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NASA NTRS2000

Reflectron Time-of-Flight Mass Spectrometer (REMAS) Instrumentation

The restricted mass and power budgets of landed science missions present a challenge to obtaining detailed analyses of planetary bodies. In situ studies, whether alone or as reconnaissance for sample return, must rely on highly miniaturized and autonomous instrumentation. Such devices must still produce useful data sets from a minimum of measurements. The great desire to understand the surfaces and interiors of planets, moons, and small bodies had driven the development of small, robotic techniques with ever-increasing capabilities. One of the most important goals on a surface mission is to study composition in many geological contexts. The mineralogical, molecular, elemental, and isotopic content of near-surface materials (regolith, rocks, soils, dust, etc.) at a variety of sites can complement broader imaging to describe the makeup and formative history of the body in question. Instruments that perform this site-to-site analysis must be highly transportable and work as a suite. For instance, a camera, microscope, spectrophotometer, and mass spectrometer can share several components and operate under a parallel command structure. Efficient use of multiple systems on a small rover has been demonstrated on the Mars Pathfinder mission.

Brinckerhoff, W. B.↗

NASA NTRS2004

Identifying Organic Molecules in Space: The AstroBiology Explorer (ABE) Mission Concept

The AstroBiology Explorer (ABE) mission concept consists of a modest dedicated space observatory having a 60 cm class primary mirror cooled to T less than 50 K equipped with medium resolution cross-dispersed spectrometers having cooled large format near- and mid-infrared detector arrays. Such a system would be capable of addressing outstanding problems in Astrochemistry and Astrophysics that are particularly relevant to Astrobiology and addressable via astronomical observation. The mission's observaticxiai program woiild make fundamental scieztific: prngress in establishing the nature, distribution, formation and evolution of organic and other molecular materials in the following extra-terrestrial environments: 1) The Outflow of Dying Stars; 2) The Diffuse Interstellar Medium (DISM); 3) Dense Molecular Clouds, Star Formation Regions, and Young Stellar/Planetary Systems; 4) Planets, Satellites, and Small Bodies within the Solar System; and 5) The Interstellar Media of Other Galaxies ABE could make fundamental progress in all of these area by conducting a 1 to 2 year mission to obtain a coordinated set of infrared spectroscopic observations over the 2.5 - 20 micron spectral range at a spectral resolution of R greater than 2500 of about 1500 galaxies, stars, planetary nebulae, young stellar objects, and solar system objects.

Ennico, Kimberly↗

NASA NTRS2004

Developing Architectures and Technologies for an Evolvable NASA Space Communication Infrastructure

Space communications architecture concepts play a key role in the development and deployment of NASA's future exploration and science missions. Once a mission is deployed, the communication link to the user needs to provide maximum information delivery and flexibility to handle the expected large and complex data sets and to enable direct interaction with the spacecraft and experiments. In human and robotic missions, communication systems need to offer maximum reliability with robust two-way links for software uploads and virtual interactions. Identifying the capabilities to cost effectively meet the demanding space communication needs of 21st century missions, proper formulation of the requirements for these missions, and identifying the early technology developments that will be needed can only be resolved with architecture design. This paper will describe the development of evolvable space communication architecture models and the technologies needed to support Earth sensor web and collaborative observation formation missions; robotic scientific missions for detailed investigation of planets, moons, and small bodies in the solar system; human missions for exploration of the Moon, Mars, Ganymede, Callisto, and asteroids; human settlements in space, on the Moon, and on Mars; and great in-space observatories for observing other star systems and the universe. The resulting architectures will enable the reliable, multipoint, high data rate capabilities needed on demand to provide continuous, maximum coverage of areas of concentrated activities, such as in the vicinity of outposts in-space, on the Moon or on Mars.

