Laboratory Curiosity Research Articles

Interactive Mars Image Content-Based Search with Interpretable Machine Learning

The NASA Planetary Data System (PDS) hosts millions of images of planets, moons, and other bodies collected throughout many missions. The ever-expanding nature of data and user engagement demands an interpretable content classification system to support scientific discovery and individual curiosity. In this paper, we leverage a prototype-based architecture to enable users to understand and validate the evidence used by a classifier trained on images from the Mars Science Laboratory (MSL) Curiosity rover mission. In addition to providing explanations, we investigate the diversity and correctness of evidence used by the content-based classifier. The work presented in this paper will be deployed on the PDS Image Atlas, replacing its non-interpretable counterpart.

Evaluating Atmospheric and Surface Drivers for O2 Variations at Gale Crater as Observed by MSL SAM

We explore and evaluate various processes that could drive the variations in the volume mixing ratio (VMR) of atmospheric O2 observed by the quadrupole mass spectrometer (QMS) of the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) Curiosity rover. First reported by Trainer et al. (), these ∼20% variations in the O2 VMR on a seasonal timescale over Mars Years 31–34, in excess of circulation and transport effects driven by the seasonal condensation and sublimation of CO2 at the poles, are significantly shorter than the modeled O2 photochemical lifetime. While there remains significant uncertainty about the various processes we investigated (atmospheric photochemistry, surface oxychlorines and H2O2, dissolution from brines, and airborne dust), the most plausible driver is surface oxychlorines, exchanging O2 with the atmosphere through decomposition by solar ultraviolet and regeneration via O3. A decrease in O3 from increased atmospheric H2O would reduce the removal rate of O2 from the atmosphere to form oxychlorines at the surface. This is consistent with the tentative observation that increases in O2 are associated with increases in water vapor. A lack of correlation with the local surface geology along Curiosity’s traverse within Gale crater, the nonuniqueness of the relevant processes to Gale crater, and the short mixing timescales of the atmosphere all suggest that the O2 variations are a regional, or even global, phenomenon. Nonetheless, further laboratory experiments and modeling are required to accurately scale the laboratory-measured rates to Martian conditions and to fully elucidate the driving mechanisms.

Five Mars Years of Cloud Observations at Gale Crater: Opacities, Variability, and Ice Crystal Habits

We update the record of cloud opacity observations conducted by the Mars Science Laboratory (MSL) Curiosity rover to cover the first five Mars Years (MYs) of the mission (L s = 160° of MY 31 to L s = 160° of MY 36). Over the three MY period that we add to the previously analyzed two MY record, we achieve good diurnal coverage between 07:00 and 17:00 with nearly 1200 new observations. We derive a new scattering phase function for the clouds of the Aphelion Cloud Belt (ACB) using results from the Zenith and Suprahorizon movie data sets. Our phase function is generally smooth and featureless, which is consistent with the overall lack of atmospheric optical phenomena on Mars aside from a single instance of an observed halo. Applying our new phase function to the data, we find that there is very minimal variability in the ACB's opacity, either diurnally, intraseasonally, or interannually, noting that our observations are only sensitive to ice clouds and cannot detect any ice hazes that may be present over Gale. This contrasts with previous results, which observed a 57% difference in the opacity of morning and afternoon clouds in MY 33. The MY 33 results now appear to be an outlier, not replicated at any point during the MSL mission. We conclude that the higher morning opacities in MY 33 were a consequence of an incomplete understanding of the nature of the scattering phase function close to the Sun.

A Mastcam Multispectral Investigation of Rock Variability in Gale Crater, Mars: Implications for Alteration in the Clay‐Sulfate Transition of Mount Sharp

AbstractSince leaving Vera Rubin ridge (VRr), the Mars Science Laboratory Curiosity rover has traversed though the phyllosilicate‐bearing region, Glen Torridon, and the overlying Mg‐sulfate‐bearing strata, with excursions onto the Greenheugh Pediment and Amapari Marker Band. Each of these distinct geologic units were investigated using Curiosity's Mast Camera (Mastcam) multispectral instrument which is sensitive to iron‐bearing phases and some hydrated minerals. We used Mastcam spectra, in combination with chemical data from Chemistry and Mineralogy, Alpha Particle X‐ray Spectrometer, and Chemistry and Camera instruments, to assess the variability of rock spectra and interpret the mineralogy and diagenesis in the clay‐sulfate transition and surrounding regions. We identify four new classes of rock spectra since leaving VRr; two are inherent to dusty and pyroxene‐rich surfaces on the Amapari Marker Band; one is associated with the relatively young, basaltic, Greenheugh Pediment; and the last indicates areas subjected to intense aqueous alteration with an amorphous Fe‐sulfate component, primarily in the clay‐sulfate transition region. To constrain the Mg‐sulfate detection capabilities of Mastcam and aid in the analyses of multispectral data, we also measured the spectral response of mixtures with phyllosilicates, hydrated Mg‐sulfate, and basalt in the laboratory. We find that hydrated Mg‐sulfates are easily masked by other materials, requiring ≥90 wt.% of hydrated Mg‐sulfate to exhibit a hydration signature in Mastcam spectra, which places constraints on the abundance of hydrated Mg‐sulfates along the traverse. Together, these results imply significant compositional changes along the traverse since leaving VRr, and they support the hypothesis of wet‐dry cycles in the clay‐sulfate transition.

