cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.48577/jpl.7p3ecb
title: Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable Lander

description: NASA’s Dragonﬂy mission will send a rotorcraft lander to the surface of Titan. Dragonﬂy’s science themes include investigation of Titan’s prebiotic chemistry, habitability, and potential chemical biosignatures in both liquid water (as might occur in the interior mantle ocean, in cryovolcanic ﬂows, and/or in impact melt) and in liquid hydrocarbon (within Titan’s lakes, seas, and/or alkanofers). Consideration of both of these solvents simultaneously led to the targeting of Titan’s dunes and interdunes to sample organic sediments and water ice respectively. Ultimately, Dragonﬂy’s traverse target is 80-km Selk Crater, where we seek previously liquid water that had mixed with surface organics. Our science goals include determining how far prebiotic chemistry has progressed on Titan and what molecules and elements might be available for such chemistry. We will also determine the role of Titan’s tropical deserts in the global methane cycle. We will investigate the rates and processes modifying Titan’s surface geology and constrain how and where organics and liquid water can mix on and within Titan. And we will search for chemical biosignatures indicative of past or extant biological processes. As such, Dragonﬂy is the ﬁrst NASA mission to explicitly incorprate searching for life into its mission goals since the Viking landers in 1977.
DOI: 10.48577/jpl.gmlp5v
title: Passive Microwave Signatures and Retrieval of High-latitude Snowfall over Open Oceans and Sea Ice: Insights from Coincidences of GPM and CloudSat Satellites

description: This paper studies changes in microwave signals of oceanic snowfall in response to formation of snow-covered sea ice using active and passive coincident data from the radar and radiometer onboard the CloudSat and the Global Precipitation Measurement satellites. Using reanalysis data of liquid and ice water path as well as satellite retrievals of sea ice snow-cover depth, spectral regions are determined over which the snowfall signatures are likely to be obscured or falsely detected. Relying on an a-priori database populated with the active-passive coincidences, a Bayesian snowfall retrieval algorithm is presented that links a k-nearest neighbor matching with the inverse Gaussian estimator used in the Goddard Profiling algorithm. Without relying on any ancillary data of air temperature, the results demonstrate that over open oceans (sea ice), we can passively retrieve the CloudSat active snowfalls with true positive rate of 91 (87%) and the root mean squared error of 0.25 (0.14) mm/hr.
DOI: 10.48577/jpl.bdykcu
title: Exploration of Icy Ocean Worlds using Geophysical Approaches

description: Geophysics-focused missions are critical for the future exploration of icy ocean worlds. Of particular interest is the exploration of the Galilean moon Europa and the Saturnian moons Titan and Enceladus. These bodies likely have geologically active surfaces and may harbor habitable subsurface environments. Placing any candidate signatures for life in context requires further knowledge of the interior of these worlds. While the surfaces of these bodies have been mapped, their interiors remain poorly constrained. Geophysical approaches such as geodesy, seismology, radar and altimetry measurements, and electromagnetometry would provide critical information regarding the interior of these icy ocean worlds. The approaches described below would answer key science questions regarding the ice shell and ocean dynamics, internal structure and interior layers' thicknesses, near-surface structure, and how material from the deep interior might be exchanged with the surface. Here we outline the geophysical environments of Enceladus, Europa, and Titan, some outstanding science questions that need to be addressed, and examples of the geophysical approaches that can provide the context to better understand icy ocean worlds.
DOI: 10.48577/jpl.kzit7h
title: Improved methane emission estimates using AVIRIS-NG and an Airborne Doppler Wind Lidar

