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NASA NTRS2007

Iapetus' Geophysics: Rotation Rate, Shape, and Equatorial Ridge

Iapetus has preserved evidence that constrains the modeling of its geophysical history from the time of its accretion until now. The evidence is (a) its present 79.33-day rotation or spin rate, (b) its shape that corresponds to the equilibrium figure for a hydrostatic body rotating with a period of approximately 16 h, and (c) its high, equatorial ridge, which is unique in the Solar System. This paper reports the results of an investigation into the coupling between Iapetus' thermal and orbital evolution for a wide range of conditions including the spatial distributions with time of composition, porosity, short-lived radioactive isotopes (SLRI), and temperature. The thermal model uses conductive heat transfer with temperature-dependent conductivity. Only models with a thick lithosphere and an interior viscosity in the range of about the water ice melting point can explain the observed shape. Short-lived radioactive isotopes provide the heat needed to decrease porosity in Iapetus? early history. This increases thermal conductivity and allows the development of the strong lithosphere that is required to preserve the 16-h rotational shape and the high vertical relief of the topography. Long-lived radioactive isotopes and SLRI raise internal temperatures high enough that significant tidal dissipation can start, and despin Iapetus to synchronous rotation. This occurred several hundred million years after Iapetus formed. The models also constrain the time when Iapetus formed because the successful models are critically dependent upon having just the right amount of heat added by SLRI decay in this early period. The amount of heat available from short-lived radioactivity is not a free parameter but is fixed by the time when Iapetus accreted, by the canonical concentration of Al-26, and, to a lesser extent, by the concentration of Fe-60. The needed amount of heat is available only if Iapetus accreted between 2.5 and 5.0Myr after the formation of the calcium aluminum inclusions as found in meteorites. Models with these features allow us to explain Iapetus? present synchronous rotation, its fossil 16-h shape, and the context within which the equatorial ridge arose.

geophysics↗

NASA NTRS2012

The Lunar Regolith as a Recorder of Cosmic History

The Moon can be considered a giant tape recorder containing the history of the solar system and Universe. The lunar regolith (soil) has recorded the early history of the Moon, Earth, the solar system and Universe. A major goal of future lunar exploration should be to find and play back existing fragments of that tape . By reading the lunar tape, we can uncover a record of planetary bombardment, as well as solar and stellar variability. The Moon can tell us much about our place in the Universe. The lunar regolith has likely recorded the original meteoritic bombardment of Earth and Moon, a violent cataclysm that may have peaked around 4 Gyr, and the less intense bombardment occurring since that time. This impact history is preserved on the Moon as regolith layers, ejecta layers, impact melt rocks, and ancient impact breccias. The impact history of the Earth and Moon possibly had profound effects on the origin and development of life. Decrease in meteor bombardment allowed life to develop on Earth. Life may have developed first on another body, such as Mars, then arrived via meteorite on Earth. The solar system may have experienced bursts of severe radiation from the Sun, other stars, or from unknown sources. The lunar regolith has recorded this radiation history in the form of implanted solar wind, solar flare materials and radiation damage. Lunar soil can be found sandwiched between layers of basalt or pyroclastic deposits. This filling constitutes a buried time capsule that is likely to contain well-preserved ancient regolith. Study of such samples will show us how the solar system has evolved and changed over time. The lunar tape recorder can provide detailed information on specific portions of solar and stellar variability. Data from the Moon also offers clues as to whether so-called fundamental constants have changed over time.

Cooper, Bonnie↗

NASA NTRS1994

Rates of Earth degassing

The degassing of the Earth during accretion is constrained by Pu-U-I-Xe systematics. Degassing was much more efficient during the first 100-200 Ma than subsequently, and it was more complete for Xe than for the lighter gases. More than 90 percent of the degassed Xe escaped from the atmosphere during this period. The combination of fractional degassing of melts and rare gas escape from the atmosphere is able to explain the deficit of terrestrial Xe as a simple consequence of this early degassing history. By the time Xe was quantitatively retained in the atmosphere, the abundances of Kr and the lighter gases in the Earth's interior were similar to or higher than the present-day atmospheric abundances. Subsequent transfer of these lighter rare gases into the atmosphere requires a high rate of post-accretion degassing and melt production. Considerations of Pu-U-Xe systematics suggest that relatively rapid post-accretion degassing was continued to ca. 4.1-4.2 Ga. The present-day degassing history of the Earth is investigated through consideration of rare gas isotope abundances. Although the Earth is a highly degassed body, depleted in rare gases by many orders of magnitude relative to their solar abundances, it is at the present-day losing primordial rare gases which were trapped at the time of accretion.

