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NASA NTRS2014

ANSMET 2013

From December 2013 to January 2014, MSFC Planetary Scientist Dr. Barbara Cohen participated in the Antarctic Search for Meteorites (ANSMET) 2013-2014 season. With a team of eight, a systematic search of the Antarctic ice in the South Miller Range turned up 333 samples; one of the largest is seen here with Dr. Cohen for scale. Since 1976, ANSMET has recovered more than 25,000 specimens from the ice along the Transantarctic Mountains. The icy surfaces of this area are particularly well suited for meteorite searches because of surface stranding: the surfaces must have bare ice, must be composed of large volumes, and the ice must flow out of the area more slowly than new ice arrives. The ANSMET specimens are currently the only reliable, continuous source of new, nonmicroscopic extraterrestrial material, and will continue to be until planetary sample-return missions are successful. The ANSMET program is supported by grants from the Solar System Exploration Division of NASA. Polar logistics are provided by the Office of Polar Programs of the U.S. National Science Foundation. The Principal Investigator of the current grant is Dr. Ralph P. Harvey at Case Western Reserve University. Dr. Barbara Cohen is seen with a large meteorite from the Antarctic's Miller Range

Adams, Mitzi L.↗

NASA NTRS2003

An Examination of Issues Related to a Europa Subsurface Component for the JIMO Mission

The Galileo Europa data set served to revolutionize our view of Europa. In particular the strong evidence of a large, cold, salty Ocean beneath 5-30 km of ice has profoundly altered the significance of Europa in our thinking, especially of context of habitability in the solar system. While much remains to be learned from spacecraft observations of several sorts, there are significant questions answerable only by in-situ techniques; these relate to the formation of Europa, the nature of its ocean, and the prospects for life in its ocean, sediments, and ice. We feel that wide-ranging discussion of an in-situ subsurface mission to Europa, as part of JIMO, should proceed. The science objective of the mission is to characterize the icy shell of Europa to resolve its provenance, estimate the composition of brine of the Europa ocean, and search for evidence of Earth-like life. Probably anyone would agree that an in-situ mission to Europa would be of great value, but he or she would also immediately take the position that such a mission is utterly impractical. We take the position here of defining the least complex mission that can nonetheless justify its cost and to argue that such a mission is realistic enough that it should be seriously considered. Our mission thinking has been: 1) Soft landing. A soft lander is required on a site sufficiently flat to offer a stable platform; no further site selectivity is required. 2) Subsurface exploration. The Europa subsurface must be examined. Surficial processes on Europa arguably have exposed the upper 200 m of shell to chemical effects from the Jovian radiation belts as well as cometary infall, etc; to examine native ice we must descend below that point to, for discussion, 300 m. At that depth we argue that the ice is characteristic of ice at depth and possibly is effectively sea ice. 3) Science data. A few simple measurements at various depths and at 300 m constitute a scientifically successful mission. Measurements would include analysis of meltwater for a few inorganic ions and amino acids and an optical examination of the borehole wall. 4) Communication. Transmission of data to an orbiter is essential, but we will constrain the landed mission to a daily communication over a few days. 5) Subsurface access. Drilling to 300 m is a significant challenge; it can be addressed by several means: Thermal Probe (Cryobot) which permits water to refreeze above the vehicle. This is our tentative choice with plutonium as the fuel to generate thermal energy for drilling and electrical power for operations. Open Hole Drill, a thermal system in which the meltwater is removed for greater thermal efficiency. Meltwater removal on Europa is both a complexity and a risk, but analysis is improved. Mechanical Drilling in which cutting or grinding generates ice chips which are removed. This is too complex at Europa temperatures. The measurement objectives for the mission will be: Obj. 1: Determine the concentration of simple inorganic salts in the Europa Ice Shell and, by extrapolation, of the ocean. These data will also validate spaceborne sensors. Obj. 2: Determine the nature and abundance of amino acids in the ice such that cometary infall material in the upper ice can be compared to material at depth. Obj. 3: Optically examine the ice to resolve inclusion structure, particulate content, and stratification. Access to 300 m depth is a significant if not audacious plan; we are aware that this has not been done on any planetary body. Our approach is the use of a plutonium heat source; to overcome Europa's surface temperature and to melt ice a significant amount of plutonium is needed, and significant shielding and other protective steps will be required. The quantity of plutonium is a key concern. The mission will require subsurface collection and processing of samples for in situ analysis, calling for a miniature, high pressure micro-sampling system designed to meet needs of instruments that require low presses for operation. The inlet system itself collects a micro-sample in the external high pressure environment, then transfers it into a protected low pressure environment for analysis.