description: This study demonstrates the utility of combining Airborne Doppler Wind Lidar (ADWL) measurements and quantitative methane (CH4) retrievals from the Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-NG) to estimate CH4 emission rates. In a controlled release experiment, Twin Otter Doppler Wind Lidar (TODWL) observed wind speed and direction agreed closely with sonic anemometer measurements and CH4 emission rates derived from TODWL observations were more accurate than those using the sonic during periods of stable winds. During periods exhibiting rapid shifts in wind speed and direction, estimating emission rates proved more challenging irrespective of the use of model, sonic, or TODWL wind data. Overall, TODWL was able to provide accurate wind measurements and emission rate estimates despite the variable wind conditions and excessive flight level turbulence which impacted near surface measurement density. TODWL observed winds were also used to constrain CH4 emissions at a refinery, landfill, wastewater facility, and dairy digester. At these sites, TODWL wind measurements agreed well with wind observations from nearby meteorological stations, and when combined with quantitative CH4 plume imagery, yielded emission rate estimates that were similar to those obtained using model winds. This study demonstrates the benefits of combining TODWL and AVIRIS-NG CH4 measurements and emphasizes the potential benefits of integrating both instruments on a single aircraft for future deployments.
DOI: 10.48577/jpl.pxzr1z
title: Optimal Modal Truncation

description: This paper revisits the modal truncation from an optimisation point of view. Inparticular, the concept of dominant poles is formulated with respect to different systemsnorms as the solution of the associated optimal modal truncation problem. The latter isreformulated as an equivalent convex integer or mixed-integer program. Numericalexamples highlight the concept and optimisation approach.
DOI: 10.48577/jpl.3y9jj9
title: Land Surface Temperature from GOES-East and GOES-West

description: Land surface temperature (LST) is an important climate parameter that controls the surface energy budget. For climate applications, information is needed at global scale with representation of the diurnal cycle. To achieve global coverage there is a need to merge about five independent geostationary satellites (GEO) that have different observing capabilities. An issue of practical importance is the merging of independent satellite observations in areas of overlap. An optimal approach in such areas could eliminate the need for redundant computations by differently viewing satellites. We use a previously developed approach to derive information on LST from GOES east (GOES-E), modify it for application to GOES west (GOES-W) and implement it simultaneously across areas of overlap at 5-km spatial resolution. We evaluate the GOES based LST against in-situ observations and an independent MODIS product for the period of 2004–2009. The methodology proposed minimizes differences between satellites in areas of overlap. The mean and median values of the differences in monthly mean LST retrieved from GOES-E and GOES-W at UTC 06 for July are 0.01° and 0.11° K, respectively. Similarly, at UTC 18 the respective mean and median value of the differences were 0.15° and 1.33° K. These findings can provide guidelines for potential users to decide whether the reported accuracy based on one satellite alone, meets their needs in area of overlap. Since the six year record of LST was produced at hourly time scale, the data are well suited to address scientific issues that require the representation of LST diurnal cycle or the diurnal temperature range (DTR).
DOI: 10.48577/jpl.bdvwga
title: The Likely Thickness of Europa's Icy Shell

description: The icy outer shell of Jupiter's moon Europa is believed to be geologically active, and geological processes within the ice may be key to sustaining chemical disequilibria and potentially habitable environments within the icy shell and ocean. Currently, there is insufficient observational data to determine the thickness of the icy shell, obfuscating crucial aspects of interior processes. Although a range of icy shell thicknesses ( 10􀀀1{102 km) have been proposed, not all are equally likely given the current knowledge of Europa. In this study, I construct a probability density distribution for Europa's present-day mean icy shell thickness using a heat flux balance, assuming a simple two-layered model consisting of a partially porous conductive upper layer, and a ductile interior layer that may be experiencing solid-state convection. Current best estimate (CBE) values and uncertainties for 20 key parameters are propagated through this steady-state heat heat influx balance to construct 107 independent simulations. Additionally, I estimate present day values for the icy shell layer thicknesses, the rocky interior and icy heat fluxes, icy shell thermal properties, and convective ice viscosity. I predict Europa's total icy thickness to be 23{47 km, with a CBE thickness of 24:3+22:8 􀀀1:5 km. This result is highly skewed; icy shells many tens-of-kilometers thick are much more probable than icy shells &lt; 10 km thick. The resulting distributions have key implications for future spaceborne, landed, and subsurface exploration of Europa, as well as studies of icy shell processes, thermal and mechanical state, and habitability across the icy ocean worlds.
DOI: 10.48577/jpl.epoldj
title: MOSAIC: A satellite constellation to enable groundbreaking Mars climate system science and prepare for human exploration.