Bhasin, Kul↗

NASA NTRS2004

Identifying Organic Molecules in Space: The AstroBiology Explorer (ABE) Mission Concept

The AstroBiology Explorer (ABE) mission concept consists of a dedicated space observatory having a 60 cm class primary mirror cooled to T < 50 K equipped with medium resolution cross-dispersed spectrometers having cooled large format near- and mid-infrared detector arrays. Such a system would be capable of addressing outstanding problems in Astrochemistry and Astrophysics that are particularly relevant to Astrobiology and addressable via astronomical observation. The mission s observational program would make fundamental scientific progress in establishing the nature, distribution, formation and evolution of organic and other molecular materials in the following extra-terrestrial environments: 1) The Outflow of Dying Stars, 2) The Diffuse Interstellar Medium, 3) Dense Molecular Clouds, Star Formation Regions, and Young StellarPlanetary Systems, 4) Planets, Satellites, and Small Bodies within the Solar System, and 5 ) The Interstellar Media of Other Galaxies. ABE could make fundamental progress in all of these areas by conducting a 1 to 2 year mission to obtain a coordinated set of infrared spectroscopic observations over the 2.5-20 micron spectral range at a spectral resolution of R > 2000 of about 1500 objects including galaxies, stars, planetary nebulae, young stellar objects, and solar system objects. Keywords: Astrobiology, infrared, Explorers, interstellar organics, telescope, spectrometer, space, infrared detectors

Ennico, K. A.↗

NASA NTRS2011

Analysis of Mars Analogue Soil Samples Using Solid-Phase Microextraction, Organic Solvent Extraction and Gas Chromatography/Mass Spectrometry

Polycyclic aromatic hydrocarbons (PAHs) are robust and abundant molecules in extraterrestrial environments. They are found ubiquitously in the interstellar medium and have been identified in extracts of meteorites collected on Earth. PAHs are important target molecules for planetary exploration missions that investigate the organic inventory of planets, moons and small bodies. This study is part of an interdisciplinary preparation phase to search for organic molecules and life on Mars. We have investigated PAH compounds in desert soils to determine their composition, distribution and stability. Soil samples (Mars analogue soils) were collected at desert areas of Utah in the vicinity of the Mars Desert Research Station (MDRS), in the Arequipa region in Peru and from the Jutland region of Denmark. The aim of this study was to optimize the solid-phase microextraction (SPME) method for fast screening and determination of PAHs in soil samples. This method minimizes sample handling and preserves the chemical integrity of the sample. Complementary liquid extraction was used to obtain information on five- and six-ring PAH compounds. The measured concentrations of PAHs are, in general, very low, ranging from 1 to 60 ng g(sup -1). The texture of soils is mostly sandy loam with few samples being 100% silt. Collected soils are moderately basic with pH values of 8-9 except for the Salten Skov soil, which is slightly acidic. Although the diverse and variable microbial populations of the samples at the sample sites might have affected the levels and variety of PAHs detected, SPME appears to be a rapid, viable field sampling technique with implications for use on planetary missions.

Orzechowska, G. E.↗

NASA NTRS2012

Masses, Radii, and Cloud Properties of the HR 8799 Planets

The near-infrared colors of the planets directly imaged around the A star HR 8799 are much redder than most field brown dwarfs of the same effective temperature. Previous theoretical studies of these objects have compared the photometric and limited spectral data of the planets to the predictions of various atmosphere and evolution models and concluded that the atmospheres of planets b, c, and d are unusually cloudy or have unusual cloud properties. Most studies have also found that the inferred radii of some or all of the planets disagree with expectations of standard giant planet evolution models. Here we compare the available data to the predictions of our own set of atmospheric and evolution models that have been extensively tested against field L and T dwarfs, including the reddest L dwarfs. Unlike almost all previous studies we specify mutually self-consistent choices for effective temperature, gravity, cloud properties, and planetary radius. This procedure yields plausible and self-consistent values for the masses, effective temperatures, and cloud properties of all three planets. We find that the cloud properties of the HR 8799 planets are in fact not unusual but rather follow previously recognized trends including a gravity dependence on the temperature of the L to T spectral transition, some reasons for which we discuss. We find that the inferred mass of planet b is highly sensitive to the H and K band spectrum. Solutions for planets c and particularly d are less certain but are consistent with the generally accepted constraints on the age of the primary star and orbital dynamics. We also confirm that as for L and T dwarfs and solar system giant planets, non-equilibrium chemistry driven by atmospheric mixing is also important for these objects. Given the preponderance of data suggesting that the L to T spectral type transition is gravity dependent, we present a new evolution calculation that predicts cooling tracks on the near-infrared color-magnitude diagram. Finally we argue that the range of uncertainty conventionally quoted for the bolometric luminosity of all three planets is too small.

