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NASA NTRS1992

Multispectral observations of the Jovian aurora

The upper atmospheres of the Earth and the outer planets form a screen on which precipitating charged particles, like the electron beam in a television, trace fleeting, but revealing patterns of visible, ultraviolet, infrared, and x ray emissions that offer valuable clues to processes occurring within the planetary magnetospheres. At Earth, years of in situ measurements, as well as ground based observations, have yielded a picture (still fuzzy) where the interaction of the solar wind with the magnetosphere of the Earth provides a complex path for the storage and release of energy during magnetic substorms; the ultimate manifestation of terrestrial auroral processes. More recent global imaging of substorm events from high above the Earth (greater than 3.5 R(sub e)) by Dynamics Explorer have made a unique contribution towards understanding the global and temporal evolution of such auroral events by providing a morphological perspective and by providing the crucial observational link that allows the separation of spatial and temporal variations inherent in the interpretation of in situ data. A similar role was played by the Hubble Space Telescope (HST) during the recent encounter of Ulysses with Jupiter in helping to define a new paradigm in Jovian auroral physics. The old paradigm portrayed Jupiter's magnetosphere as totally dominated by internal processes (i.e. Io related tori, heavy ions, etc.) where energetic heavy ion precipitation in the inner magnetosphere was solely responsible for the observed auroral phenomena. Ulysses and HST portray a more Earth-like paradigm where electron acceleration in the outer magnetosphere near the boundary with the solar wind plays a distinct role in the formation of auroral hot spots, yet energetic heavy ions also enter into the picture (similar to the role of the energetic ions from the terrestrial ring current during magnetic substorms). These heavy ions as a result of excitation during their transit through the atmosphere produce the x ray emissions observed in Roentgensatellit (ROSAT) x ray energy spectra.

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NASA NTRS2003

NASA's Far-Infrared/Submillimeter Roadmap Missions

Information vital to the attainment of the major scientific objectives of NASA s Origins and Structure and Evolution of the Universe themes is uniquely available in the far-IR and submillimeter (FIR/SMM). NASA is studying concepts and investing in technologies for FIF/SMM telescopes that could fly in the decade 201 0 - 2020 and provide enormous increases in measurement capabilities to extend the legacy of the next-generation missions SlRTF and Herschel. Future FIR/SMM space observatories will have the sensitivity needed to reach back in time to the formation epoch of the first luminous objects, the angular resolution needed to image proto-planetary systems and distinguish the emissions of individual galaxies, and the spectral resolution needed to probe the physical conditions and measure the flows of interstellar gas in young galaxies, nascent stars, and the dust-enshrouded nuclei of galaxies that harbor massive black holes. NASA s infrared roadmap includes the JWST-class Single Aperture Far-IR (SAFIR) telescope and FIR/SMM interferometers. The talk will give the scientific motivation for these missions, describe mission concepts and telescope measurement capabilities, and compare these capabilities with those of the next-generation IR telescopes and with the complementary JWST and ALMA.

Leisawitz, David↗

NASA NTRSDate not supplied

A window on the composition of the early solar nebula: 2014MU69, Pluto, and Phoebe

The initial chemical composition of any solar nebula will depend upon the degree to which 1) organic and ice components form on dust grains, 2) organic and molecular species form in the gas phase, 3) organics and ices are exchanged between the gas and solid state, and 4) the precursor and newly formed (more complex) materials survive and are modified in the developing planetary system. Infrared and radio observations of star-forming regions reveal that complex chemistry occurs on icy grains, sometimes before stars even form. Additional processing, through the protosolar disk and within the solar nebula further modifies most, but probably not all, of the initial materials. In fact, the modern Solar System still carries a fraction of its interstellar inheritance [Alexander et al., 2017]. Here we focus on three examples of small bodies in our Solar System, each containing chemical and dynamical clues to its origin and evolution: the small, cold-classical Kuiper Belt object (KBO) 2014MU69 , Pluto and Saturn’s moon, Phoebe. The New Horizons flyby of 2014 MU69 has given the first view of an unaltered body composed of material originally in the solar nebula at ~45 AU. The spectrum reveals methanol ice (not commonly found), a possible detection of water ice (Stern et al. 2019). Pluto’s internal and surface inventory of volatiles and complex organics, together with active geological processes including cryo-volcanism, indicate a surprising level of activity on a body in the outermost region of the Solar System, and the fluid that emerges from subsurface reservoirs may contain material inherited from the solar nebula (Cruikshank et al. 2019). Meanwhile, Saturn's captured moon, Phoebe, carries high D/H in H2O [Clark et al. 2018)], and complex organics (Cruikshank et al. 2008), both consistent with its formation in, and inheritance from, the outer solar nebula. Together, these objects provide windows on the origin and evolution of our Solar System and constraints to be considered in future chemical and physical models of PPDs. The Spitzer Space telescope discovered the ring of dust around Saturn that emanated from the bombardment of Phoebe in the recent past, dislodging primitive Solar System material from deep within that satellite. In addition, Spitzer has provided detailed studies of the chemistry of star forming regions where methanol and other ices are readily observed. As a result of these and other observations, protoplanetary disk models are beginning to combine both dynamical and chemical complexities into their codes, resulting in new insights for exoplanetary systems.