Onions, R. K.↗

NASA NTRS1984

Maintenance of time and frequency in the Jet Propulsion Laboratory's Deep Space Network using the Global Positioning System

The Deep Space Network (DSN), managed by the Jet Propulsion Laboratory for NASA, must maintain time and frequency within specified limits in order to accurately track the spacecraft engaged in deep space exploration. Various methods are used to coordinate the clocks among the three tracking complexes. These methods include Loran-C, TV Line 10, Very Long Baseline Interferometry (VLBI), and the Global Positioning System (GPS). Calculations are made to obtain frequency offsets and Allan variances. These data are analyzed and used to monitor the performance of the hydrogen masers that provide the reference frequencies for the DSN Frequency and Timing System (DFT). Areas of discussion are: (1) a brief history of the GPS timing receivers in the DSN, (2) a description of the data and information flow, (3) data on the performance of the DSN master clocks and GPS measurement system, and (4) a description of hydrogen maser frequency steering using these data.

Clements, P. A.↗

NASA NTRSDate not supplied

Changes in Alertness and Performance Over Time During Long-Haul Flying Across Multiple Time Zones

BACKGROUND: Long-haul pilots experience high levels of fatigue and circadian disruptions due to long work hours and flying over multiple time zones. The aim of this study was to describe changes in alertness and performance among flight crews during long-haul flights crossing multiple time zones. METHODS: All pilots flying long-haul operations from a single airline were eligible to participate. All participants collected data for ~2 weeks of their normal work schedule within airline operations, with at least two long-haul rotations, including rest days and layovers. Participants wore an Actiwach throughout the entire study period and completed a sleep diary (at bedtime, upon waking up and after each nap). Each participant completed a 5-min Psychomotor Vigilance Task (PVT) and a Karolinska Sleepiness Scale (KSS) pre-flight, on top-of-descent (TOD; inflight) and at the end of each flight (post-flight). Response speed (1/RT x 1000), lapses (RT > 500 ms), and alertness were assessed over time pre-flight, TOD, post-flight, using mixed-effects models with participant as a random factor. Linear models were assumed for response speed and alertness, while a negative binomial distribution was specified for lapses due to overdispersion. RESULTS: Forty-four long-haul pilots participated in the study (5 female; mean age 44.25 ± 10.06 yrs; mean flight hours 9834.3; ± 5334.1 hrs). Lapses increased post-flight relative to pre-flight (F(2, 665) = 3.67, p < 0.05). There was a main effect of response speed (F(2, 665) = 21.45, p < 0.001) with slower speed inflight and postflight compared to preflight (p < 0.001). The KSS increased over time from M = 4.02 (± 1.35) preflight to M = 5.15 (± 1.58) inflight, to M = 6.7 (± 1.51) postflight (F(2, 701) = 182.63, p < 0.001). DISCUSSION: Our preliminary analyses showed that both performance and subjective alertness worsened from the beginning to the end of a flight. Additional analyses will be conducted to investigate the changes in alertness and performance by direction of travel, sleep history, and flight timing and duration.

long-haul↗

DOE OSTI2023

Conference Report on the 7th International Symposium on Liquid metals Applications for fusion (ISLA-7)

Supported by the world magnetic fusion research community, a series of International Symposia on Liquid metals Applications for fusion (ISLA) have been held biannually since 2010. The 7th edition (ISLA-7) was held for the period from 12 December through 16 December 2022, at Chubu University located in Kasugai, Aichi, Japan. For the first time in the history of this series of symposia, ISLA-7 was held in a hybrid fashion, due to the COVID-19 situation. The total number of the participants was 60, 34 out of whom attended the symposium in person, and the rest participated online. As to the presentation statistics, 29 papers were presented in person, whereas 21 presentations were delivered online but real-time by the presenters in China, Spain, the UK, and the USA. Both of the presentations delivered in person and online were recorded, and the video has been shared by all participants. These participants represent 11 countries: China, Czech, Italy, Japan, Latvia, Netherlands, Russia, Thailand, the UK, and the USA. All these numbers are among the largest in this series of symposia. Covered by these presentations are; in session-2, program overviews and liquid metal research review; in session-3, liquid metal flows, and MHD issues; in session-4, liquid metal facilities; in sessions-5 and 6, liquid metal experiments and modeling; in session-7, divertor physics and heat flux mitigation; in session-8, plasma and liquid metals interactions; in session-9 liquid metal plasma-facing components, erosion, and wettability. In addition, there were an opening session whereby several opening addresses were delivered and also a closing session where all technical session summaries were presented by the respective session chairs.