Carsey, F. D.↗

NASA NTRS2005

Neptune Polar Orbiter with Probes

The giant planets of the outer solar system divide into two distinct classes: the gas giants Jupiter and Saturn, which consist mainly of hydrogen and helium; and the ice giants Uranus and Neptune, which are believed to contain significant amounts of the heavier elements oxygen, nitrogen, and carbon and sulfur. Detailed comparisons of the internal structures and compositions of the gas giants with those of the ice giants will yield valuable insights into the processes that formed the solar system and, perhaps, other planetary systems. By 2012, Galileo, Cassini and possibly a Jupiter Orbiter mission with microwave radiometers, Juno, in the New Frontiers program, will have yielded significant information on the chemical and physical properties of Jupiter and Saturn. A Neptune Orbiter with Probes (NOP) mission would deliver the corresponding key data for an ice giant planet. Such a mission would ideally study the deep Neptune atmosphere to pressures approaching and possibly exceeding 1000 bars, as well as the rings, Triton, Nereid, and Neptune s other icy satellites. A potential source of power would be nuclear electric propulsion (NEP). Such an ambitious mission requires that a number of technical issues be investigated, however, including: (1) atmospheric entry probe thermal protection system (TPS) design, (2) probe structural design including seals, windows, penetrations and pressure vessel, (3) digital, RF subsystem, and overall communication link design for long term operation in the very extreme environment of Neptune's deep atmosphere, (4) trajectory design allowing probe release on a trajectory to impact Neptune while allowing the spacecraft to achieve a polar orbit of Neptune, (5) and finally the suite of science instruments enabled by the probe technology to explore the depths of the Neptune atmosphere. Another driving factor in the design of the Orbiter and Probes is the necessity to maintain a fully operational flight system during the lengthy transit time from launch through Neptune encounter, and throughout the mission. Following our response to the recent NASA Research Announcement (NRA) for Space Science Vision Missions for mission studies by NASA for implementation in the 2013 or later time frame, our team has been selected to explore the feasibility of such a Neptune mission.

Bienstock, Bernard↗

NASA NTRS2012

Arctic PBL Cloud Height and Motion Retrievals from MISR and MINX

How Arctic clouds respond and feedback to sea ice loss is key to understanding of the rapid climate change seen in the polar region. As more open water becomes available in the Arctic Ocean, cold air outbreaks (aka. off-ice flow from polar lows) produce a vast sheet of roll clouds in the planetary boundary layer (PBl). The cold air temperature and wind velocity are the critical parameters to determine and understand the PBl structure formed under these roll clouds. It has been challenging for nadir visible/IR sensors to detect Arctic clouds due to lack of contrast between clouds and snowy/icy surfaces. In addition) PBl temperature inversion creates a further problem for IR sensors to relate cloud top temperature to cloud top height. Here we explore a new method with the Multiangle Imaging Spectro-Radiometer (MISR) instrument to measure cloud height and motion over the Arctic Ocean. Employing a stereoscopic-technique, MISR is able to measure cloud top height accurately and distinguish between clouds and snowy/icy surfaces with the measured height. We will use the MISR INteractive eXplorer (MINX) to quantify roll cloud dynamics during cold-air outbreak events and characterize PBl structures over water and over sea ice.

Wu, Dong L.↗

NASA NTRS1991

Flow and fracture of ice and ice mixtures

Frozen volatiles make up an important volume fraction of the low density moons of the outer solar system. Understanding the tectonic history of the surfaces of these moons, as well as the evolution of their interiors, requires knowledge of the mechanical strength of these icy materials under the appropriate planetary conditions (temperature, hydrostatic pressure, strain rate). Ongoing lab research is being conducted to measure mechanical properties of several different ices under conditions that faithfully reproduce condition both at the moons' surfaces (generally low temperature, to about 100 K, and low pressures) and in the deep interiors (warmer temperatures, pressures to thousands of atmospheres). Recent progress is reported in two different phases of the work: rheology of ices in the NH3-H2O system at temperatures and strain rates lower than ever before explored, with application to the ammonia-rich moons of Saturn and Uranus; and the water ice I yields II phase transformation, which not only applies directly to process deep in the interiors of Ganymede and Callisto, but holds implications for deep terrestrial earthquakes as well.