Yvonne J. Pendleton↗

NASA NTRS1988

Exploration Studies Technical Report - Volume 2: Studies Approach and Results

The NASA Office of Exploration has been tasked with defining and recommending alternatives for an early 1990's national decision on a focused program of human exploration of the solar system. The Mission Analysis and System Engineering (MASE) group, which is managed by the Exploration Studies Office at the Johnson Space Center, is responsible for coordinating the technical studies necessary for accomplishing such a task. This technical report describes the process that has been developed in a case study approach. The four case studies that were developed in FY88 include: 1. Human expedition to Phobos 2. Human expeditions to Mars 3. Lunar observatory 4. Lunar outpost to early Mars evolution The final outcome of this effort is a set of programmatic and technical conclusions and recommendations for the following year's work. Volume 2 describes the case study process, the technical results of each of the case studies, and opportunities for additional study. Included in the discussion of each case study is a description of the mission key features and profile. Mission definition and manifesting are detailed, followed by a description of the mission architecture and infrastructure. Systems concepts for the required orbital nodes, transportation systems, and planetary surface systems are discussed. Prerequisite implementation plans resulting from the synthesized case studies are described and in-depth assessments are presented.

Interplanetary flight↗

NASA NTRS1993

Aspects of modelling the tectonics of large volcanoes on the terrestrial planets

Analytic solutions for the responses of planetary lithospheres to volcanic loads have been used to model faulting and infer elastic plate thicknesses. Predictions of the distribution of faulting around volcanic loads, based on the application of Anderson's criteria for faulting to the results of the models, do not agree well with observations. Such models do not give the stress state in the load itself, but only suggest a state of horizontal compressive stress there. Further, these models have considered only the effect of an instantaneously emplaced load. They do not address the time evolution of stresses, nor do they consider the effect of a load which grows. A finite element approach allows us to assign elements to the load itself, and thus permits calculation of the stress state and stress history within the edifice. The effects of episodic load growth can also be treated. When these effects are included, models give much better agreement with observations. We use the finite element code TECTON to construct axisymmetric models of volcanoes resting on an elastic lithospheric plate overlying a viscoelastic asthenosphere. We have implemented time-dependent material properties in order to simulate incremental volcano growth. The viscoelastic layer was taken to extend to a sufficient depth so that a rigid lower boundary has no significant influence on the results. The code first calculates elastic deformations and stresses and then determines the time-dependent viscous deformations and stresses. Time in the model scales as the Maxwell time tau(m) in the asthenosphere. We consider a volcano 25 km in height and 200 km in radius on an elastic lithosphere 40 km thick (parameters approximately appropriate to Ascraeus Mons). The volcano consists of three load increments applied at intervals of 1000 tau(m). Contours of maximum deviatoric stress in the fully-grown edifice at the conclusion of flexure (t = 3000 tau(m)) are shown.

Mcgovern, Patrick J.↗

NASA NTRS2005

HyperPASS, a New Aeroassist Tool

A new software tool designed to perform aeroassist studies has been developed by Global Aerospace Corporation (GAC). The Hypersonic Planetary Aeroassist Simulation System (HyperPASS) [1] enables users to perform guided aerocapture, guided ballute aerocapture, aerobraking, orbit decay, or unguided entry simulations at any of six target bodies (Venus, Earth, Mars, Jupiter, Titan, or Neptune). HyperPASS is currently being used for trade studies to investigate (1) aerocapture performance with alternate aeroshell types, varying flight path angle and entry velocity, different gload and heating limits, and angle of attack and angle of bank variations; (2) variable, attached ballute geometry; (3) railgun launched projectile trajectories, and (4) preliminary orbit decay evolution. After completing a simulation, there are numerous visualization options in which data can be plotted, saved, or exported to various formats. Several analysis examples will be described.

