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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Exo-C: a Probe-Scale Space Mission to Directly Image and Spectroscopically Characterize Exoplanetary Systems Using an Internal Coronagraph

"Exo-C" is NASA's first community study of a modest aperture space telescope designed for high contrast observations of exoplanetary systems. The mission will be capable of taking optical spectra of nearby exoplanets in reflected light, discover previously undetected planets, and imaging structure in a large sample of circumstellar disks. It will obtain unique science results on planets down to super-Earth sizes and serve as a technology pathfinder toward an eventual flagship-class mission to find and characterize habitable exoplanets. We present the mission/payload design and highlight steps to reduce mission cost/risk relative to previous mission concepts. At the study conclusion in 2015, NASA will evaluate it for potential development at the end of this decade. Keywords: Exoplanets, high contrast imaging, optical astronomy, space mission concepts

high contrast imaging↗
NASA NTRS2019

Exo-C: A Dedicated Probe-scale Space Mission for Coronagraphic Imaging and Spectroscopy of Exoplanetary Systems

"Exo-C", the Exoplanet Coronagraph, is a concept for a dedicated probe-scale (< $1B) space mission optimized for direct imaging of exoplanetary systems. It was the product of a detailed mission study carried in 2013-2015 under the sponsorship of the NASA Astrophysics Division. Exo-C was designed to be capable of spectrally characterizing 1-2 dozen nearby exoplanets in reflected visible light, discovering previously undetected planets, and imaging structure in hundreds of circumstellar disks. It would obtain unique science results on planets down to super-Earth size and serve as a technology pathfinder toward an eventual flagship-class mission to find and characterize habitable Earth-like exoplanets. Key design elements are an unobscured telescope aperture, an internal coronagraph with deformable mirrors for precise wavefront control, and an orbit and observatory design chosen for high thermal stability. ExoC’s telescope aperture, orbit, mission lifetime, and spacecraft bus are all comparable to those of the highly successful Kepler mission. Much of the needed technology development (precision pointing, wavefront sensing and correction, high contrast integral field spectroscopy, detector flight readiness) has been advanced by the WFIRST Coronagraph Instrument (CGI) project over the past several years. Mission performance, mass, power, and cost estimates have also benefited from detailed work by the WFIRST CGI team. A Cost and Technical Evaluation (CATE) was performed in 2015 by the Aerospace Corporation. Today Exo-C is a backup option to WFIRST CGI. It could nominally be implemented within seven years from project start. This white paper summarizes the study final report, with updates on performance and technical readiness as of spring 2019.

Karl R. Stapelfeldt↗
NASA NTRS2018

Space-Based Infrared Interferometry to Study Exoplanetary Atmospheres

The quest for other habitable worlds and the search for life among them are major goals of modern astronomy. One way to make progress towards these goals is to obtain high-quality spectra of a large number of exoplanets over a broad range of wavelengths. While concepts currently investigated in the United States are focused on visible/NIR wavelengths, where the planets are probed in reflected light, a compelling alternative to characterize planetary atmospheres is the mid-infrared waveband (5-20 um). Indeed, mid-infrared observations provide key information on the presence of an atmosphere, the surface conditions (e.g., temperature, pressure, habitability), and the atmospheric composition in important species such as H2O,CO2, O3, CH4, and N2O. This information is essential to investigate the potential habitability of exoplanets and to make progress towards the search for life in the Universe. Obtaining high-quality mid-infrared spectra of exoplanets from the ground is however extremely challenging due to the overwhelming brightness and turbulence of the Earth's atmosphere. In this paper, we present a concept of space-based midinfrared interferometer that can tackle this observing challenge and discuss the maintechnological developments required to launch such a sophisticated instrument.

