Identification and quantification of diffuse fresh submarine groundwater discharge via airborne thermal infrared remote sensing

Airborne thermal infrared (TIR) overflights were combined with shoreline radionuclide surveys to investigate submarine groundwater discharge (SGD) along the north shore of Long Island, NY between June 2013 and September 2014. Regression equations developed for three distinct geomorphological environments suggest a positive linear relationship between the rate of diffuse SGD and the spatial extent of the observed coastal TIR anomalies; such a relationship provides quantitative evidence of the ability to use TIR remote sensing as a tool to remotely identify and measure SGD. Landsat TIR scenes were unable to resolve any of the 18 TIR anomalies identified during the various airborne overflights. Two locations were studied in greater detail via 222Rn time series and manual seepage meters in order to understand why specific shoreline segments did not exhibit a TIR anomaly. SGD at the first site, located within a large, diffuse TIR anomaly, was composed of a mixture of fresh groundwater and circulated seawater with elevated levels of nitrate. In contrast, SGD at the second site, where no coastal TIR anomaly was observed, was composed of circulated seawater with negligible nitrate. Despite the compositional differences in seepage, both sites were similar in discharge magnitude, with average time series 222Rn derived SGD rates equal to 18 and 8 cm d−1 for the TIR site and non-TIR site, respectively. Results suggest that TIR remote sensing has the ability to identify locations of a mixture between diffuse fresh and circulated seawater SGD. If TIR anomalies can be demonstrated to represent a mixture between fresh and circulated seawater SGD, then the cumulative area of the TIR anomalies may be used to estimate the fresh fraction of SGD relative to the cumulative area of the seepage face, and thus allows for improved SGD derived nutrient flux calculations on a regional scale

Visible, Near-Infrared, and Mid-Infrared Spectral Characterization of Hawaiian Fumarolic Alteration Near Kilauea's December 1974 Flow: Implications for Spectral Discrimination of Alteration Environments on Mars

The December 1974 flow in the SW rift zone at Kilauea Volcano, Hawaii, has been established as a Mars analog due to its physical, chemical, and morphological properties, as well as its interaction with the outgassing plume from the primary Kilauea caldera. We focus on a solfatara site that consists of hydrothermally altered basalt and alteration products deposited in and around a passively degassing volcanic vent situated directly adjacent to the December 1974 flow on its northwest side. Reflectance spectra are acquired in the visible/near-infrared (VNIR) region and emission spectra in the mid-infrared (MIR) range to better understand the spectral properties of hydrothermally altered materials. The VNIR signatures are consistent with silica, Fe-oxides, and sulfates (Ca, Fe). Primarily silica-dominated spectral signatures are observed in the MIR and changes in spectral features between samples appear to be driven by grain size effects in this wavelength range. The nature of the sample coating and the thermal emission signatures exhibit variations that may be correlated with distance from the vent. Chemical analyses indicate that most surfaces are characterized by silica-rich material, Fe-oxides, and sulfates (Ca, Fe). The silica and Fe-oxide-dominated MIR/VNIR spectral signatures exhibited by the hydrothermally altered material in this study are distinct from the sulfate-dominated spectral signatures exhibited by previously studied low-temperature aqueous acid-sulfate weathered basaltic glass. This likely reflects a difference in open vs. closed system weathering, where mobile cations are removed from the altered surfaces in the fumarolic setting. This work provides a unique infrared spectral library that includes martian analog materials that were altered in an active terrestrial solfatara (hydrothermal) setting. Hydrothermal environments are of particular interest as they potentially indicate habitable conditions. Key constraints on the habitability and astrobiological potential of ancient aqueous environments are provided through detection and interpretation of secondary mineral assemblages; thus, spectral detection of fumarolic alteration assemblages observed from this study on Mars would suggest a region that could have hosted a habitable environment

Thank You to Our 2020 Peer Reviewers

International audiencePeer reviewing is the selfless act of evaluating and providing feedback on scientific papers submitted in journals like JGR: Planets. Every review is written with the objective of clarifying the article and often contains suggestions for additional analyses or topics of discussion. Reviewers often spend hours examining the rigor of the methods, the validity of the results, and the significance of the conclusions in the submitted manuscripts. The extra effort of our pool of reviewers in a year when we all needed to adjust our daily routines in response to a pandemic has not gone unnoticed. In 2020, JGR: Planets benefited from 1,168 reviews provided by 705 unique reviewers. We are particularly grateful to the scientists who remained involved in the review process. We also understand that many of us had to reduce our reviewing commitment this year. Hopefully, the coming year will see a return to normalcy in your lives. To our reviewers, past, present, and future, the entire editorial board of JGR: Planets wishes to express here our most heartfelt gratitude. Thank you

Solar Albedo High Resolution Global Map of the Martian Surface from OMEGA/MEX

International audienceWe present a global map of solar albedo derived from OMEGA data. It is the highest resolution map of this key parameter for climate modelling and TI retrievals

Vapor‐Deposited Minerals Contributed to the MartianSurface During Magmatic Degassing

Abstract Martian magmas were likely enriched in S and Cl with respect to H2O. Exsolution of a vapor phase from these magmas and ascent of the gas bubbles through the magma plumbing system would have given rise to shallow magmas that were gas‐charged. Release and cooling of this gas from lava flows during eruption may have resulted in the addition of a significant amount of vapor‐deposited phases to the fines of the surface. Experiments were conducted to simulate degassing of gas‐charged lava flows and shallow intrusions in order to determine the nature of vapor‐deposited phases that may form through this process. The results indicate that magmatic gas may have contributed a large amount of Fe, S, and Cl to the Martian surface through the deposition of iron oxides (magnetite, maghemite, and hematite), chlorides (molysite, halite, and sylvite), sulfur, and sulfides (pyrrhotite and pyrite). Primary magmatic vapor‐deposited minerals may react during cooling to form a variety of secondary products, including iron oxychloride (FeOCl), akaganéite (Fe3+O (OH,Cl)), and jarosite (KFe3+ 3(OH)6(SO4)2). Vapor‐deposition does not transport significant amounts of Ca, Al, or Mg from the magma and hence, this process does not directly deposit Ca‐ or Mg‐sulfates