Gates, Kristin↗

NASA NTRS2012

Ground-Based Centimeter, Millimeter, and Submillimeter Observations of Recent Comets

Comets provide important clues to the physical and chemical processes that occurred during the formation and early evolution of the Solar System, and could also have been important for initiating prebiotic chemistry on the early Earth [I]. Comets are comprised of molecular ices, that may be pristine interstellar remnants of Solar System formation, along with high-temperature crystalline silicate dust that is indicative of a more thermally varied history in the protosolar nebula [2]. Comparing abundances of cometary parent volatiles, and isotopic fractionation ratios, to those found in the interstellar medium, in disks around young stars, and between cometary families, is vital to understanding planetary system formation and the processing history experienced by organic matter in the so-called interstellar-comet connection [3]. In the classical picture, the long-period comets probably formed in the nebular disk across the giant planet formation region (5-40 AU) with the majority of them originating from the Uranus-Neptune region. They were subsequently scattered out to the Oort Cloud (OC) by Jupiter. The short-period comets (also known as ecliptic or Jupiter Family Comets - JFC) reside mainly in the Edgeworth-Kuiper belt where they were formed. Given the gradient in physical conditions expected across this region of the nebula, chemical diversity in this comet population is to be expected [4,5]. We have conducted observations of comets I 03P/Hartley 2 (JFC) and C/2009 PI (Garradd) (OC), at primarily millimeter and submillimeter wavelengths, to determine important cosmogonic quantities, such as the ortho:para ratio and isotope ratios, as well as probe the origin of cometary organics and if they vary between the two dynamic reservoirs.

Milam, S. N.↗

NASA NTRS2013

Multiwavelength Observations of Recent Comets

ground-based observations↗

NASA NTRS2004

Lunar and Planetary Science XXXV: Special Session: Oxygen in the Solar System, I

The Special Session: Oxygen in the Solar System, I, included the following reports:Oxygen in the Solar System: Origins of Isotopic and Redox Complexity; The Origin of Oxygen Isotope Variations in the Early Solar System; Solar and Solar-Wind Oxygen Isotopes and the Genesis Mission; Solar 18O/17O and the Setting for Solar Birth; Oxygen Isotopes in Early Solar System Materials: A Perspective Based on Microbeam Analyses of Chondrules from CV Carbonaceous Chondrites; Insight into Primordial Solar System Oxygen Reservoirs from Returned Cometary Samples; Tracing Meteorites to Their Sources Through Asteroid Spectroscopy; Redox Conditions Among the Terrestrial Planets; Redox Complexity in Martian Meteorites: Implications for Oxygen in the Terrestrial Planets; Implications of Sulfur Isotopes for the Evolution of Atmospheric Oxygen; Oxygen in the Outer Solar System; and On the Oxidation States of the Galilean Satellites: Implications for Internal Structures.

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DOE OSTI2018

Collaborative Project: Ocean-Atmosphere Interaction From Meso- to Planetary-Scale: Mechanisms, Parameterization, and Variability

The project focused on the dynamics and scale dependence of the boundary layer response, the coupled responses in the Pacific, and low frequency oceanic processes. Using theory and model simulations, we found coupling of sea surface temperatures associated with the ocean eddy field and the atmospheric boundary layer be dependent on scale, and captured in wave-number space by transfer functions. Investigations of coupled processes focused on the sea surface temperatures scales of eastern boundary upwelling system, and showed stability and eddy variance in the Kuroshio Extension to be predictable with lead times of several years through ocean Rossby waves and coupling with the atmosphere. In addition to these dynamical processes, we found that a significant part of the ocean evolution is associated with density compensating temperature and salinity anomalies, that, unlike Rossby waves, behave like passive tracers and follow the mean circulation.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1984

Evolution of density in solar system ices

Pores present in ices in the solar system do not remain unchanged. In isothermal conditions they shrink, while in a thermal gradient they migrate towards the higher temperature and escape so that the ice densifies. This motion has been investigated for pure H2O- and CO2-ices in a very simple one-dimensional model assuming uniform thermal conductivity and temperature gradient. The results indicate that the densification of H2O-ice is so slow that it could be significant only for icy satellites having an internal heat source. On the other hand, CO2-ice densifies orders of magnitude faster and the effect should be important for the CO2 component of cometary nuclei. No effect is expected for icy planetary rings.