Defrère, D.↗
NASA NTRS2000

'Hot Topics' in Astrophysics

Three current topics in astrophysics are described here on the occasion of the joint meeting of the American Association of Physics Teachers and the American Astronomical Society (Jan. 7-11, 2001, San Diego, Calif.). Many equally exciting topics--ranging from the dozens of newly discovered planets of sunlike stars to evidence suggesting that the expansion of the universe is accelerating--could have been chosen. The topics discussed are: (1) the habitability of Mars, (2) black holes, galaxy bulges, and the X-ray background, and (3) the greatest explosions since the Big Bang.

Maran, Stephen P.↗
NASA NTRS2018

Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life

In the coming years and decades, advanced space- and ground-based observatories will allow an unprecedented opportunity to probe the atmospheres and surfaces of potentially habitable exoplanets for signatures of life. Life on Earth, through its gaseous products and reflectance and scattering properties, has left its fingerprint on the spectrum of our planet. Aided by the universality of the laws of physics and chemistry, we turn to Earth's biosphere, both in the present and through geologic time, for analog signatures that will aid in the search for life elsewhere. Considering the insights gained from modern and ancient Earth, and the broader array of hypothetical exoplanet possibilities, we have compiled a comprehensive overview of our current understanding of potential exoplanet biosignatures, including gaseous, surface, and temporal biosignatures. We additionally survey biogenic spectral features that are well known in the specialist literature but have not yet been robustly vetted in the context of exoplanet biosignatures. We briefly review advances in assessing biosignature plausibility, including novel methods for determining chemical disequilibrium from remotely obtainable data and assessment tools for determining the minimum biomass required to maintain short-lived biogenic gases as atmospheric signatures. We focus particularly on advances made since the seminal review by Des Marais et al. The purpose of this work is not to propose new biosignature strategies, a goal left to companion articles in this series, but to review the current literature, draw meaningful connections between seemingly disparate areas, and clear the way for a path forward.

biosignatures↗
NASA NTRS2021

Spin-Orbit Variations, Greenhouse Gases, and Superhabitable Conditions on Terrestrial Worlds in Multi-Planet Systems

Heller and Armstrong (Astrobiology, 2014) describe a number of ways in which an Earth-like world (“Earth twins” with a tidal heat flux Ft less than 0.04 W/m2, and within their star’s habitable zone) might be “superhabitable,” with surface environments that are more amenable to life than the common benchmark of modern Earth. Over Earth history, several time periods are known from the geologic record that could meet these criteria, providing multiple opportunities to explore known superhabitable and inhabited planetary conditions from an astrophysical perspective.

Earth-like world↗
NASA NTRS2006

Linking Yellowstone Research to Mars Exploration

Yellowstone's hydrothermal features and their associated communities of thermophiles are studied by scientists who are searching for evidence of life on other planets. The connection is extreme environments. If life originated in the extreme conditions thought to have been widespread on ancient Earth, it may well have developed on other planets and it might still exist today. The chemosynthetic microbes that thrive in some of Yellowstone s hot springs do so by metabolizing inorganic chemicals, a source of energy that does not require sunlight. Such chemical energy sources provide the most likely habitable niches for life on Mars or on the moons of Jupiter-Ganymede, Europa, and Callisto-where uninhabitable surface conditions preclude photosynthesis. Chemical energy sources, along with extensive groundwater systems (such as on Mars) or oceans beneath icy crusts (such as Jupiter's moons) could provide habitats for life. The study of stromatolites on Earth may also be applied to the search for life on other planets. If stromatolites are eventually found in the rocks of Mars or on other planets, we will have proven that life once existed elsewhere in the universe. Yellowstone National Park will continue to be an important site for studies at the physical and chemical limits of survival. These studies will give scientists a better understanding of the conditions that give rise to and support life, and they will learn how to recognize signatures of life in ancient rocks and on distant planets.