Sub‐Diurnal Methane Variations on Mars Driven by Barometric Pumping and Planetary Boundary Layer Evolution

AbstractIn recent years, the Tunable Laser Spectrometer within the Sample Analysis at Mars (TLS‐SAM) instrument on board the Mars Science Laboratory (MSL) Curiosity rover has detected methane variations in the atmosphere at Gale crater. Methane concentrations appear to fluctuate seasonally as well as sub‐diurnally, which is difficult to reconcile with an as‐yet‐unknown transport mechanism delivering the gas from underground to the atmosphere. To potentially explain the fluctuations, we consider barometrically induced transport of methane from an underground source to the surface, modulated by temperature‐dependent adsorption. The subsurface fractured‐rock seepage model is coupled to a simplified 1‐D atmospheric mixing model to provide insights on the pattern of atmospheric methane concentrations in response to transient surface methane emissions, as well as to predict sub‐diurnal variation in methane abundance for the northern summer period, which is a candidate time frame for a MSL Curiosity sampling campaign. Our analysis suggests that there is a lower limit to the subsurface fracture density that can produce the observed methane patterns, below which the atmospheric methane variations would be out of phase with the observations. The best‐performing model scenarios indicate a significant, short‐lived methane pulse just prior to sunrise, the detection of which by TLS‐SAM would be a potential indicator of the contribution of barometric pumping to Mars' atmospheric methane variations.

Comparing Atmospheric Temperature Fluctuations Across Landed Missions

AbstractWe analyze and compare atmospheric temperature data from three landed missions: Mars Science Laboratory (MSL) Curiosity rover, Phoenix lander, and Pathfinder lander. Pathfinder and Phoenix were lander missions that operated for 84 and 151 sols, respectively. MSL Curiosity is a rover that operates on the surface of Mars. It has recorded air temperature for more than five Mars Years (MY). We denoise and detrend temperature data from each mission and use those results to calculate variance in air temperature as a diagnostic for atmospheric variability at the surface. The results show a consistent seasonal pattern in MSL air temperature variance with little interannual variability outside major dust storms. The global dust storm in MY 34 was accompanied by a decrease in temperature variance and a muted response in peak MY 35 variance the following year. Phoenix (68°N, 2 m measurement height) and Pathfinder (19.7°N, 1.1 m measurement height) air temperatures have larger variance than air temperature from environmental data records at the MSL location (5.4°S, 1.6 m measurement height) at its equatorial latitude. Pathfinder variances per sol are larger than those of Phoenix, possibly due to a combination of Pathfinder's lower albedo surface and lower latitude. This occurs despite the Pathfinder location's higher thermal inertia, which would act to decrease noontime variance relative to a lower thermal inertia surface. Comparison of MSL temperature variance to pressure drops related to convective vortex activity shows consistent seasonal patterns; however, pressure drops tend to increase with increasing rover elevation, while variance remains consistent.

Evolution of a Lake Margin Recorded in the Sutton Island Member of the Murray Formation, Gale Crater, Mars