description: The Martian climate system has been revealed to be at least as complex as Earth’s. Over the last 20 years a fragmented and incomplete picture has emerged of its structure and variability; we remain largely ignorant of many of the physical processes that drive matter and energy flow between and within Mars’ diverse climate domains. Mars Orbiters for Surface, Atmosphere, and Ionosphere Connections (MOSAIC) is a constellation of ten platforms focused on understanding these climate connections, with orbits and instruments tailored to observe the Mars climate system from three complementary perspectives. First, low circular near-polar sun-synchronous orbits (a large mothership and three smallsats spaced in local time) enable vertical profiling of wind, aerosols, water and temperature, as well as mapping of surface and subsurface ice. Second, elliptical orbits sampling all of Mars’ plasma regions enable multi-point measurements necessary to understand mass/energy transport and ion-driven escape. Last, longitudinally-spaced areostationary orbits enable a) synoptic views of the lower atmosphere necessary to understand global and mesoscale dynamics, b) global views of the hydrogen and oxygen exospheres, and c) upstream measurements of space weather conditions. Motivated by well-established Decadal Survey and Mars Exploration Program Analysis Group (MEPAG) goals, MOSAIC will characterize climate system variability diurnally and seasonally, on meso-, regional, and global scales, targeting the shallow subsurface all the way out to the solar wind, making many first-of-their-kind measurements. Importantly, these measurements will also prepare for human exploration and settlement of Mars by providing valuable water resource prospecting and the forecasting of dust and radiation hazards and ionospheric communication/positioning disruptions.
DOI: 10.48577/jpl.ie6wpt
title: Tiger: Concept Study for a New Frontiers Enceladus Habitability Mission

description: Data returned from the Cassini–Huygens mission have strengthened Enceladus, a small icy moon of Saturn, as an important target in the search for life in our solar system. Information gathered from Cassini to support this includes the presence of a subsurface liquid water ocean, vapor plumes and ice grains emanating from its south polar region, and the detection of essential elements and organic material that could potentially support life. However, several outstanding questions remain regarding the connectivity of plume material to the ocean and the composition of the complex organic material. Herein we introduce Tiger, a mission concept developed during the 2020 Planetary Science Summer School at NASA’s Jet Propulsion Laboratory. Tiger is a flyby mission that would help further constrain the habitability of Enceladus through two science objectives: (1) determine whether Enceladus’s volatile inventory undergoes synthesis of complex organic species that are evidence for a habitable ocean, and (2) determine whether Enceladus’s plume material is supplied directly from the ocean or if it interfaces with other reservoirs within the ice shell. To address the science goals in a total of eight flybys, Tiger would carry a four-instrument payload, including a mass spectrometer, a single-band ice-penetrating radar, an ultraviolet imaging spectrograph, and an imaging camera. We discuss Tigerʼs instrument and mission architecture, as well as the trades and challenges associated with a habitability-focused New Frontiers–class flyby mission to Enceladus.
DOI: 10.48577/jpl.lkkjat
title: Revisiting the Planet Mass and Stellar Metallicity Relation for Low-Mass Exoplanets Orbiting GKM Class Stars

description: Abstract: The growing database of exoplanets have shown us the statistical characteristics 10 of various exoplanet populations, providing insight towards their origins. Observational 11 evidence suggests that the process by which gas giants are conceived in the stellar disk 12 may be disparate from that of smaller planets. Using NASA’s Exoplanet Archive, we an- 13 alyzed relationships between planet mass and stellar metallicity as well as planet mass 14 and stellar mass for low-mass exoplanets (MP &lt; 0.13 MJ) orbiting spectral class G, K, and 15 M stars. We performed further uncertainty analysis to confirm that the exponential law 16 relationships found between the planet mass, stellar mass and the stellar metallicity can- 17 not be fully explained by observation biases alone.
DOI: 10.48577/jpl.i3axha
title: Intermittent methane emissions in the Permian Basin