DesMarais, David J.↗
NASA NTRS1985

The evolution of complex life

The emergence of complex living organisms in the context of evolutionary biology, planetary environments, and space events is investigated. The application of data on biological evolution, climatology, and the chemical and physical environments of the earth's surface, to explain the development of extraterrestrial life is described and an example is provided. The possibility of extraplanetary disturbances such as, meteorite and comet bombardments, and supernova explosions, causing the elimination of preexisting life and allowing advanced life development is analyzed. The possible existence of different life cycles (genetic and reproductive strategies) on other planets is studied. The GAIA hypothesis (Lovelock, 1979) which states living things modify the global environment to their own advantage is examined. The improved identification of habitable planetary environments and the possible existence of a form of extraterrestrial intelligent life is discussed.

Billingham, J.↗
NASA NTRS1996

Astrobiology Workshop: Leadership in Astrobiology

Astrobiology is defined in the 1996 NASA Strategic Plan as 'The study of the living universe.' At NASA's Ames Research Center, this endeavor encompasses the use of space to understand life's origin, evolution, and destiny in the universe. Life's origin refers to understanding the origin of life in the context of the origin and diversity of planetary systems. Life's evolution refers to understanding how living systems have adapted to Earth's changing environment, to the all-pervasive force of gravity, and how they may adapt to environments beyond Earth. Life's destiny refers to making long-term human presence in space a reality, and laying the foundation for understanding and managing changes in Earth's environment. The first Astrobiology Workshop brought together a diverse group of researchers to discuss the following general questions: Where and how are other habitable worlds formed? How does life originate? How have the Earth and its biosphere influenced each other over time? Can terrestrial life be sustained beyond our planet? How can we expand the human presence to Mars? The objectives of the Workshop included: discussing the scope of astrobiology, strengthening existing efforts for the study of life in the universe, identifying new cross-disciplinary programs with the greatest potential for scientific return, and suggesting steps needed to bring this program to reality. Ames has been assigned the lead role for astrobiology by NASA in recognition of its strong history of leadership in multidisciplinary research in the space, Earth, and life sciences and its pioneering work in studies of the living universe. This initial science workshop was established to lay the foundation for what is to become a national effort in astrobiology, with anticipated participation by the university community, other NASA centers, and other agencies. This workshop (the first meeting of its kind ever held) involved life, Earth, and space scientists in a truly interdisciplinary sharing of ideas related to life in the universe, and by all accounts was a resounding success.

DeVincenzi, D.↗
NASA NTRS2011

Astrobiology in the Field: Studying Mars by Analogue Expeditions on Earth

We will present a strategy for how one prepares to engage in fieldwork on another planets by practicing in analogous environments on the Earth, including at Mono Lake. As an example, we will address the problem of how to study the habitability of an environment when you have no idea what kind of life might be there to exploit it. This will all be related to the upcoming launch of the Mars Science Laboratory to Mars in late November this year.

Conrad, Pamela G.↗
NASA NTRS2014

The Earth is a Planet Too!

When the solar system formed, the sun was 30 dimmer than today and Venus had an ocean. As the sun brightened, a runaway greenhouse effect caused the Venus ocean to boil away. At times when Earth was younger, the sun less bright, and atmospheric CO2 less, Earth froze over (snowball Earth). Earth is in the sweet spot today. Venus is closer to sun than Earth is, but cloud-covered Venus absorbs only 25 of incident sunlight, while Earth absorbs 70. Venus is warmer because it has a thick carbon dioxide atmosphere causing a greenhouse effect of several hundred degrees. Earth is Goldilocks choice among the planets, the one that is just right for life to exist. Not too hot. Not too cold. How does the Earth manage to stay in this habitable range? Is there a Gaia phenomenon keeping the climate in bounds? A nice idea, but it doesnt work. Today, greenhouse gas levels are unprecedented compared to the last 450,000 years.