Durham, W. B.↗

NASA NTRS1984

Condensed matter physics of planets - Puzzles, progress and predictions

Attention is given to some of the major unresolved issues concerned with the physics of planetary interiors. The important advances in observations, and experimental and theoretical investigations are briefly reviewed, and some areas for further study are identified, including: the characteristics of atomic and electronic degrees of freedom at the high pressures and temperatures typical of a condensed planetary core; the behavior of water at megabar pressures; and the nature of the core-alloy in the earth and in the core mantle phase boundary. Consideration is also given to the behavior of carbon at high pressures and temperatures in the presence of oxygen and hydrogen; the behavior of the volatile ice assemblage in Titan at pressures of 2-40 kbar; and the electrical conductivities of matter under planetary core conditions.

Stevenson, D. J.↗

NASA NTRSDate not supplied

Aerosciences Implications for Uranus Aerocapture

Exploration of Uranus has been indicated as the highest priority new flagship planetary science missions for NASA in the 2022 Decadal Survey. Due to Uranus’ location as the second furthest planet from the Sun, interplanetary flight times of a traditional propulsive-capture orbiter can expect to take 13-15 years to reach Uranus while requiring up to two-thirds of the launch mass budget to be allocated to propellant alone. Aerocapture presents an alternative means to capture orbit around Uranus by using aerodynamic forces generated from flight through the planetary atmosphere to decelerate to orbital insertion while reducing time in interplanetary transit time and increasing on-orbit payload mass. To date, only one spacecraft (Voyager 2) has visited Uranus, and there have been no missions which have entered its atmosphere. While knowledge of planetary entry at rocky terrestrial planets with Air (N2/O2) and CO2 dominated atmospheres has greatly advanced over the past decades with a variety of missions to learn from, the H2/He composition and much larger atmosphere of ice giants such as Uranus poses new aerosciences implications which are not fully understood. These implications must be better understood not only for aerocapture, but for planetary entry at Uranus as a whole (such as a Uranus probe, as proposed by the 2022 Decadal Survey), as well as other ice giants like Neptune. To conduct a proper analysis of aerocapture methods, aerodynamic and aerothermal analysis of flight trajectories in Uranus atmosphere are required. Previous work has investigated aerocapture at Neptune (with similar atmosphere to Uranus) using a Mid-L/D configuration. Additional previous work considers the convective heating experienced in H2/He atmospheres. The current work looks to use heritage Low-L/D configurations, adding technical depth and maturation to analysis previously performed by Girija. Atmospheric flight at ice giants presents unique challenges, including but not limited to: fidelity of atmospheric models, large entry velocities due to location in the solar system, extended flight in rarefied flow conditions due to atmospheric scale, and unusual aerodynamic flow properties specific to Uranus and Ice Giant atmospheres.

Eli Shellabarger↗

NASA NTRS1969

Theoretical spectral scattering of ice clouds in the near infrared.

Ice clouds near IR spectral reflectivity dependence on particle size, noting application to planetary atmospheres

Cheyney, H.↗

NASA NTRS1993

GCM simulations of volcanic aerosol forcing. I - Climate changes induced by steady-state perturbations

The response of the climate system to a temporally and spatially constant amount of volcanic particles is simulated using a general circulation model (GCM). The optical depth of the aerosols is chosen so as to produce approximately the same amount of forcing as results from doubling the present CO2 content of the atmosphere and from the boundary conditions associated with the peak of the last ice age. The climate changes produced by long-term volcanic aerosol forcing are obtained by differencing this simulation and one made for the present climate with no volcanic aerosol forcing. The simulations indicate that a significant cooling of the troposphere and surface can occur at times of closely spaced multiple sulfur-rich volcanic explosions that span time scales of decades to centuries. The steady-state climate response to volcanic forcing includes a large expansion of sea ice, especially in the Southern Hemisphere; a resultant large increase in surface and planetary albedo at high latitudes; and sizable changes in the annually and zonally averaged air temperature.