divertor↗

NASA NTRS2007

Coupled Nd-142, Nd-143 and Hf-176 Isotopic Data from 3.6-3.9 Ga Rocks: New Constraints on the Timing of Early Terrestrial Chemical Reservoirs

Increasingly precise data from a range of isotopic decay schemes, including now extinct parent isotopes, from samples of the Earth, Mars, Moon and meteorites are rapidly revising our views of early planetary differentiation. Recognising Nd-142 isotopic variations in terrestrial rocks (which can only arise from events occurring during the lifetime of now extinct Sm-146 [t(sub 1/2)=103 myr]) has been an on-going quest starting with Harper and Jacobsen. The significance of Nd-142 variations is that they unequivocally reflect early silicate differentiation processes operating in the first 500 myr of Earth history, the key time period between accretion and the beginning of the rock record. The recent establishment of the existence of Nd-142 variations in ancient Earth materials has opened a new range of questions including, how widespread is the evidence of early differentiation, how do Nd-142 compositions vary with time, rock type and geographic setting, and, combined with other types of isotopic and geochemical data, what can Nd-142 isotopic variations reveal about the timing and mechanisms of early terrestrial differentiation? To explore these questions we are determining high precision Nd-142, Nd-143 and Hf-176 isotopic compositions from the oldest well preserved (3.63- 3.87 Ga), rock suites from the extensive early Archean terranes of southwest Greenland and western Australia.

Bennett, Vickie C.↗

DOE OSTI2014

Leisure time activities related to carcinogen exposure and lung cancer risk in never smokers. A case-control study

We aim to assess the relationship between leisure time activities related to exposure to carcinogenic substances and lung cancer risk in a hospital-based case-control study performed in never smokers. We included never smoking cases with anatomopathologically confirmed lung cancer and never smoking controls undergoing trivial surgery, at 8 Spanish hospitals. The study was conducted between January 2011 and June 2013. Participants were older than 30 and had no previous neoplasms. All were personally interviewed focusing on lifestyle, environmental tobacco smoke exposure, occupational history and leisure time activities (including duration of such activities). Results were analyzed through logistic regression and adjusted also by residential radon and education level. We included 513 never smokers, 191 cases and 322 controls. The OR for those performing the studied leisure time activities was 1.43 (95%CI 0.78–2.61). When we restricted the analysis to those performing do-it-yourself activities for more than 10 years the OR was 2.21 (95%CI 0.93–5.27). Environmental tobacco smoke exposure did not modify this association. The effect for the different lung cancer histological types was very close to significance for adenocarcinoma but only when these activities were performed for more than 10 years. We encourage health professionals to recommend protective measures for those individuals while performing these hobbies to reduce the risk of lung cancer. - Highlights: • Some leisure time activities are associated with the exposure to carcinogenic substances. • These activities are model-making, painting (artistic or not), furniture refinishing or wood working. • Few studies have assessed lung cancer risk due to these hobbies and none in never-smokers. • Leisure activities related to exposure to carcinogenic substances present higher lung cancer risk. • The risk is higher when these activities are performed for more than 10 years.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS2004

Did a Gamma-Ray Burst Initiate the Late Ordovician Mass Extinction?

Gamma-ray bursts (hereafter GRB) produce a flux of radiation detectable across the observable Universe. A GRB within our own galaxy could do considerable damage to the Earth's biosphere; rate estimates suggest that a dangerously near GRB should occur on average several times per billion years. At leastfive times in the history of lfe, the Earth experienced mass extinctions that eliminated a large percentage of the biota. Many possible causes have been documented, and GRB may also have contributed. The late Ordovician mass extinction approximately 440 million years ago may be at least partly the result of a GRB. Due to severe depletion of the ozone layer, intense solar ultraviolet radiation is expected to result from a nearby GRB, and some of the patterns of extinction and survivorship at this time may be attributable to elevated levels of UV radiation reaching the Earth. In addition a GRB could trigger the global cooling which occurs at the end of the Ordovician period that follows an interval of relatively warm climate. Intense rapid cooling and glaciation at that time, previously identijied as the probable cause of this mass extinction, may have resultedfiom a GRB.