Marley, Mark S.↗

NASA NTRS2013

Trajectory Browser: An Online Tool for Interplanetary Trajectory Analysis and Visualization

The trajectory browser is a web-based tool developed at the NASA Ames Research Center for finding preliminary trajectories to planetary bodies and for providing relevant launch date, time-of-flight and (Delta)V requirements. The site hosts a database of transfer trajectories from Earth to planets and small-bodies for various types of missions such as rendezvous, sample return or flybys. A search engine allows the user to find trajectories meeting desired constraints on the launch window, mission duration and (Delta)V capability, while a trajectory viewer tool allows the visualization of the heliocentric trajectory and the detailed mission itinerary. The anticipated user base of this tool consists primarily of scientists and engineers designing interplanetary missions in the context of pre-phase A studies, particularly for performing accessibility surveys to large populations of small-bodies.

Foster, Cyrus James↗

NASA NTRS2017

Exospheric Escape: A Parametrical Study

The study of exospheres can help us understand the long-term loss of volatiles from planetary bodies due to interactions of planets, satellites, and small bodies with the interplanetary medium, solar radiation, and internal forces including diffusion and outgassing. Recent evidence for water and OH on the Moon has spurred interest in processes involving chemistry and sequestration of volatile species at the poles and in voids. In recent years, NASA has sent spacecraft to asteroids including Vesta and Ceres, and ESA sent Rosetta to comet 67P/Churyumov-Gerasimenko and the asteroids Lutetia and Steins. Japan's Hayabusa spacecraft returned a sample from asteroid Itakowa, and OSIRIS-REX will return a sample from a primitive asteroid, Bennu, to Earth. In a surface-bounded exosphere, the gases are derived from the surface and thus reflect the composition of the body's regolith, although not in a one-to-one ratio. Observation of an escaping exosphere, termed a corona, is challenging. We have therefore embarked on a parametrical study of exospheres as a function of mass of the exospheric species, mass of the primary body and source velocity distribution, specifically thermal (Maxwell-Boltzmann) and sputtering. The goal is to provide a quick look to determine under what conditions and for what mass of the primary body the species of interest are expected to be bound or escaping and to quickly estimate the observability of exospheric species. This work does not provide a comprehensive model but rather serves as a starting point for further study. These parameters will be useful for mission planning as well as for students beginning a study of planetary exospheres.

Volatilels↗

NASA NTRS2017

Exospheric Escape: A Parametrical Study

The study of exospheres can help us understand the long-term loss of volatiles from planetary bodies due to interactions of planets, satellites, and small bodies with the interplanetary medium, solar radiation, and internal forces including diffusion and outgassing. Recent evidence for water and OH on the Moon has spurred interest in processes involving chemistry and sequestration of volatile species at the poles and in voids. In recent years, NASA has sent spacecraft to asteroids including Vesta and Ceres, and ESA sent Rosetta to comet 67P/Churyumov–Gerasimenko and the asteroids Lutetia and Steins. Japan's Hayabusa spacecraft returned a sample from asteroid Itakowa, and OSIRIS-REX will return a sample from a primitive asteroid, Bennu, to Earth. In a surface-bounded exosphere, the gases are derived from the surface and thus reflect the composition of the body's regolith, although not in a one-to-one ratio. Observation of an escaping exosphere, termed a corona, is challenging. We have therefore embarked on a parametrical study of exospheres as a function of mass of the exospheric species, mass of the primary body and source velocity distribution, specifically thermal (Maxwell-Boltzmann) and sputtering. The goal is to provide a quick look to determine under what conditions and for what mass of the primary body the species of interest are expected to be bound or escaping and to quickly estimate the observability of exospheric species. This work does not provide a comprehensive model but rather serves as a starting point for further study. These parameters will be useful for mission planning as well as for students beginning a study of planetary exospheres.