Pollack, James B.↗

NASA NTRS2019

Voyager 2 Constraints on Plasmoid‐based Transport at Uranus

A magnetosphere controls a planet's evolution by suppressing or enhancing atmospheric loss to space. In situ measurements of Uranus' magnetosphere from the Voyager 2 flyby in 1986 provide the only direct evidence of magnetospheric transport processes responsible for this atmospheric escape at Uranus. Analysis of high‐resolution Voyager 2 magnetic field data in Uranus' magnetotail reveals the presence of a loop‐like plasmoid filled with planetary plasma traveling away from the planet. This first plasmoid observation in an Ice Giant magnetosphere elucidates that (1) both internal and external forces play a role in Uranus' magnetospheric dynamics, (2) magnetic reconnection contributes to the circulation of plasma and magnetic flux at Uranus, and (3) plasmoids may be a dominant transport mechanism for mass loss through Uranus' magnetotail.

DiBraccio, Gina A.↗

NASA NTRS2019

Voyager 2 Constraints on Plasmoid-Based Transport at Uranus

Gina A Dibraccio↗

NASA NTRS1988

Research in planetary astronomy and operation of the Mauna Kea Observatory

Spectroscopic studies with ground-based telescopes at low resolution can give compositional information of the surfaces and atmospheres of planets, satellites, asteroids, and comets. Solid state absorptions in ices and minerals are measurable by the low-resolution spectrophotometric technique. This program includes spectroscopy of distant comets, asteroids of particular interest in various contexts (planet crossers, outer main belt, trojans, etc.), Pluto and Charon, and planetary satellites of particular interest (Iapetus, Io, Uranian satellites, etc.). In the case of planets, satellites, and comets, emphasis is placed on volatiles (ices and organics), while for asteroids the stress is on mineralogy and the connection with the meteorites. New spectra show that the IR signature of Triton has changed since 1980, in that the methane bands are significantly weaker. Spectral evidence for the presence of molecular nitrogen remains convincing. Also, the brightness of Triton throughout its orbital cycle was measured to higher precision than before and was found to be constant to better than 0.02 mag. Suggestive spectral evidence was found for the presence of the C-H stretching mode band in diffuse reflection on asteroid 130 Elektra.

Cruikshank, Dale P.↗

NASA NTRS1974

Optical properties of particles in planetary atmospheres - Laboratory studies

The laboratory techniques employed for the determination of optical constants are discussed briefly. The values obtained for the real n and imaginary k parts of the refractive indices of water, ice, and liquid ammonia are presented graphically. Work currently in progress on solid ammonia and on sulphuric acid is discussed. Other approaches to studies of the properties of aerosols in planetary atmospheres are presented briefly.

Williams, D.↗

NASA NTRS2017

Characterize Planetary Surfaces from a Single Point to a Large Area Using a Standoff Ultra-Compact µ-Raman Instrument

A standoff Ultra-Compact micro-Raman (SUCR) instrument is used for detection of minerals, organic, and biological materials in daylight and nighttime conditions. The standoff measurements from a SUCR instrument based on micro-Raman spectroscopy on a rover or lander platform is ideal for identifying various types of ices, minerals, organics and biogenic materials. The μ-Raman measurements can assist in determining the biological potential for habitability assessment of planetary bodies as well as amino acid detection for evidence of past or present life on Mars, Europa, and other solar bodies. The SUCR instrument is used to inspect minerals, organic, biomarkers, ice, and embedded materials inside ice, as well as to conduct Raman line scanning from a single point to a large area for standoff detection at a 6-cm target distance.

M Nurul Abedin↗

NASA NTRS1990

Proceedings of a Workshop on Antarctic Meteorite Stranding Surfaces

The discovery of large numbers of meteorites on the Antarctic Ice Sheet is one of the most exciting developments in polar science in recent years. The meteorites are found on areas of ice called stranding surfaces. Because of the sudden availability of hundreds, and then thousands, of new meteorite specimens at these sites, the significance of the discovery of meteorite stranding surfaces in Antarctica had an immediate and profound impact on planetary science, but there is also in this discovery an enormous, largely unrealized potential to glaciology for records of climatic and ice sheet changes. The glaciological interest derives from the antiquity of the ice in meteorite stranding surfaces. This exposed ice covers a range of ages, probably between zero and more than 500,000 years. The Workshop on Antarctic Meteorite Stranding Surfaces was convened to explore this potential and to devise a course of action that could be recommended to granting agencies. The workshop recognized three prime functions of meteorite stranding surfaces. They provide: (1) A proxy record of climatic change (i.e., a long record of climatic change is probably preserved in the exposed ice stratigraphy); (2) A proxy record of ice volume change; and (3) A source of unique nonterrestrial material.