Melott, A. L.↗

DOE OSTI2013

In-Cylinder Reaction Chemistry and Kinetics During Negative Valve Overlap Fuel Injection Under Low-Oxygen Conditions

Fuel injection into the negative valve overlap (NVO) period is a common method for controlling combustion phasing in homogeneous charge compression ignition (HCCI) as well as other forms of advanced combustion. During this event, at least a portion of the fuel hydrocarbons can be converted to products containing significant levels of H2 and CO, as well as other short chain hydrocarbons by means of thermal cracking, water-gas shift, and partial oxidation reactions, depending on the availability of oxygen and the time-temperature-pressure history. The resulting products alter the autoignition properties of the combined fuel mixture for HCCI. Fuel-rich chemistry in a partial oxidation environment is also relevant to other high efficiency engine concepts (e.g., the dedicated EGR (D-EGR) concept from SWRI). In this study, we used a unique 6-stroke engine cycle to experimentally investigate the chemistry of a range of fuels injected during NVO under low oxygen conditions. Fuels investigated included iso-octane, iso-butanol, ethanol, and methanol. Products from NVO chemistry were highly dependent on fuel type and injection timing, with iso-octane producing less than 1.5% hydrogen and methanol producing more than 8%. We compare the experimental trends with CHEMKIN (single zone, 0-D model) predictions using multiple kinetic mechanisms available in the current literature. Our primary conclusion is that the kinetic mechanisms investigated are unable to accurately predict the magnitude and trends of major species we observed.

6-stroke cycle↗

NASA NTRSDate not supplied

Informing Wildfire Needs: The Expanded User Interface of NASA's Fire Information for Resource Management System (Firms)

As the global community continues to experience, and respond to, living in a changing environment, access to tools, technologies, and timely data utilized by an increasingly diverse set of stakeholders is increasing. This year, 2023, has thus far seen an unprecedented number of extreme events, increasingly driven by changes in the climate and a strong 2023 ENSO pattern. In Canada, a record number of wildfires, and associated weather events, evacuations, and infrastructure and habitat destruction has taken place, and is ongoing. Large swaths of Greece have experienced similar wildfire destruction. Most recently, Maui has experienced destructive wildfires, and early 2023 saw massive wildfires in Chile. NASA's Fire Information for Resource Management System, or FIRMS, has a fifteen-year history of providing timely and comprehensive data and information on wildfires to stakeholders. FIRMS was initially developed in 2007 by the University of Maryland, with funds from NASA's Applied Sciences Program and the United Nations Food and Agriculture Organization (UN FAO), to provide near real-time active fire Locations to natural resource managers that faced challenges obtaining timely satellite-derived fire information. FIRMS has consistently evolved to address the needs of stakeholders Living in a changing environment; in 2012 it transitioned to NASA LANCE and in 2021 through a partnership between NASA and the US Forest Service, an updated version of FIRMS was released for the US and Canada. As NASA and other federal agencies continue to accelerate Open Science through integrated efforts such as the Year of Open Science, the provision of readily discoverable, findable, accessible, interoperable, reusable data represents a major focus to facilitate equitable outcomes. FIRMS supports this acceleration in Open Science by continuing to provision data and information for its traditional user base, while addressing the novel user needs of an increasingly diverse set of stakeholders seeking robust, reliable, transparently generated data and information. Increasingly, FIRMS is utilized by citizen scientists and individuals directly affected by wildfires - through evacuations, risks to structures/homes, poor air quality. etc. FIRMS has also been Leveraged to detect and assess the impacts resulting from ongoing conflicts. This further highlights the multi-faceted impacts of wildfires and other events. In the Fall of 2023, FIRMS will release an expanded User Interface (UI). This interface captures and reflects the needs of, and input from, a multitude of users. These users range from federal agency representatives to non-government organizations to the private sector to citizen science entities. To respond to this expansive and diverse user need base, the updated FIRMS UI will capture a range of features to support those beginning to explore the range of data and tools available to inform wildfire awareness and knowledge. These users are supported through a Basic Mode interface, furnishing access to a light set of functionalities that provision straight-forward, readily usable information and data, and ingestible knowledge. The Advanced Mode interface supports those stakeholder groups already proficient in navigating FIRMS. These stakeholders, representing fire managers and others, perform active fire management and tactical wildfire response activities. For these stakeholders, additional datasets have been included which require in-depth knowledge of both the utility as well as the caveats of such datasets. Additional functionalities have also been embedded to aid specific user queries. The expanded UI will introduce a new Experimental Mode. The focus of this UI will be to support the provision of emerging and innovative datasets that are in development for review and comment by the user community Examples include post-fire products generated by NASA's Earth Information System (EIS) Fire. This presentation will provide an overview of the expanded FIRMS UI. We will discuss how this UI is designed to be scalable and support the unique needs of an expanding and diverse user base. We will highlight key features, elements, and datasets, and describe how user needs have informed and guided the design of the UI. We will also share recent use cases to convey, and increase awareness, among conference participants. As the global community faces more extreme wildfires, due to climate variability and change, there is an increased need for reliable data to inform, manage, and mitigate the impacts of these events. Through this work, NASA FIRMS is striving to level the playing field, by making information accessible to all; from policy makers to the private sector to historically marginalized communities. In doing so, NASA is promoting the all-hands-on-deck response needed to minimize the impacts of wildfires and harness the strengths of open science to address the greatest environmental challenge faced.