Smoluchowski, R.↗

NASA NTRS1998

Electron Thermalization in the Solar Wind and Planetary Plasma Boundaries

The work carried out under this contract attempts a better understanding of whistler wave generation and associated scattering of electrons in the solar wind. This task is accomplished through simulations using a particle-in-cell code and a Vlasov code. In addition, the work is supported by the utilization of a linear kinetic dispersion solver. Previously, we have concentrated on gaining a better understanding of the linear mode properties, and have tested the simulation codes within a known parameter regime. We are now in a new phase in which we implement, execute, and analyze production simulations. This phase is projected to last over several reporting periods, with this being the second cycle. In addition, we have started to research to what extent the evolution of the pertinent instabilities is two-dimensional. We are also continuing our work on the visualization aspects of the simulation results, and on a code version that runs on single-user Alpha-processor based workstations.

Krauss-Varban, Dietmar↗

NASA NTRS2005

Lunar and Planetary Science XXXVI, Part 17

The following topics were discussed: A Model for the Formation of Paterae on Io; LIBS-based Detection of As, Br, C, Cl, P, and S in the VUV Spectral Region in a Mars Atmosphere; Mass Independent Sulfur in Achondrites: Possible Evidence of Photochemistry in the Solar Nebula; Grain Size-dependent Viscosity and Oceans in Icy Satellites; Claritas Paleolake Studied from the MEX HRSC Data; Mars Express HRSC Colors of White Rock, Arabia, Mars; Lava and Flows of the Arcadia Region of Mars; Isotopic Composition of Lunar Soils and the Early Differentiation of the Moon; Trace Element Analysis of Lunar Soils by ICP-MS; Highly Siderophile Elements and Osmium Isotope Systematics in Ureilites: Are the Carbonaceous Veins Primary Components?; Evaporative Evolution of Martian Brines Based on Halogens in Nakhlites and MER Samples; Io from High-Resolution Galileo PPR Data Taken Simultaneously with SSI or NIMS Observations; Loki, Io: Groundbased Observations and a Model for Periodic Overturn; Deconstructing a Few Myths in the Interpretation of Satellite-Altitude Crustal Magnetic Field: Examples from Mars Global Surveyor; Semi-Autonomous Rover Operations: A Mars Technology Program Demonstration; Rotational Studies of Asteroids with Small Telescopes; Mineralogy and Temperature-induced Spectral Investigations of A-type Asteroids 246 Asporina and 446 Aeternitas; and Thermal History Calculations Versus Full Convection Models: Application to the Thermal Evolution of Mercury. Recent Solar-Proton Fluxes

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NASA NTRS2023

Chromium on Mercury: New Results From the MESSENGER X-Ray Spectrometer and Implications for the Innermost Planet’s Geochemical Evolution

Mercury, the innermost planet, formed under highly reduced conditions, based mainly on surface Fe, S, and Si abundances determined from MESSENGER mission data. The minor element Cr may serve as an independent oxybarometer but only very limited Cr data have been previously reported for Mercury. We report Cr/Si abundances across Mercury's surface based on MESSENGER X-Ray Spectrometer data throughout the spacecraft's orbital mission. The heterogeneous Cr/Si ratio ranges from 3.6 × 10 -5 in the Caloris Basin to 0.0012 within the high-magnesium region, with an average southern hemisphere value of 0.0008 (corresponding to about 200 ppm Cr). Absolute Cr/Si values have systematic uncertainty of at least 30%, but relative variations are more robust. By combining experimental Cr partitioning data along with planetary differentiation modeling, we find that if Mercury formed with bulk chondritic Cr/Al, Cr must be present in the planet's core and differentiation must have occurred at log ƒO 2 in the range of IW-6.5 to IW-2.5 in the absence of sulfides in its interior and a range of IW-5.5 to IW-2 with an FeS layer at the core-mantle boundary. Models with large fractions of Mg-Ca-rich sulfides in Mercury's interior are more compatible with moderately reducing conditions (IW-5.5 to IW-4) owing to the instability of Mg-Ca-rich sulfides at elevated ƒO 2 . These results indicate that if Mercury differentiated at a log ƒO 2 lower than IW-5.5, the presence of sulfides whether in the form of a FeS layer at the top of the core or Mg-Ca-rich sulfides within the mantle would be unlikely.