Exospheres↗

NASA NTRS2015

Mercury-T: A New Code to Study Tidally Evolving Multi-Planet Systems. Applications to Kepler-62

A large proportion of observed planetary systems contain several planets in a compact orbital configuration, and often harbor at least one close-in object. These systems are then most likely tidally evolving. We investigate how the effects of planet-planet interactions influence the tidal evolution of planets. We introduce for that purpose a new open-source addition to the Mercury N-body code, Mercury-T, which takes into account tides, general relativity and the effect of rotation-induced flattening in order to simulate the dynamical and tidal evolution of multi-planet systems. It uses a standard equilibrium tidal model, the constant time lag model. Besides, the evolution of the radius of several host bodies has been implemented (brown dwarfs, M-dwarfs of mass 0:1 M(sub ⨀), Sun-like stars, Jupiter). We validate the new code by comparing its output for one-planet systems to the secular equations results. We find that this code does respect the conservation of total angular momentum. We applied this new tool to the planetary system Kepler-62. We find that tides influence the stability of the system in some cases. We also show that while the four inner planets of the systems are likely to have slow rotation rates and small obliquities, the fifth planet could have a fast rotation rate and a high obliquity. This means that the two habitable zone planets of this system, Kepler-62e ad f are likely to have very different climate features, and this of course would influence their potential at hosting surface liquid water..

Dynamical evolution and stability↗

NASA NTRS1977

Infrared observations of the planets

Four areas in outer solar system research affected by IR observational findings are surveyed: the nature of comets, the structure of the atmospheres of the outer planets, the surface of small bodies present in the outer solar system, and the history of contraction of the outer planets. Advances in the study of the relation of cometary dust to interstellar material and to the surface material on outer solar system satellites, and of the connection between internal energies of the large planets and the properties of their satellites in terms of calculations of the contraction history of the large planets, are reported.

Rieke, G. H.↗

NASA NTRS2001

Meteoric Ions in Planetary Ionospheres

Solar system debris, in the form of meteoroids, impacts every planet. The flux, relative composition and speed of the debris at each planet depends on the planet's size and location in the solar system. Ablation in the atmosphere evaporates the meteoric material and leaves behind metal atoms. During the ablation process metallic ions are formed by impact ionization. For small inner solar system planets, including Earth, this source of ionization is typically small compared to either photoionization or charge exchange with ambient molecular ions. For Earth, the atmosphere above the main deposition region absorbs the spectral lines capable of ionizing the major metallic atoms (Fe and Mg) so that charge exchange with ambient ions is the dominant source. Within the carbon dioxide atmosphere of Mars (and possibly Venus), photoionization is important in determining the ion density. For a heavy planet like Jupiter, far from the sun, impact ionization of ablated neutral atoms by impacts with molecules becomes a prominent source of ionization due to the gravitational acceleration to high incident speeds. We will describe the processes and location and extent of metal ion layers for Mars, Earth and Jupiter, concentrating on flagging the uncertainties in the models at the present time. This is an important problem, because low altitude ionosphere layers for the planets, particularly at night, probably consist predominantly of metallic ions. Comparisons with Earth will be used to illustrate the differing processes in the three planetary atmospheres.