AbstractThis study uses data from the Mars Science Laboratory Curiosity rover to document the facies of the Sutton Island member of the Murray formation, interpret paleoenvironments, and establish key stratigraphic transitions at Gale crater. Two facies associations were identified: Facies Association 1 (FA1) and Facies Association 2 (FA2). Individual facies in FA1 include planar‐laminated mudstone with minor intervals of planar sandstone, ripple cross‐laminated sandstone, cross‐stratified sandstone, and alternating laminated sandstone and mudstone. Meter‐thick packages of planar‐laminated mudstone in FA1 are interpreted to represent deposition in low‐energy ponded environments along the lake margin. Straight‐ and curve‐crested ripple cross‐laminated facies are interpreted to represent current‐influenced deposition. Cross‐stratified sandstone facies consist of dm‐thick sets that represent deposition in distal channels. Intercalated mm‐scale mudstone and sandstone laminae represent waning flow conditions and possible channel abandonment. Facies in FA1 collectively represent deposition in a distal delta plain. FA2 is comprised of planar‐laminated mudstone with minor sandstone and is interpreted to represent deposition in a lacustrine‐basin setting by suspension settling linked to density flows. FA1 transitions upward into FA2, defining a rapid transgression substantial enough to facilitate the deposition of distal lake facies above delta plain facies. The abrupt transition from FA2 back to FA1 deltaic deposits is suggestive of forced regression. Facies in FA1 and FA2 are consistent with the prevalence of aqueous environments recorded in other Murray formation members and extend our understanding of the dynamic sedimentary processes that characterized ancient lacustrine systems at Gale crater.

Aeolian bedrock ridges in Gale crater, Mars

Fields of parallel, regularly-spaced, bedrock ridges observed on Mars and rarely on Earth have been interpreted as aeolian surface features oriented perpendicular to a formative wind. The exact formation process for these ridges, however, including the role of aeolian erosion versus deposition, continues to be debated. We identified forty fields of bedrock ridges on and within the sedimentary strata of Gale crater's central mound, Aeolis Mons. To better constrain the development of these landforms and the winds responsible for their formation, we characterized ridge morphology, orientation, geographic distribution, stratigraphic relationships, and interactions with other aeolian landforms. The study area of Aeolis Mons was chosen to leverage the extensive high-resolution image coverage from orbit, as well as to build upon the detailed stratigraphy compiled from in situ exploration with the Mars Science Laboratory Curiosity rover. Using the orientation of the ridges, we present a wind vector map of Aeolis Mons. The orientation of bedrock ridges in the Mound Skirting Unit, which unconformably drapes Aeolis Mons, suggests the average wind direction in Gale crater may have remained consistent since that unit was emplaced (∼3.8–3.1 Ga). This study explores the implications of these ridges for the history of wind, deposition, and erosion in Gale crater.

Dust Lifting Observations With the Mars Science Laboratory Navigation Cameras

AbstractMartian dust lifting is believed to occur through two primary mechanisms: dust devils and wind stress forced dust lifting. Gale Crater's varied terrain and meteorology provide a unique in situ perspective on Martian dust lifting, with the Mars Science Laboratory Curiosity rover passing through both conditions and locations detrimental to dust lifting (e.g., the crater floor) and those with active sand motion and frequent dust lifting (e.g., the Bagnold Dunes). Between Ls = 248° in Mars Year 33 and Ls = 51° in Mars Year 37, over ∼3.5 Mars years and 2,300 sols, the rover's Navigation Cameras took 1,260 dedicated image sequences to search for dust lifting. Approximately 42.7% of all sequences, and 9.5% of the total images have shown active dust lifting, both dust devils and linear/straight‐line wind stress dust lifting. 79% of dust lifting events are classified as dust devils, while ∼16% are linear wind stress dust lifting and the remainder are of an indeterminate type. We analyze this large catalog of dust lifting events to provide ground truth on theoretical and model expectations of dust lifting and show that dust lifting in Gale Crater occurs throughout the Martian year, is strongly peaked in frequency near solar noon (even after accounting for observational biases), and that dust lifting shows an affinity for sand‐covered surfaces which highlights the importance of saltating sand grains for Martian dust lifting in both dust devils and wind stress forced lifting.

The Mars Science Laboratory record of optical depth measurements via solar imaging

The Mars Science Laboratory Curiosity rover has monitored the Martian environment in Gale crater since landing in 2012. This study reports the record of optical depth derived from visible and near-infrared images of the Sun. Aerosol optical depth, which is mostly due to dust but also includes ice, dominates the record, with gas optical depth too small to measure. The optical depth record includes the effects of regional dust storms and one planet-encircling dust event, showing the expected peaks during southern spring and summer and relatively lower and more stable optical depth in fall and winter. The measurements show that there is a seasonally varying diurnal change in dust load, with the optical depth peaking in the morning during southern spring and summer, correlated with thermotidal pressure changes. However, there was no systematic diurnal change during autumn and winter, except after one regional storm. There were indications that the dust was relatively enhanced at high altitudes during high-optical-depth periods and that high-altitude ice was significant during winter. The observations did not provide much information about particle size or composition, but they were consistent with a smaller particle size after aphelion (in southern winter). No scattering halos were seen in associated sky images, even when there was visual evidence of ice hazes or clouds, which suggests small or amorphous ice particles. Unexpectedly, the measurement campaign revealed that the cameras collected saltating sand in their sunshades 1.97 m above the surface. As a result, the measurement strategy had to be adjusted to avoid high-elevation imaging to avoid sand covering the optics.