description: The Permian Basin is the largest and fastest growing oil and gas (O&G) producing region in the United States. We conducted an extensive airborne campaign across the majority of the Permian in September-November 2019 with imaging spectrometers to quantify strong methane (CH4) point source emissions at facility-scales, including high frequency sampling to evaluate intermittency. We identified 1100 unique and heavy-tailed distributed sources that were sampled at least 3 times (average 8 times), showing 26% average persistence. Sources that were routinely persistent (50-100%) make up only 11% of high emitting infrastructure, but 29% of quantified emissions from this population, potentially indicative of leaking equipment that merits repair. Sector attribution of plumes shows that 50% of detected emissions result from O&G production, 38% from gathering and boosting, and 12% from processing. This suggests a 20% relative shift from upstream to midstream compared to other US O&G basins for large emitters. Simultaneous spectroscopic identification of flares found that 12% of detected Permian CH4 plume emissions were associated with either active or inactive flares. Frequent, high-resolution monitoring is necessary to accurately understand intermittent methane super-emitters across large, heterogeneous O&G basins and to efficiently pin-point persistent leaks for mitigation.
DOI: 10.48577/jpl.jgvcyc
title: Fomalhaut b could be massive and sculpting the narrow, eccentric debris disc, if in mean-motion resonance with it

description: The star Fomalhaut hosts a narrow, eccentric debris disc, plus a highly eccentric companion Fomalhaut b. It is often argued that Fomalhaut b cannot have significant mass, otherwise it would quickly perturb the disc. We show that material in internal mean-motion resonances with a massive, coplanar Fomalhaut b would actually be long-term stable, and occupy orbits similar to the observed debris. Furthermore, millimetre dust released in collisions between resonant bodies could reproduce the width, shape and orientation of the observed disc. We first re-examine the possible orbits of Fomalhaut b, assuming that it moves under gravity alone. If Fomalhaut b orbits close to the disc midplane then its orbit crosses the disc, and the two are apsidally aligned. This alignment may hint at an ongoing dynamical interaction. Using the observationally allowed orbits, we then model the interaction between a massive Fomalhaut b and debris. Whilst most debris is unstable in such an extreme configuration, we identify several resonant populations that remain stable for the stellar lifetime, despite crossing the orbit of Fomalhaut b. This debris occupies low-eccentricity orbits similar to the observed debris ring. These large bodies would have a clumpy distribution, but dust released in collisions between them would form a narrow, relatively smooth ring similar to observations. We show that if Fomalhaut b has a mass between those of Earth and Jupiter then, far from removing the observed debris, it could actually be sculpting it through resonant interactions.
DOI: 10.48577/jpl.xhi0ds
title: Toward a global model of the interactions in low-lying states of methyl cyanide: rotational and rovibrational spectroscopy of the v4 = 1 state and tentative interstellar detection of the v4 = v8 = 1 state in Sgr B2(N)

description: Rotational spectra of methyl cyanide were recorded newly and were analyzed together with existing spectra to extend the globalmodel of low-lying vibrational states and their interactions to 34 = 1 at 920 cm􀀀1. The rotational spectra cover large portions ofthe 36􀀀1439 GHz region and reach quantum numbers J and K of 79 and 16, respectively. Information on the K level structure ofCH3CN is obtained from IR spectra. A spectrum of 28 around 717 cm􀀀1, analyzed in our previous study, covered also the 4 band.The assignments in this band cover 880􀀀952 cm􀀀1, attaining quantum numbers J and K of 61 and 13, respectively.The most important interaction of 34 = 1 appears to be with 38 = 3, K = 0, l = +3, a previously characterized anharmonicresonance. We report new analyses of interactions with K = 􀀀2 and l = +1, with K = 􀀀4 and l = 􀀀1, and with K = 􀀀6and l = 􀀀3; these four types of interactions connect all l substates of 38 = 3 in energy to 34 = 1. A known K = 􀀀2, l = +1interaction with 37 = 1 was also analyzed, and investigations of the K = +1, l = 􀀀2 and K = +3, l = 0 resonances with38 = 2 were improved, as were interactions between successive states with 38 3, mainly through new 38 2 rotational data.A preliminary single state analysis of the 34 = 38 = 1 state was carried out based on rotational transition frequencies and on4 + 8 􀀀 8 hot band data. A considerable fraction of the K levels was reproduced within uncertainties in its entirety or in part,despite obvious widespread perturbations in 34 = 38 = 1.In addition to the interstellar detection of rotational transitions of methyl cyanide from within all vibrational states up to 34 = 1,we report the tentative detection of 34 = 38 = 1 toward the main hot molecular core of the protocluster Sagittarius B2(N) employingthe Atacama Large Millimeter/submillimeter Array.
DOI: 10.48577/jpl.dq0sid
title: Fault Zone Heterogeneities Explain Depth-dependent Pattern and Evolution of Slow Earthquakes in Cascadia