Pesnell, W. D.↗

NASA NTRS2017

Prospecting for Habitable Worlds

NASAs Kepler Mission was launched in March 2009 as NASAs first mission capable of finding Earth-size planets orbiting in the habitable zone of Sun-like stars, that range of distances for which liquid water would pool on the surface of a rocky planet. Kepler has discovered over 2200 planets and over 2200 candidate planets, many of them as small as the Earth. Forty nine of these are less than twice the size of Earth and orbit in the habitable zone of their stars, all of which are cooler and significantly smaller than the Sun.Today, Keplers amazing success seems to be a fait accompli to those unfamiliar with her history. But twenty years ago, there were no planets known outside our solar system, and few people believed it was possible to detect tiny Earth-size planets orbiting other stars. Indeed, demonstrating that the science was feasible took four proposals to NASAs Discovery Program and extensive research and laboratory demonstrations. Motivating NASA to select Kepler for launch required a confluence of the right detector technology, advances in signal processing and algorithms, and the power of supercomputing. On August 23 2015 we reported the discovery of Kepler-452b, the first small, possibly rocky planet in the habitable zone of a G2 star very similar to our own. Kepler-452b orbits its star once every 385 days in an orbit just 5 larger than that of Earth. This discovery represents an important step towards finding and characterizing small habitable worlds orbiting Sun-like stars.

Jenkins, Jon M.↗

NASA NTRS2016

The Sustainability of Habitability on Terrestrial Planets: Insights, Questions, and Needed Measurements from Mars for Understanding the Evolution of Earth-Like Worlds

What allows a planet to be both within a potentially habitable zone and sustain habitability over long geologic time? With the advent of exoplanetary astronomy and the ongoing discovery of terrestrial-type planets around other stars, our own solar system becomes a key testing ground for ideas about what factors control planetary evolution. Mars provides the solar systems longest record of the interplay of the physical and chemical processes relevant to habitability on an accessible rocky planet with an atmosphere and hydrosphere. Here we review current understanding and update the timeline of key processes in early Mars history. We then draw on knowledge of exoplanets and the other solar system terrestrial planets to identify six broad questions of high importance to the development and sustaining of habitability (unprioritized): (1) Is small planetary size fatal? (2) How do magnetic fields influence atmospheric evolution? (3) To what extent does starting composition dictate subsequent evolution, including redox processes and the availability of water and organics? (4) Does early impact bombardment have a net deleterious or beneficial influence? (5) How do planetary climates respond to stellar evolution, e.g., sustaining early liquid water in spite of a faint young Sun? (6) How important are the timescales of climate forcing and their dynamical drivers? Finally, we suggest crucial types of Mars measurements (unprioritized) to address these questions: (1) in situ petrology at multiple units/sites; (2) continued quantification of volatile reservoirs and new isotopic measurements of H, C, N, O, S, Cl, and noble gases in rocks that sample multiple stratigraphic sections; (3) radiometric age dating of units in stratigraphic sections and from key volcanic and impact units; (4) higher-resolution measurements of heat flux, subsurface structure, and magnetic field anomalies coupled with absolute age dating. Understanding the evolution of early Mars will feed forward to understanding the factors driving the divergent evolutionary paths of the Earth, Venus, and thousands of small rocky extra solar planets yet to be discovered.

rocky exoplanets↗

NASA NTRS1994

The symbiosis of photometry and radial-velocity measurements

The FRESIP mission is optimized to detect the inner planets of a planetary system. According to the current paradigm of planet formation, these planets will probably be small Earth-sized objects. Ground-based radial-velocity programs now have the sensitivity to detect Jovian-mass planets in orbit around bright solar-type stars. We expect the more massive planets to form in the outer regions of a proto-stellar nebula. These two types of measurements will very nicely complement each other, as they have highest detection probability for very different types of planets. The combination of FRESIP photometry and ground-based spectra will provide independent confirmation of the existence of planetary systems in orbit around other stars. Such detection of both terrestrial and Jovian planets in orbit around the same star is essential to test our understanding of planet formation.