Peter John Lawrenson. 12 March 1933—27 October 2017

Born in Prescot, Lancashire, Peter Lawrenson rose from relatively humble origins to become a leading figure in the world of electrical motors and generators—first as an academic and latterly as a businessman. Noteworthy research throughout the 1960s quickly earned him a personal chair at the University of Leeds, and for a number of years he was head of department at the university's School of Electrical & Electronic Engineering. He is particularly remembered for pioneering the application of numerical methods to electromagnetic field problems, and for promoting and commercializing the switched reluctance motor, which—via the business, Switched Reluctance Drives Ltd, that he co-founded with research colleagues—was transformed from a laboratory curiosity to a commercially viable and highly efficient alternative to conventional electrical machines. A leading figure in the Institution of Electrical Engineers (IEE, latterly the IET), he also served with distinction as IEE president in 1992.

Tris(2,2'-bipyridyl)ruthenium (II) complex as a universal reagent for the fabrication of heterogeneous electrochemiluminescence platforms and its recent analytical applications.

In recent years, electrochemiluminescence (ECL) has received enormous attention and has emerged as one of the most successful tools in the field of analytical science. Compared with homogeneous ECL, the heterogeneous (or solid-state) ECL has enhanced the rate of the electron transfer kinetics and offers rapid response time, which is highly beneficial in point-of-care and clinical applications. In ECL, the luminophore is the key element, which dictates the overall performance of the ECL-based sensors in various analytical applications. Tris(2,2'-bipyridyl)ruthenium (II) complex, Ru(bpy)32+, is a coordination compound, which is the gold-standard luminophore in ECL. It has played a key role in translating ECL from a "laboratory curiosity" to a commercial analytical instrument for diagnosis. The aim of the present review is to provide the principles of ECL and classical reaction mechanisms-particularly involving the heterogeneous Ru(bpy)32+/co-reactant ECL systems, as well as the fabrication methods and its importance over solution-phase Ru(bpy)32+ ECL. Then, we discussed the emerging technology in solid-state Ru(bpy)32+ ECL-sensing platforms and their recent potential analytical applications such as in immunoassay sensors, DNA sensors, aptasensors, bio-imaging, latent fingerprint detection, point-of-care testing, and detection of non-biomolecules. Finally, we also briefly cover the recent advances in solid-state Ru(bpy)32+ ECL coupled with the hyphenated techniques.

Driving up the quality of metal organic chemical vapor deposition-grown epitaxial wafers for highly innovative photonic applications

Quantum cascade lasers (QCL) and extended InGaAs photodetectors (ex-PDs) (operating in regime 1.9–2.6 µm wavelength) are very attractive materials for use in sophisticated photonics and microelectronics such as optical recording, scanners, laser spectroscopy, thermal or gas sensing. Once a laboratory curiosity, QCLs and ex-PDs are now becoming commercially available products, shaping exciting applications. In this work, we present the intricacies and challenges of the development and industrial production of Metal Organic Chemical Vapor Deposition (MOCVD)-grown QCL and ex-PD structures as well as demonstrate their viability for large-scale manufacturing.Different types of epitaxial structures were grown using a multi-wafer production MOCVD system, in 12 × 3″ wafer configuration per growth run. Structural and electrical properties of epitaxial layers were carefully examined.MOCVD growing of QCL and ex-PD structures is a very demanding process. MOCVD production reactor enables development of highly complicated chemical reactions, however, as gas residence is much longer than in small R&D systems, the hetero-interfaces of InGaAs/InAlAs are inevitably graded, which negatively impacts optical and electrical parameters of QCL devices. In addition, QCL structure requires the exact layer thickness as well as absolute precision and repeatability when developing strained InAlAs and InGaAs epi‑layers. In the case of ex-PDs fabrication, the crucial thing is to develop a specially designed and graded buffer layer, and to avoid numerous misfit defects and anomalies in dark current. We obtained high crystallographic quality and repeatability of the epi‑layers, which resulted in QCL high-performance continuous-wave operation and fabrication of ex-PDs with low dark current density (less than 1 × 10−4 A/cm2 at -100 mV/room temperature (RT)) achieving results consistent with Rule07 and higher quantum efficiency.

