relationship between fault motion and curtain timing. Left: histogram of modeled fault opening (x-axis) relative to frequency that curtains are active (top) and inactive (bottom) (y-axis) over the tidal cycle. Right: similar to the left column but considering strike-slip motion (left- and right- lateral) over fault structures. The x-axis is scaled relative to the maximum value over the tidal cycle. The p-values derived from Kolmogorov–Smirnov tests comparing distributions in either row are shown above the plots. We consider only curtain segments that exhibit significant variability over the tidal cycle (i.e., exhibit a standard deviation greater than zero in Figure 6(c)) for our analysis.
Paper: The 2014–2015 Holuhraun Lava Flow-field in Iceland as a Planetary Analog for Young Volcanic Terrains in Elysium Planitia, Mars
Authors: J. R. C. Voigt, C. W. Hamilton, L. P. Keszthelyi, M. Varnam, S. M. Hibbard, K. M. Stack
Figure caption: Examples of similar lava morphologies at the Holuhraun eruption site in Iceland and Elysium Planitia on Mars. The left panels ((a) and (c)) display the Holuhraun eruption site, captured using the UltraCam-Xp basemap (2015 September 6) with a scale of 20 cm pixel−1. The right panels ((b) and (d)) show Elysium Planitia on Mars, from the Context camera with 6 m pixel−1 resolution. The black arrows in panels (a) and (b) point toward breakouts with a smooth and continuous surface. At Holuhraun (a), spiny lava breaks out of rubbly lava. The white arrows in panels (c) and (d) point to inflation pits. At Holuhraun (c), pits are located within the rubbly facies. The morphological similarities are striking, although the features on Mars are 1 or more orders of magnitude larger.
Paper: The 2014–2015 Holuhraun Lava Flow-field in Iceland as a Planetary Analog for Young Volcanic Terrains in Elysium Planitia, Mars
Authors: J. R. C. Voigt, C. W. Hamilton, L. P. Keszthelyi, M. Varnam, S. M. Hibbard, K. M. Stack
Figure caption: Geological settings and key geographic features at the Holuhraun eruption site. (a) Map of Iceland depicting the major volcanic systems in the neovolcanic zone highlighted in light pink; the Bárðarbunga–Veiðivötn volcanic system is in dark red; central volcanoes are in dark gray with Askja labeled “A” and Bárðarbunga “B”; and the Vatnajökull ice cap is depicted in white. The location of panel (b) is marked with a yellow star. (b) Expanded view of the Holuhraun eruption site from the UltraCam-Xp basemap (2015 September 6), with a pixel scale of 20 cm. The basemap displays the locations of the 2014–2015 Holuhraun lava flow-field, older Holuhraun lava (the hatched area outlined in white), and Askja lava flow-fields. Also shown are the Dyngjusandur/Flæður floodplain, tributaries to the Jökulsá á Fjöllum river system, and the location shown in Figures 3–5.