Larry R. Nittler↗

DOE OSTI2016

ORBITAL STABILITY OF MULTI-PLANET SYSTEMS: BEHAVIOR AT HIGH MASSES

In the coming years, high-contrast imaging surveys are expected to reveal the characteristics of the population of wide-orbit, massive, exoplanets. To date, a handful of wide planetary mass companions are known, but only one such multi-planet system has been discovered: HR 8799. For low mass planetary systems, multi-planet interactions play an important role in setting system architecture. In this paper, we explore the stability of these high mass, multi-planet systems. While empirical relationships exist that predict how system stability scales with planet spacing at low masses, we show that extrapolating to super-Jupiter masses can lead to up to an order of magnitude overestimate of stability for massive, tightly packed systems. We show that at both low and high planet masses, overlapping mean-motion resonances trigger chaotic orbital evolution, which leads to system instability. We attribute some of the difference in behavior as a function of mass to the increasing importance of second order resonances at high planet–star mass ratios. We use our tailored high mass planet results to estimate the maximum number of planets that might reside in double component debris disk systems, whose gaps may indicate the presence of massive bodies.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2004

Lunar and Planetary Science XXXV: Mars Tectonism and Volcanism

The session "Mars Tectonism and Volcanism", included the following reports:Structural Attitudes of Large Scale Layering in Valles Marineris, Mars, Calculated from Mars Orbiter Laser Altimeter Data and Mars Orbiter Camera Imagery; Stratigraphy of Eastern Coprates Chasma, Mars; Temporal Variability in Tharsis Stress State Based on Wrinkle Ridges and Strike-Slip Faulting; State of Stress in the Martian Lithosphere; Displacement-Length Scaling of Faults on Earth, Mars, and Beyond; Topographic Analysis of Quasi-Circular Depressions Around the Utopia Basin, Mars; The Olympus Mons Aureole Deposits: New Evidence for a Flank-failure Origin; Cerberus Fossae and Elysium Planitia Lavas, Mars: Source Vents, Flow Rates, Edifice Styles and Water Interactions; and Topographic Evidence for Eruptive Style Changes and Magma Evolution of Small Plains.

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DOE OSTI2015

TRANSIENT CHAOS AND FRACTAL STRUCTURES IN PLANETARY FEEDING ZONES

The circular restricted three-body problem is investigated in the context of accretion and scattering processes. In our model, a large number of identical non-interacting mass-less planetesimals are considered in the planar case orbiting a star-planet system. This description allows us to investigate the gravitational scattering and possible capture of the particles by the forming planetary embryo in a dynamical systems approach. Although the problem serves a large variety of complex motions, the results can be easily interpreted because of the low dimensionality of the phase space. We show that initial conditions define isolated regions of the disk, where planetesimals accrete or escape, which have, in fact, a fractal structure. The fractal geometry of these ''basins'' implies that the dynamics is very complex. Based on the calculated escape rates and escape times, it is also demonstrated that the planetary accretion rate is exponential for short times and follows a power law for longer integration. A new numerical calculation of the maximum mass that a planet can reach (described by the expression of the isolation mass) is also derived.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2016

Cupid's Arrow: An Innovative Nanosat to Sample Venus' Upper Atmosphere

In NASA's Discovery 2014 AO, the opportunity to propose a Technology Demonstration Opportunity (TDO) to enhance the primary mission was specified. For the Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy (VERITAS) mission, we elected to include the Cupid's Arrow nanosat TDO to sample and measure the abundances of noble gases and their isotopic ratios in Venus's upper atmosphere below the homopause. This paper will provide a basic overview of the VERITAS mission, with a focus on the Cupid's Arrow concept including a description of the mission, spacecraft design, and JPL's quadrupole ion trap mass spectrometer (QITMS) instrument specifications and design. In previous planetary entry probe mission designs, particularly at Venus, engineers w ere focused on entry and descent. A landed probe was also proposed for the New Frontiers SAGE mission. For Cupid's Arrow, the nanosat is designed to skim through the upper atmosphere, just below the homopause, in order to sample the atmosphere, perform the analysis, and then exit the atmosphere to transmit its data to the orbiting VERITAS spacecraft. Cupid's Arrow is a compelling addition to the VERITAS geology mission. A key missing link in our understanding of Venus' evolution is the noble gas abundances and their isotopic ratios. Not since Pioneer Venus have these measurements been made in the Venus atmosphere and never in the upper atmosphere, just below the homopause, to the degree of accuracy that will be accomplished by VERITAS' Cupid's Arrow nanosat.Such measurements were ranked as the number 1 investigation of the number 1 objective of the goal "Atmospheric Formation, Evolution, and Climate History ".

Discovery↗

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