Sensitive and accurate determination of nitrogen in simulated Martian soil and environment with LIBS spectrum fusion and regression based on neural network

Nitrogen is a key element necessary for the emergence and development of life. It is one of the elements targeted by the landed missions on Mars in accordance with their scientific goal of investigation of habitability and search for traces of life. A gas chromatography mass spectrometer (GCMS) instrument on board the Mars Science Laboratory Curiosity rover has revealed the existence of oxidized nitrogen-bearing compounds on Martian surface with an equivalent nitrogen concentration up to 0.01 wt%. Although the detection with laser-induced breakdown spectroscopy (LIBS) also on board the Curiosity rover is desirable, the current performance of LIBS for nitrogen analysis does not show the capacity in terms of limit of detection (LOD) and accuracy. Research on a suitable method should therefore be first engaged in laboratory in order to guide further improvements of LIBS instrument on board Mars rover, as well as the data treatment method. Beyond the sensitivity issue, matrix effect also affects LIBS determination of nitrogen, especially due to its various chemical speciation in geological materials. Method research should answer thus double requirements of improving the sensitivity and reinforcing the robustness with respect to different nitrogen-bearing compounds. An experimental configuration of double detections with a narrow bandwidth Czerny-Tuner (CT) spectrometer and a broad bandwidth Echelle spectrometer, was implemented in this work, in such way that the first ensured a sensitive detection of emission lines from nitrogen and the second complemented with those from major elements in the sample. The fusion of the simultaneously acquired spectra took into account the emission characteristics of the both two types of elements, necessary for an effective and robust multivariate regression based on a neural network. In addition, for a better treatment of different chemical speciation of nitrogen in samples, generalized spectrum was used for training of regression models, after an unsupervised clustering having assigned a type label to each training spectrum. The trained model was tested by collections of independent test samples, resulting in a limit of detection (LOD) of 0.18 wt%, and a root mean square error of prediction (RMSEP) of 0.041 wt%, representing a step forward to nitrogen detection using LIBS on Mars.

Enantioselective Strategies for The Synthesis of N−N Atropisomers

AbstractAxially chiral compounds have been always considered a laboratory curiosity with rare prospects of being applied in asymmetric synthesis. Things have changed very quickly in the last twenty years when it was understood the important role and the enormous impact that these compounds have in medicinal, biological and material chemistry. The asymmetric synthesis of atropisomers became a rapidly expanding field and recent reports on the development of N−N atropisomers strongly prove how this research field is a hot topic open to new challenges and frontiers of asymmetric synthesis. This review focuses on the recent advances in the enantioselective synthesis of N−N atropisomers highlighting the strategies and breakthroughs to obtain this novel and stimulating atropisomeric framework.

Enantioselective Strategies for The Synthesis of N-N Atropisomers.

Axially chiral compounds have been always considered a laboratory curiosity with rare prospects of being applied in asymmetric synthesis. Things have changed very quickly in the last twenty years when it was understood the important role and the enormous impact that these compounds have in medicinal, biological and material chemistry. The asymmetric synthesis of atropisomers became a rapidly expanding field and recent reports on the development of N-N atropisomers strongly prove how this research field is a hot topic open to new challenges and frontiers of asymmetric synthesis. This review focuses on the recent advances in the enantioselective synthesis of N-N atropisomers highlighting the strategies and breakthroughs to obtain this novel and stimulating atropisomeric framework.

Attentional development can help us understand the inattentional blindness effect in visual search

IntroductionInattentional Blindness (IB) is the failure to notice an unexpected, usually salient stimulus while immersed in a different, often demanding attentional task. More than just a laboratory curiosity, IB is an important phenomenon to understand because it may be related to real-world errors such as missed “incidental findings” in medical image or security searches. Interest in individual differences in susceptibility to IB has produced a number of studies showing inconclusive results.MethodsHere, we tested IB in a sample of 277 participants, 4-25 years old performing a visual search task. On two critical trials, an unexpected letter and an unexpected word were presented among photorealistic objects.ResultsThere was a clear age effect with younger individuals showing higher IB levels. IB correlated with attentional control in visual search and with Continuous Performance Test-CPT for d-prime, response times and attentional shifting measures. These effects disappeared if age was controlled. There were no general effects of intelligence (IQ; RIST) or gender. Younger observers showed a negative correlation of IB for the word with the verbal components of the RIST IQ-proxy (no effect for the letter).DiscussionThese results support a relationship between IB and cognitive-developmental changes, showing that maturation of attention and executive processes can help us understand the intriguing phenomenon of (sometimes) missing what is in front of our eyes.