description: Slow earthquakes including tremor and slow-slip events are recent additions to the conventional 13 earthquake family and have a close link to megathrust earthquakes. Slow earthquakes along the Cascadia 14 subduction zone display a diverse behavior at different spatiotemporal scales and an intriguing increase of 15 events frequency with depth. However, what causes such variability, especially the depth-dependent 16 behavior is not well understood. Here we build on a heterogeneous asperities-in-matrix fault model that 17 incorporates differential pore pressure in a rate-and-state friction framework to investigate the underlying 18 processes of the observed ETS variability. We find that the variations of effective normal stress (pore 19 pressure) is one important factor in controlling ETS behavior. Our model reproduces the full complexity 20 of ETS patterns and the depth-frequency scaling that agree quantitatively well with observations, 21 suggesting that fault zone heterogeneities can be one viable mechanism to explain a broad spectrum of 22 transient fault behaviors.
DOI: 10.48577/jpl.ex60d6
title: UMaMI: A New Frontiers-style Mission Concept to Explore the Uranian System

description: With the public and scientific community’s growing interest in Ocean Worlds, the icy moons of Uranus offer an ideal opportunity to explore a native Ice Giant satellite system. Although it is uncertain whether any of the Uranian moons currently host subsurface oceans, there is tantalizing evidence that this could be the case—including geologically young surface features and volatiles that are not stable—making these objects possible ocean worlds in their own right. Determining whether subsurface oceans are present in the interiors of these moons would increase our understanding of the conditions under which subsurface oceans are formed and maintained over the history of the Solar System. The presence and stability of a subsurface ocean in the interiors of icy bodies is key to identifying their potential as a habitable environment. In this work, we describe a mid-size (New Frontiers class) mission concept — the Uranian Magnetosphere and Moons Investigator (UMaMI). The magnetosphere and moons are tightly coupled parts of the Uranian system and are complementary to study and necessary to analyze the Uranian moons as potential Ocean Worlds. Additionally, this mission concept includes study of Uranus’s rings, magnetosphere-solar wind interaction, and opportunities for studies of Uranus itself. The proposed mission design focuses on a tour of the moons that would be able to identify current or relict subsurface oceans in the five major moons—Miranda, Ariel, Umbriel, Titania, and Oberon.
DOI: 10.48577/jpl.k4llym
title: A Recipe for Geophysical Exploration of Enceladus

description: Orbital geophysical investigations of Enceladus are critical to understanding its energy balance. We identified key science questions for the geophysical exploration of Enceladus, answering which would support future assessment of Enceladus' astrobiological potential. Using a Bayesian framework, we explored how science requirements map to measurement requirements. We performed mission simulations to study the sensitivity of a single spacecraft and dual spacecraft congurations to static gravity and tidal Love numbers of Enceladus. We find that mapping Enceladus' gravity eld, improving the accuracy of the physical libration amplitude, and measuring Enceladus' tidal response would provide critical constraints on the internal structure, and establish a framework for assessing Enceladus' longterm habitability. This kind of investigation could be carried out as part of a life search mission at little additional resource requirements.