Cochran, William D.↗

NASA NTRS2008

Taking the Measure of the Universe : Precision Astrometry with SIM PlanetQuest

Precision astrometry at microarcsecond accuracy has application to a wide range of astrophysical problems. This paper is a study of the science questions that can be addressed using an instrument with flexible scheduling that delivers parallaxes at about 4 microarcsec (microns)as) on targets as faint as V = 20, and differential accuracy of 0.6 (microns)as on bright targets. The science topics are drawn primarily from the Team Key Projects, selected in 2000, for the Space Interferometry Mission PlanetQuest (SIM PlanetQuest). We use the capabilities of this mission to illustrate the importance of the next level of astrometric precision in modern astrophysics. SIM PlanetQuest is currently in the detailed design phase, having completed in 2005 all of the enabling technologies needed for the flight instrument. It will be the first space-based long baseline Michelson interferometer designed for precision astrometry. SIM will contribute strongly to many astronomical fields including stellar and galactic astrophysics, planetary systems around nearby stars, and the study of quasar and AGN nuclei. Using differential astrometry SIM will search for planets with masses as small as an Earth orbiting in the 'habitable zone' around the nearest stars, and could discover many dozen if Earth-like planets are common. It will characterize the multiple-planet systems that are now known to exist, and it will be able to search for terrestrial planets around all of the candidate target stars in the Terrestrial Planet Finder and Darwin mission lists. It will be capable of detecting planets around young stars, thereby providing insights into how planetary systems are born and how they evolve with time. Precision astrometry allows the measurement of accurate dynamical masses for stars in binary systems. SIM will observe significant numbers of very high- and low-mass stars, providing stellar masses to 1%, the accuracy needed to challenge physical models. Using precision proper motion measurements, SIM will probe the Galactic mass distribution, and through studies of tidal tails, the formation and evolution of the Galactic halo. SIM will contribute to cosmology through improved accuracy of the Hubble Constant. With repeated astrometric measurements of the nuclei of active galaxies, SIM will probe the dynamics of accretion disks around supermassive black holes, and the relativistic jets that emerge from them.

Quasars and Active Galactic Nuclei↗

NASA NTRS2003

Formation of Giant Planets and Brown Dwarves

According to the prevailing core instability model, giant planets begin their growth by the accumulation of small solid bodies, as do terrestrial planets. However, unlike terrestrial planets, the growing giant planet cores become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. Models predict that rocky planets should form in orbit about most stars. It is uncertain whether or not gas giant planet formation is common, because most protoplanetary disks may dissipate before solid planetary cores can grow large enough to gravitationally trap substantial quantities of gas. Ongoing theoretical modeling of accretion of giant planet atmospheres, as well as observations of protoplanetary disks, will help decide this issue. Observations of extrasolar planets around main sequence stars can only provide a lower limit on giant planet formation frequency . This is because after giant planets form, gravitational interactions with material within the protoplanetary disk may cause them to migrat~ inwards and be lost to the central star. The core instability model can only produce planets greater than a few jovian masses within protoplanetary disks that are more viscous than most such disks are believed to be. Thus, few brown dwarves (objects massive enough to undergo substantial deuterium fusion, estimated to occur above approximately 13 jovian masses) are likely to be formed in this manner. Most brown dwarves, as well as an unknown number of free-floating objects of planetary mass, are probably formed as are stars, by the collapse of extended gas/dust clouds into more compact objects.

Lissauer, Jack J.↗

NASA NTRS1980

Structure and evolution of Uranus and Neptune

Three-layer interior models of Uranus and Neptune with central rocky cores, mantles of water, methane, and ammonia (the 'ices'), and outer envelopes primarily composed of hydrogen and helium are presented. The models incorporate a new H2O equation of state based on experimental data which is considerably 'softer' than previous H2O equations of state. Corrections for interior temperatures approximately 5000 K are included in the models, and the thermal evolution of both planets is investigated using recent heat flow measurements. It is found that the evolutionary considerations are consistent with gravitational field data in supporting models with approximately solar abundances of 'ice' and 'rock'. Evolutionary considerations indicate that initial temperatures and luminosities for Uranus and Neptune were not substantially higher than the present value. Both planets apparently have relatively small approximately 1-2 earth masses) hydrogen-helium envelopes, with Neptune's envelope smaller than Uranus'. A monotonic trend is evident among the Jovian planets: all have central rock-ice cores of approximately 15 earth masses, but with hydrogen-helium envelopes which decrease in mass from Jupiter to Saturn to Uranus to Neptune.

Hubbard, W. B.↗