Jack Dwayne Farmer April 18, 1947-February 22, 2023.

AstrobiologyAhead of Print TributeFree AccessJack Dwayne Farmer April 18, 1947–February 22, 2023David J. Des Marais, Maria C. Farmer, Ariel D. Anbar, Jonathan Zaloumis, Svetlana Shkolyar, Charlene Estrada, and Sherry L. CadyDavid J. Des MaraisSearch for more papers by this author, Maria C. FarmerSearch for more papers by this author, Ariel D. AnbarSearch for more papers by this author, Jonathan ZaloumisSearch for more papers by this author, Svetlana ShkolyarSearch for more papers by this author, Charlene EstradaSearch for more papers by this author, and Sherry L. CadySearch for more papers by this authorPublished Online:5 May 2023https://doi.org/10.1089/ast.2023.0044AboutSectionsPDF/EPUB Permissions & CitationsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail Jack Dwayne Farmer. Image by J. Shostak, SETI InstituteJack Dwayne Farmer was an exceptional scholar, field geologist, teacher, mentor, and key contributor to NASA's flight missions and programs. He was also an exemplary friend and advocate for so many people from all walks of life. He will be deeply missed.Early in his career, Jack was a lecturer and collections curator at University of California (UC), Davis and its Bodega Laboratory, a senior petroleum geologist at Exxon, an adjunct professor at UCLA, and a visiting professor at California State University, Long Beach (Fig. 1). Jack later became a world leader in the burgeoning field of astrobiology (an expansion of NASA's earlier Exobiology program). His never-ending curiosity about the roles that microbes play in chemical sedimentary systems took him to field sites on nearly every continent. He centered his research on biomineralization processes and the various ways in which life modifies sedimentary fabrics in hydrothermal systems, evaporative lakes, and arid soils. Along with the students and colleagues he mentored, Jack examined the processes that contribute to the capture and preservation of biosignatures over a broad range of environmental conditions, including the influences of biology on diagenesis. His broad range of experiences enabled him to contribute novel insights into the early record of life on Earth and champion an enduring framework to search for a record of past and present life on Mars.FIG. 1. Jack's early career days. (Left) Preparing for an ocean dive at Bodega Research Laboratory. (Right) On Exxon's offshore platform Harmony. Photographers unknown; images provided by M.C. Farmer.While at NASA's Ames Research Center in the 1990s, Jack pursued field studies in environments on Earth that resembled those on early Mars. He investigated microbial fossilization and the biosedimentology of extreme environments, microbial processes in early diagenesis, the morphogenesis of modern and ancient microbial stromatolites, and the roles that metazoan grazers play in stromatolite morphogenesis. Jack's studies of microbial mat ecosystems at Guerrero Negro, Baja California Sur, Mexico, provided an important environmental context for the many biogeochemical investigations conducted later at that site. He studied thermal spring microbial communities and mineral deposits at Yellowstone National Park and other localities in the western United States (Fig. 2) and documented the morphological and geochemical features in the sedimentary facies of acid and alkaline thermal springs. He catalogued an array of features in a Devonian-age thermal spring deposit that corresponded closely to those of modern hot springs, and he outlined in detail a systematic paleontological approach to characterizing ancient thermal spring deposits.FIG. 2. Jack during his NASA research scientist days in Yellowstone National Park, USA. (Left) Sampling a hot spring in Yellowstone National Park, USA. Image by Michael Milstein. (Right) Mammoth Hot Springs, Yellowstone (left to right): Baruch Blumberg (NAI Director), Catherine Tsairides (Lockheed-Martin), Linda Young (NPS), Jack Farmer (ASU), Dave Ward (Montana State University), Dave Des Marais (NASA), and Nancy Hinman (University of Montana). Image by D.J. Des Marais.Jack also became extensively involved with NASA mission planning during the 1990s. He assumed a key role in planning Mars exploration when it faced daunting challenges and performed landing site studies to support the exploration for martian life (Fig. 3). Importantly, Jack advocated that any search for evidence of past or present life must occur within the context of characterizing past environments, including their climates, sedimentary processes, and potential for preserving a fossil record. He coined the term “exopaleontology” and championed many of the principles that the Mars Exploration Program continues to incorporate to this day.FIG. 3. Jack with a Mars Planetary Protection document. Image by M.C. Farmer.After joining Arizona State University (ASU) in 1998, Jack continued his research in geobiology and involved his students in projects relevant to the geological and astrobiological exploration of Mars. He investigated the microbial biosedimentology of extreme environments (e.g., hydrothermal, hypersaline, arid, polar, deep sea), early biosphere development, the evolution of Precambrian benthos, and the origins of multicellular life. He contributed to developing scientific instrumentation for flight missions and Mars analog environment studies. One example is a multispectral microscopic imager, which he helped develop and deploy in the field. He received the NASA Group Achievement Award for the In Situ Lunar Surface Operations and in situ Resource Utilization (ILSO/ISRU) Field Test on Mauna Kea, Hawaiʻi.Jack participated directly in Mars landed missions (Fig. 4). He served as a Long-Term Planning Lead on the MER Science Operations Working Group for the Spirit rover and helped document features formed by an ancient hydrothermal system in the Columbia Hills region