Jenny Hewson↗

DOE OSTI2023

The miniJPAS survey: AGN and host galaxy coevolution of X-ray-selected sources

Studies indicate strong evidence of a scaling relation in the local Universe between the supermassive black hole mass (MBH) and the stellar mass of their host galaxies (M * ). They even show similar histories across cosmic times of their differential terms: the star formation rate (SFR) and black hole accretion rate (BHAR). However, a clear picture of this coevolution is far from being understood. We selected an X-ray sample of active galactic nuclei (AGN) up to z = 2.5 in the miniJPAS footprint. Their X-ray to infrared spectral energy distributions (SEDs) have been modeled with the CIGALE code, constraining the emission to 68 bands, from which 54 are the narrow filters from the miniJPAS survey. For a final sample of 308 galaxies, we derived their physical properties, such as their M * , SFR, star formation history (SFH), and the luminosity produced by the accretion process of the central BH (L AGN ). For a subsample of 113 sources, we also fit their optical spectra to obtain the gas velocity dispersion from the broad emission lines and estimated the M BH . We calculated the BHAR in physical units depending on two radiative efficiency regimes. We find that the Eddington ratios (λ Edd ) and its popular proxy (L X /M * ) have a difference of 0.6 dex, on average, and a KS test indicates that they come from different distributions. Our sources exhibit a considerable scatter on the MBH - M * scaling relation, which can explain the difference between λ Edd and its proxy. We also modeled three evolution scenarios for each source to recover the integral properties at z = 0. Using the SFR and BHAR, we show a notable diminution in the scattering between MBH - M * . For the last scenario, we considered the SFH and a simple energy budget for the AGN accretion, and we retrieved a relation similar to the calibrations known for the local Universe. Our study covers ~1 deg 2 in the sky and is sensitive to biases in luminosity. Nevertheless, we show that, for bright sources, the link between the differential values (SFR and BHAR) and their decoupling based on an energy limit is the key that leads to the local M BH - M * scaling relation. In the future, we plan to extend this methodology to a thousand degrees of the sky using JPAS with an X-ray selection from eROSITA, to obtain an unbiased distribution of BHAR and Eddington ratios.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2016