Cassidy, W. A.↗

NASA NTRS2014

Northern Late Winter Planetary Waves: MRO/MARCI Observations and Mars Climate Model Simulations

As does Earth, Mars presents pronounced global atmospheric circulation patterns. Solar differential heating drives mean meridional overturning (Hadley) circulations which are deep and intense, are hemispherically asymmetric, and where a cross-equatorial single cell dominates. Within middle and high latitudes, thermally indirect eddy-driven (Ferrel) circulation cells have been indicated. Differently, however, large-amplitude orography on planetary and continental scales on Mars can force very non-Earth-like hemispheric circulation patterns. Recent observations from the Mars Reconnaissance Orbiter, "Mars Color Imager" (MARCI) instrument are utilized that emphasize water ice clouds in ultra-violet (UV) wavelengths, and these measurements have been binned into "daily global maps" (DGMs) of water-ice cloud optical depth. The presence of large-scale, extratropical quasi-stationary atmospheric wave disturbances in middle and late winter of the northern hemisphere have been found to be present in such DGMs. In combination with such observations, a full-physics Mars global climate model (NASA ARC marsgcm 2.1) is applied to place the observations into context. During late northern winter, it is found that strong, forced Rossby modes (i.e., planetary waves) exist, and with direct correlation to columnintegrated cloud opacity undulating spatial patterns. At this season, zonal wavenumber s = 2 dominates (in contrast to wavenumber s = 1), consistent with MGS/TES analyses at this particular season (Banfield et al., 2003). Large-scale, planetary waves dictate the "coherence" of the northern polar vortex. Fundamentally, such forced planetary waves influence the polar vortex's impermeability (wave-induced) to tracer transport (e.g., dust and water-ice aerosol) and temporal mean water vapor spatial variations. The large-scale dynamical features of such planetary waves will be highlighted and discussed.

Northern polar vortex↗

NASA NTRS2020

The Radiation Stability of Thymine in Solid H2O

Nucleobases are of significant importance to all known organisms, may be an important building block of life, and could be important biosignatures of current or past life. Given their potential significance to the field of astrobiology, it is important to understand the survival of these molecules when subjected to ionizing radiation as is present in a range of extraterrestrial environments. In this work we present data on the kinetics of the radiolytic destruction of pure thymine, and water + thymine ice mixtures at temperatures from 13 to 150 K. Rate constants were measured using in situ infrared spectroscopy and radiolytic half-lives for thymine were computed for different planetary and interstellar environments. Our results demonstrate that the survival of thymine decreases as the dilution of thymine in water increases. Additionally, we find that thymine survival increases with ice temperature and that this decrease may be related to structure of the ice matrix.

nucleobases, radiolysis, astrobiology↗

NASA NTRS2019

Simulated Phase-dependent Spectra of Terrestrial Aquaplanets in M Dwarf Systems

Orbital phase-dependent variations in thermal emission and reflected stellar energy spectra can provide meaningful constraints on the climate states of terrestrial extrasolar planets orbiting M dwarf stars. Spatial distributions of water vapor, clouds, and surface ice are controlled by climate. In turn, water, in each of its thermodynamic phases, imposes significant modulations to thermal and reflected planetary spectra. Here we explore these characteristic spectral signals, based on 3D climate simulations of Earth-sized aquaplanets orbiting M dwarf stars near the habitable zone. By using 3D models, we can self-consistently predict surface temperatures and the location ofwater vapor, clouds, and surface ice in the climate system. Habitable zone planets in M dwarf systems are expected to be in synchronous rotation with their host star and thus present distinct differences in emitted and reflected energy fluxes depending on the observed hemisphere. Here we illustrate that icy, temperate, and incipient runaway greenhouse climate states exhibit phase-dependent spectral signals that enable their characterization.

Wolf, E. T.↗