of Gusev Crater. He helped interpret the significance of opaline silica observed by Spirit, facilitating one of the first discoveries of an ancient habitable environment on Mars. He also was a member of the CheMin instrument team of the Mars Science Laboratory (Curiosity rover) mission. Identifications of minerals by this X-ray diffraction instrument have characterized past ancient habitable environments within Gale Crater.FIG. 4. Jack's involvement in NASA missions. (Left) 2002 FIDO rover trials at JPL (left to right): Jack Farmer (ASU), Larry Soderblom (USGS), John Grotzinger (MIT), and Andrew Knoll (Harvard). (Right) Launch of the Curiosity rover, 2011, Kennedy Space Center (left to right): David Blake (NASA, Ames), David Vaniman (Los Alamos National Laboratory), and Jack Farmer (ASU). Images by D.J. Des Marais.In parallel with his research and teaching, Jack provided extensive service to his university, the broader scientific community, and the public. At ASU, he became Director of the ASU Astrobiology Program and Principal Investigator of one of the founding teams in NASA's Astrobiology Institute (NAI). He was a member of NASA's Space Science Advisory Committee and a Chair of the Mars Exploration Program Analysis Group (MEPAG), which performs studies and sponsors an active forum with the Mars science community. Jack contributed to the revision of NASA's 2004 Astrobiology Roadmap and substantially influenced the astrobiology strategy for Mars exploration. He also served as an officer for the Geological Society of America (GSA) and received the GSA Geobiology and Geomicrobiology Division Award for outstanding contributions to the fields of geobiology and geomicrobiology.Jack was an exemplary instructor and mentor at UC Davis, UCLA, and ASU (Fig. 5). He taught courses in paleontology, sedimentology, oceanography, planetary science, mineralogy, petrology, astrobiology, and physical and historical geology. He innovated several teaching techniques, particularly during the recent pandemic. For example, he created 3-D scans of geologic specimens that were employed extensively during remote instruction. He was beloved by his students. At ASU's School of Earth and Space Exploration (SESE), he was highly sought out by undergraduates for his generous dedication to answering science questions and for providing professional career advice. He was a highly conscientious and caring graduate student mentor.FIG. 5. Jack with graduate students Marisol Juarez Rivera, Svetlana Shkolyar, postdoc Charlene Estrada, and undergraduate Nicky Marin. Image provided by M.C. Farmer.Jack was dedicated to informal education. He engaged the public through numerous articles, lectures, and TV and radio interviews. As “Dr. Rock,” he became an institution at SESE's annual “Earth and Space Exploration Day” (Fig. 6), introducing countless elementary-age children to the wonders of geology. He was an instructor for the Mars Education Program at ASU, particularly in activities that offered science experiences to teachers and students.FIG. 6. Jack sharing his geological expertise. (Left) “Dr Rock” identifying rocks at SESE's Earth and Space Exploration Day. Image by M.C. Farmer. (Right) Jack leading a field trip at Steamboat Springs, Nevada. Image by D.J. Des Marais.Jack was particularly active in outreach to Native American communities, being himself of Cherokee and Chickasaw ancestry. He co-founded the Northern California Professional Chapter of the American Indian Science and Engineering Society (AISES, Fig. 7). He participated extensively in several professional Native American organizations, including the Society for Advancement of Chicanos/Hispanics and Native Americans in Science (SACNAS), for which he was honored.FIG. 7. Jack thriving with his own and his greater family. (Left) Bethany, Jack, and Maria Farmer at the 2021 AISES National Conference. Image by M.C. Farmer. (Center) Jack giving the keynote talk at the 2014 SACNAS National Conference. (Right) Jack being honored for his service with a Pendleton blanket. Image by SACNAS.Jack was an avid guitarist and singer, much to the delight of those fortunate enough to share a campfire with him after a day in the field.For his career achievements, Jack was elected Fellow of the Geological Society of America. He received the Erasmus S. Haworth Distinguished Alumnus Award for academic achievements in research, teaching, and service given by the Department of Geology, University of Kansas. Chico State awarded him a distinguished alumni award.Through it all, and perhaps most fundamentally, Jack was a generous and patient teacher. He loved to share his knowledge, especially in the field. He never talked down to anyone, as he was that rare scholar who could meet you where you were, whether novice or peer, wanting nothing more than to enlighten and inspire. It was a key secret to much of his success.Jack Farmer's exceptional legacy will endure among his family, friends, colleagues, students, and in various disciplines of science, most importantly the field of astrobiology (Fig. 8). His favorite quote, below, characterizes his wishes for the fields of science that he loved.FIG. 8. Jack at an outcrop in the Trendall Reserve, Pilbara Craton, Western Australia. Image by G. Bruce.There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved. (Charles Darwin, On the Origin of Species)—David J. Des Marais, Maria C. Farmer, Ariel D. Anbar, Jonathan Zaloumis, Svetlana Shkolyar, Charlene Estrada, and Sherry L. CadyFiguresReferencesRelatedDetails Volume 0Issue 0 InformationCopyright 2023, Mary Ann Liebert, Inc., publishersTo cite this article:David J. Des Marais, Maria C. Farmer, Ariel D. Anbar, Jonathan Zaloumis, Svetlana Shkolyar, Charlene Estrada, and Sherry L. Cady.Jack Dwayne Farmer April 18, 1947–February 22, 2023.Astrobiology.ahead of printhttp://doi.org/10.1089/ast.2023.0044Online Ahead of Print:May 5, 2023PDF download