An Invited Preface for the Following Book: Astrobiologia, Uma Ciencia Emergente

Since the dawn of civilization, we have beheld at the beauty and wonder of the natural world around us and wondered how it came to be. We have pondered the past, and have been intrigued about the future. For this we are unique. Our ancestors looked to the vastness of space and thought surely there are others out there. We are now at a new time in human history where we can address these age-old questions with a scientific approach and study rigorously the three big questions of astrobiology: Where do we come from? Where are we going? and Are we alone? These fundamental questions of astrobiology correspond to those of humanity, and arguably, what makes us human. And so we cannot help but be drawn to the field. Unlike other scientific disciplines, Astrobiology draws on the latest advances in a multitude of fields, from evolutionary and molecular biology, to prebiotic and interstellar chemistry, from astrophysics to astronomy, with a healthy dose of earth and planetary science. Astrobiology is in reality a "metadiscipline" drawing on useful science wherever it is to be found. From a practical point of view, this endeavor requires the interaction of scientists who might not normally meet each other, much less work on a common research project. And, unlike most other scientific disciplines, Astrobiology has implications for how we see ourselves, and how we interact with the earth and beyond. "Where do we come from" touches on the "why" questions that have intrigued not just scientists but philosophers and theologians. "Where are we going" adds to these an economic and political involvement that is currently being played out with discussions of climate change. "And are we alone" will someday force us to face the fact that we as living creatures are not unique, or perhaps that we are utterly alone in the universe, the result of a chemical history that was so improbable as to result in a sample size of one. Either result will force ethical considerations of either "the other" and their relationship to us, or our solitude and thus responsibility as the only life form in our cosmos. So what is Astrobiology? Let's start with the "Where do we come from?" A biologist will approach this looking at the evolution of life on earth, using such traditional tools as comparative anatomy and paleontology and newer tools such as molecular techniques. But this doesn't address why this happened the way it did without a comprehensive understanding of the environment. What was the temperature at such and such a time? Was the earth in a snowball phase or being bombarded by meteorites -- or even just a single large, well-placed one such as struck off the Yucatan peninsula 65 million years ago. This event could not have been predicted by population genetics alone, yet it had the most profound influence on our evolution as without it, we could still be in a world dominated by dinosaurs with the mammals cowering under cover. But it is not enough to go back to LUCA, the Last Universal Common Ancestor of all extant life. One must go back to the dawn of life. How did life arise? What was the environmental backdrop that allowed it to happen? How did we happen to end up with a habitable planet? Indeed, what is the origin and evolution of our solar system, galaxy, biogenic elements all the way back to the Big Bang. The "Where are we going?" tends to be ignored in many astrobiology programs, but in fact this is of the most immediate importance to us. Whereas the past was dominated by physical and chemical processes, and organismal interactions, the future has a new major player: us. While we probably don't have the power (yet) to stop our galaxy passing through another, or even reset the sun or stop the movement of the moon away from the earth, all of these things will influence the future of life on earth. We are already proving that we have the power to visit other bodies in our solar system, either with humans or our robotic surrogates. We are changing our atmospheric composition and thus our climate. We have the power to render species extinct, including our own. But we also have the power to use these tools for the common good, to extend our lifetimes and reclaim our rivers and forests. Which will it be? And then there is the question where science fiction becomes a reality: "Are we alone?" While many people are anxious to find signs of intelligent life out there, such a creature may not share either our curiosity or values. But what if there was a beneficent alien civilization that could communicate with us, perhaps forging a mutual understanding? More likely in the forseeable future is finding a small life, less evolved, life form. Note I did not use the word "simple" as there is nothing "simple" about life, ever. Which brings us back to the question: what is life? So where does Brazil come in? For nearly a decade there has been interest in a Brazilian astrobiology program, from a small side meeting held by the Brazilian Exobiology Program (BEP) of the Brazilian National Research Council, held in Rio de Janeiro, Brazil, on August 12, 2009, in association with the IAU Assembly to subsequent workshops held in several locations and membership of the Brazilian program in the NASA Astrobiology Institute (NAI). Each time I go to Brazil, I am impressed by the enthusiasm of the community, both scientific and student, the latter an excellent omen for the future of astrobiology in Brazil. Facilities are being built to supplement the natural laboratories that Brazil is blessed to have. In my own lab I have been privileged to have a wonderful Brazilian postdoctoral fellow, Dr. Ivan Paulino-Lima, resulting in a daily reminder of the program. I am honored to have been part of the development of astrobiology in Brazil, and hope that this relationship will continue to flourish. Clearly to advance astrobiology needs new knowledge, a reorganization of that which is known, and space missions. To help the reader join on this quest, what follows is a buffet of topics that will allow the reader to nibble on the richness that is Astrobiology. And, like a fabulous meal, it should make you want more. Welcome to Astrobiology.