In Recognition of Our 2021 Peer Reviewers

International audiencePeer reviewing is the key to ensuring that the articles published in scientific journals such as JGR: Planets are based on sound scientific principles, follow state-of-the-art techniques, and present exciting discoveries or novel understanding of the fundamental processes that affect solar system objects. Our journal covers an extraordinarily broad range of topics addressing every aspect of geoscience with the only requirement that the work should not be solely focused on the Earth. Our editorial team in 2021 comprised Gareth Collins, Jun Cui, Joel Davis, Caleb Fassett, Leigh Fletcher, Matthias Grott, Ananya Mallik, German Martínez, Molly McCanta, Ryan Park, Andrew Poppe, Beatrix Sanchez-Cano, Mariek Schmidt, Yasuhito Sekine, Kelsi Singer, Sonia Tikoo, David Trang, and Zhiyong Xiao, in addition to the authors of this note. No matter how eclectic, our team cannot be specialized in every subject. With the universe as our playground, we rely on the expertise of the community to vet the articles submitted to the journal. In 2021, JGR: Planets benefited from 951 reviews provided by 597 unique reviewers. We also received help from 25 guest editors working on 5 active special collections. We know that most juggle many duties, both professional and personal. We are forever grateful that they chose to dedicate their time and energy to evaluating submitted manuscripts and advising us on the suitability of each manuscript for our journal, often suggesting ways to improve the paper. Scientific publishing truly is a community effort. The entire editorial board of JGR: Planets wishes to express here our most heartfelt gratitude to the many scientists who chose to support this journal, their journal. Thank you

Groundwater activity on Mars and implications for a deep biosphere

By the time eukaryotic life or photosynthesis evolved on Earth, the martian surface had become extremely inhospitable, but the subsurface of Mars could potentially have contained a vast microbial biosphere. Crustal fluids may have welled up from the subsurface to alter and cement surface sediments, potentially preserving clues to subsurface habitability. Here we present a conceptual model of subsurface habitability of Mars and evaluate evidence for groundwater upwelling in deep basins. Many ancient, deep basins lack evidence for groundwater activity. However, McLaughlin Crater, one of the deepest craters on Mars, contains evidence for Mg-Fe-bearing clays and carbonates that probably formed in an alkaline, groundwater-fed lacustrine setting. This environment strongly contrasts with the acidic, water-limited environments implied by the presence of sulphate deposits that have previously been suggested to form owing to groundwater upwelling. Deposits formed as a result of groundwater upwelling on Mars, such as those in McLaughlin Crater, could preserve critical evidence of a deep biosphere on Mars. We suggest that groundwater upwelling on Mars may have occurred sporadically on local scales, rather than at regional or global scales. © 2013 Macmillan Publishers Limited. All rights reserved.Link_to_subscribed_fulltex

In Appreciation of Our 2019 Peer Reviewers

International audienceScience is at its best when shared widely both within the scientific community and to the broader public. To maintain trust in science while simultaneously maximizing openness, it is important that every paper is carefully vetted. For this we rely on many volunteers, especially our peer reviewers. Their work is key for maintaining the integrity of scientific journals and to ensure the highest standards of scientific rigor. Reviewers verify that the assumptions, the methods, and the inferences made in our papers are sound. Many spend hours going over derivations, analyses, and evaluating the novelty and significance of the submitted manuscript. In 2019, JGR Planets benefited from 901 reviews provided by 584 unique reviewers. On behalf of the entire editorial board of JGR Planets and the entire planetary science community, we want to express here our most heartfelt gratitude to all of you. Thank you

A Spectroscopic Study of Mars-analog Materials with Amorphous Sulfate and Chloride Phases: Implications for Detecting Amorphous Materials on the Martian Surface

The Chemistry and Mineralogy X-ray diffraction (XRD) instrument aboard the Curiosity rover consistently identifies amorphous material at Gale Crater, which is compositionally variable, but often includes elevated sulfur and iron, suggesting that amorphous ferric sulfate (AFS) may be present. Understanding how desiccating ferric sulfate brines affect the spectra of Martian material analogs is necessary for interpreting complex/realistic reaction assemblages. Visible and near-infrared reflectance (VNIR), mid-infrared attenuated total reflectance (MIR, FTIR-ATR), and Raman spectra, along with XRD data are presented for basaltic glass, hematite, gypsum, nontronite, and magnesite, each at three grain sizes (<25, 25–63, and 63–180 μ m), mixed with ferric sulfate (+/−NaCl), deliquesced, then rapidly desiccated in 11% relative humidity or via vacuum. All desiccated products are partially or completely XRD amorphous; crystalline phases include starting materials and trace precipitates, leaving the bulk of the ferric sulfate in the amorphous fraction. Due to considerable spectral masking, AFS detectability is highly dependent on spectroscopic technique and minerals present. This has strong implications for remote and in situ observations of Martian samples that include an amorphous component. AFS is only identifiable in VNIR spectra for magnesite, nontronite, and gypsum samples; hematite and basaltic glass samples appear similar to pure materials. Sulfate features dominate Raman spectra for nontronite and basaltic glass samples; the analog material dominates Raman spectra of hematite and gypsum samples. MIR data are least affected by masking, but basaltic glass is almost undetectable in MIR spectra of those mixtures. NaCl produces similar FTIR-ATR and Raman features, regardless of analog material