Boron adsorption in clay minerals: Implications for martian groundwater chemistry and boron on Mars

Boron has been detected on Mars in calcium-sulfate veins found within clay mineral rich rocks on Mars by the Mars Science Laboratory (MSL) Curiosity rover using Laser Induced Breakdown Spectroscopy (LIBS) analysis. Borates play a vital role in stabilizing ribose on Earth and has been suggested as a key requirement for life. Borate ions readily adsorb to phyllosilicate clay minerals. The discovery of boron on Mars in proximity to phyllosilicate-bearing bedrock may have strong implications for potential past prebiotic conditions on Mars. In this study we generated a suite of clay minerals with adsorbed borate, including both typical terrestrial clay minerals (montmorillonite) and Mars-analog clay minerals (nontronite, saponite, griffithite), to understand controls on borate adsorption and to analyze with LIBS to compare with MSL data. Clay minerals were subjected to mineralogical and chemical analysis before and after adsorption. Adsorption analysis revealed that the Mars analog clay minerals adsorbed less boron than terrestrial counterparts, but within comparable amounts to those detected on Mars and in meteorites. Post-adsorption analysis by X-ray diffraction (XRD) revealed slight changes in the interlayer spacing of many of the clay minerals. Based on the adsorption analysis of the Mars-analog clay minerals, phyllosilicate-bearing bedrock in Gale crater may contain up to 90-110 ppm B. A series of borate-enriched samples were created for analysis of LIBS spectra from ChemCam on the Curiosity rover and SuperCam on the Perseverance Rover. The results of this study may provide insight into martian groundwater geochemistry processes and the mobility of a key molecule connected with life.

The Zenith‐Angle Dependence of the Downward Radiation Dose Rate on the Martian Surface: Modeling Versus MSL/RAD Measurement

AbstractThe Radiation Assessment Detector (RAD) on board the Mars Science Laboratory's Curiosity rover has been monitoring the surface radiation environment on Mars for just over 10 years. It has been found by Wimmer‐Schweingruber et al. (2015, https://doi.org/10.1002/2015gl066664) that within the narrow view cone of RAD, the directionality of the radiation field is close to but not completely isotropic. In order to better understand the directionality of the surface radiation over a wide range of zenith angles (θ), we perform a three‐dimensional Geant4 Monte Carlo simulation to derive the θ‐dependence of the surface dose rate. The results show that galactic cosmic ray protons, coming in at θ ∼ 74° make the greatest contribution to the surface dose. For helium ions, this angle is at around 46°. This is a consequence of the increasing column depth at larger zenith angles and the complex interplay of the destruction of primary and the creation of secondary particles as the primary cosmic ray interacts with the Martian atmosphere. We also compared the simulated results with the RAD measurements and found a reasonable agreement. Our results are important for future human exploration of Mars, for instance, to estimate the effectiveness of radiation shielding of a given geometry or for optimizing the radiation shielding design of a Martian habitat.