Are we alone?↗

NASA NTRS2006

Critical Issues in the History of Spaceflight

At a May 1981 "Proseminar in Space History"held at the Smithsonian Institution's National Air and Space Museum (NASM) in Washington, DC, historians came together to consider the state of the discipline of space history. It was an historic occasion. The community of scholars interested in the history of spaceflight was not large; previously, well-meaning but untrained aficionados consumed with artifacts had dominated the field, to the exclusion of the larger context. At a fundamental level, this proseminar represented a "declaration of independence" for what might be called the "new aerospace history." In retrospect, it may be interpreted as marking the rise of space history as a recognizable subdiscipline within the field of U.S. history. Bringing together a diverse collection of scholars to review the state of the art in space history, this proseminar helped in a fundamental manner to define the field and to chart a course for future research. Its participants set about the task of charting a course for collecting, preserving, and disseminating the history of space exploration within a larger context of space policy and technology. In large measure, the course charted by the participants in this 1981 proseminar aided in advancing a very successful agenda of historical research, writing, and understanding of space history. Not every research project has yielded acceptable results, nor can it be expected to do so, but the sum of the effort since 1981 has been impressive. The opportunities for both the exploration of space and for recording its history have been significant. Both endeavors are noble and aimed at the enhancement of humanity. Whither the history of spaceflight? Only time will tell. But there has been an emergent "new aerospace history" of which space history is a central part that moves beyond an overriding concern for the details of the artifact to emphasize the broader role of the spacecraft. More importantly, it emphasizes the whole technological system, including not just the vehicle but also the other components that make up the aerospace climate, as an integral part of the human experience. It suggests that many unanswered questions spur the development of flight and that inquisitive individuals seek to know that which they do not understand.

Dick, Steven J.↗

NASA NTRS2001

SNC Meteorites, Organic Matter and a New Look at Viking

Recently, evidence has begun to grow supporting the possibility that the Viking GC-MS would not have detected certain carboxylate salts that could have been present as metastable oxidation products of high molecular weight organic species. Additionally, despite the instrument's high sensitivity, the possibility had remained that very low levels of organic matter, below the instrument's detection limit, could have been present. In fact, a recent study indicates that the degradation products of several million microorganisms per gram of soil on Mars would not have been detected by the Viking GC-MS. Since the strength of the GC-MS findings was considered enough to dismiss the biology packet, particularly the LR results, any subsequent evidence suggesting that organic molecules may in fact be present on the Martian surface necessitates a re-evaluation of the Viking LR data. In addition to an advanced mass spectrometer to look for isotopic signatures of biogenic processes, future lander missions will include the ability to detect methane produced by methanogenic bacteria, as well as techniques based on biotechnology. Meanwhile, the identification of Mars samples already present on Earth in the form of the SNC meteorites has provided us with the ability to study samples of the Martian upper crust a decade or more in advance of any planned sample return missions. While contamination issues are of serious concern, the presence of indigenous organic matter in the form of polycyclic aromatic hydrocarbons has been detected in the Martian meteorites ALH84001 and Nakhla, while there is circumstantial evidence for carbonaceous material in Chassigny. The radiochronological ages of these meteorites are 4.5 Ga, 1.3 Ga, and 165 Ma respectively representing a span of time in Earth history from the earliest single-celled organisms to the present day. Given this perspective on organic material, a biological interpretation to the Viking LR results can no longer be ruled out. In the LR experiment, a solution containing C-14 labeled organic compounds was injected into soil samples. The detection of radioactivity in the overhead space would indicate that one or more of the substrates had been chemically converted into a carbon-containing gas. To serve as a control, some samples were heated enough to destroy most known terrestrial microbes so that an indication for life would be a positive response from unheated samples and a negative response from heated samples. On Mars, the LR results had met minimum criteria for a biological interpretation but due to the GC-MS results, the LR responses were later attributed to putative soil inorganic oxidants. Since the time of Viking, studies have been carried out with the objective of determining an oxidant or combination of oxidants that might exist on Mars and have produced the observed kinetics of the LR response. To date, no such agent has been found that produces all aspects of the LR results on Mars. While the above considerations in no way imply the existence of life forms at the two Viking landing sites, inorganic and biological explanations for the Viking LR data should now be considered equally plausible until more complete studies of the Martian surface are carried out. Therefore, in light of the SNC meteorites data and their implications for the possibility of organic matter near or on the Martian surface the Viking biology experiments should thus be seen, not as failures for their inability to provide unambiguous evidence for or against Martian life, but as a foundation for the development of future life-detection instruments. Additional information is contained in the original extended abstract.

Warmflash, David M.↗

NASA NTRS2020

The Roughness Properties of Small Ice-Bearing Craters at the South Pole of the Moon: Implications for Accessing Fresh Water Ice in Future Surface Operations

The lunar poles provide a fascinating thermal environment capable of cold-trapping water ice on geologic timescales [1]. While there have been many observations indicating the presence of water ice at the lunar surface [e.g., 2–4], it is still not clear when this ice was delivered to the Moon. The timing of volatile dep-osition provides important constraints on the origin of lunar ice because different delivery mechanisms have been active at different times throughout lunar history. We previously found that some small (<10 km) cra-ters at the south pole of the Moon have morphologies suggestive of relatively young ages, on the basis of crisp crater rims [5]. These craters are too small to date with robust cratering statistics [5], but the possibility of ice in young craters is intriguing because it suggests that there is some recent and perhaps ongoing mechanism that is delivering or redistributing water to polar cold traps. Therefore, understanding if these small, ice-bear-ing craters are indeed young is essential in understand-ing the age and source of volatiles on the Moon. Here we take a new approach to understand the ages of these small polar cold traps: analyzing the roughness properties of small ice-bearing craters. It is well under-stood that impact crater properties (e.g., morphology, rock abundance, and roughness) evolve with time due to a variety of geologic and space-weathering processes [6–11]. Topographic roughness is a measurement of the local deviation from the mean topography, providing a measurement of surface texture, and is a powerful tool for evaluating surface evolution over geologic time [e.g., 11–14]. In this study we analyze the roughness of southern lunar craters (40°S–90°S) from all geologic eras, and determine how the roughness of small (<10 km) ice-bearing craters compare. We discuss the implications of the ages of ice-bearing south polar craters, and potential strategies for accessing fresh ice on the Moon.

Deutsch, Ariel N.↗

DOE OSTI2026

Thermal Gradient Effects on Redox Evolution and Volatility-Driven Fractionation in Ternary U/Ce/Cs Condensates

Understanding how thermal history influences redox evolution and chemical fractionation is essential for characterizing high-temperature condensation in complex materials, including nuclear debris. Here, we tested the hypothesis that distinct thermal regimes in a plasma flow reactor influence redox pathways and elemental partitioning in ternary U/Ce/Cs systems. A configurable plasma flow reactor was modified with an external tube furnace to impose two distinct thermal gradients: continuous ambient cooling and a furnace-assisted thermal hold-up near 1400 K followed by rapid cooling. Transmission electron microscopy characterized phase identity, morphology, and nanoscale element distributions, while inductively coupled plasma-mass spectrometry quantified bulk elemental ratios. Across both thermal regimes, uranium and cerium condensed as UO 2 and CeO 2 as dominant refractory oxide products. Uranium partially oxidized to α-UO 3 during extended ambient cooling, while furnace-assisted hold-up preserved UO 2 and produced partial reduction of cerium to Ce 2 O 3 . Cesium remained volatile upstream and condensed later in the reactor, forming Cs 2 O and Cs-uranate phases with the highest incorporation after thermal hold-up. Bulk ICP-MS measurements supported these observations. U/Ce ratios remained comparatively stable and Cs displayed delayed and apparent transient enrichment that matched the nanoscale measurements. This integrated approach provides a quantitative method for linking thermal gradients to redox evolution and volatility-driven fractionation. These results show how the plasma flow reactor can identify where equilibrium descriptions remain adequate and where kinetic effects from residence time and temperature history must be considered when interpreting condensation behavior in multicomponent systems.

and nuclear chemistry↗

NASA NTRS1991

The history of lunar volcanism

The timing and extent of volcanism must have reflected the internal thermal evolution of the moon and a knowledge of the history of lunar volcanism is important for understanding the global evolution of the moon. Recent studies show that lunar volcanism began prior to formation of at least some of the major lunar basins, although the exact provenance of the earliest volcanism remains somewhat obscure. It was shown that the ferroan anorthosites are the best candidates to be remnants of the postulated lunar magma ocean. The Mg-suite rocks are the second major category of highland rocks, and highly evolved granites and quartz-monzodiorites comprise a third suite of lunar highland rocks. Basalts form the Apollo 12, 15, and 17 landing sites demonstrated that the lunar mantle is greatly depleted in LREE beneath the widely separated landing sites, an observation supportive of a global process of differentiation. Also, KREEP volcanism apparently predated basin formation in the Serenitatis region, but appears to have been contemporaneous with basin formation in the Imbrium region. Recent studies showed that the earliest lunar basaltic volcanism was of mare-like composition.

Nyquist, Laurence E.↗