greenhouse effect↗
NASA NTRS2019

Consequences of Tidal Dissipation in a Putative Venusian Ocean

The solar tide in an ancient Venusian ocean is simulated using a dedicated numerical tidal model. Simulations with varying ocean depth and rotational periods ranging from minus 243 to 64 sidereal Earth days are used to calculate the tidal dissipation rates and associated tidal torque. The results show that the tidal dissipation could have varied by more than 5 orders of magnitude, from 0.001 to 780 gigawatts (GW), depending on rotational period and ocean depth. The associated tidal torque is about 2 orders of magnitude below the present day Venusian atmospheric torque, and could change the Venusian daylength by up to 72 days per million years depending on rotation rate. Consequently, an ocean tide on ancient Venus could have had significant effects on the rotational history of the planet. These calculations have implications for the rotational periods of similarly close-in exoplanetary worlds and the location of the inner edge of the liquid water habitable zone.

Dynamical evolution and stability↗
NASA NTRS2020

Forecasting Rates of Volcanic Activity on Terrestrial Exoplanets

Similar to the planets and moons in our solar system, terrestrial exoplanets may be shaped by volcanism and tectonics. The magnitudes and rates of geological activity on terrestrial exoplanets will be intimately linked to their sizes and internal heating rates, and can either facilitate, or preclude, the existence of habitable environments. In order to place bounds on the potential for such activity, we estimate total internal heating rates for 52 exoplanets, with masses and radii up to ~ 8M(sub E) and 2R(sub E), respectively, assuming that internal heating is drawn from both radiogenic and tidal sources. We then compare these internal heating rates to those of the bodies in our solar system in an attempt to constrain the rates of volcanic activity on extrasolar worlds. We find that all of the exoplanets surveyed are likely to exhibit volcanic activity at their surfaces. We also find that at least 25% of the of the planets in our study may be extrasolar ocean worlds, the majority of which may contain internal oceans beneath layers of surface ice. These planets may be similar in structure to the icy moons of the giant planets and may have persistent cryovolcanic activity at their surfaces. Volcanic activity on exoplanets could be detected by next-generation space telescopes in transit spectra. In the case of planets with densities and/or effective temperatures that are consistent with H2O-rich compositions, spectral identification of excess water vapor and other molecules that are explosively vented into space during cryovolcanic eruptions could serve as a way to infer the presence of subsurface oceans, and therefore indirectly assess their habitability. Considering the implications for habitability, our results suggest that characterizing Earth-like exoplanets in terms of the potential for geological activity at their surfaces should be a priority in the coming years.

Lynnae C Quick↗
NASA NTRS2009

Optical Detection of Life on Exoplanets

We describe what is known about the atmospheric properties (Teff, lob g, [FelH]) and fundamental properties (mass, age, and metal content) of nearby stars and how they influence the habitable zones and habitable eras of these stars. We then take an observer's point of view to assess the ability of optical telescopes to detect photosynthetic or methanogenic life on planets orbiting these stars.

Heap, Sara↗
NASA NTRS2011

The Role of Planetary Dust and Regolith Mechanics in Technology Developments at NASA

One of NASA's long term goals continues to be the exploration of other planets and orbital bodies in our solar system. Our sustained presence through the installation of stations or bases on these planetary surfaces will depend on developing properly designed habitation modules, mobility systems and supporting infrastructure. NASA Glenn Research Center is involved in several technology developments in support of this overarching goal. Two key developments are in the area of advanced filtration and excavation systems. The first addresses the issues posed by the accumulation of particulate matter over long duration missions and the intrusion of planetary dust into spacecraft and habitat pressurized cabins. The latter supports the operation and infrastructure of insitu resource utilization (ISRU) processes to derive consumables and construction materials from the planetary regolith. These two developments require a basic understanding of the lunar regolith at the micro (particle) to macro (bulk) level. Investigation of the relevant properties of the lunar regolith and characterization of the standard simulant materials used in. testing were important first steps in these developments. The fundamentals and operational concepts of these technologies as well as descriptions of new NASA facilities, including the Particulate Filtration Testing and the NASA Excavation and Traction Testing facilities, and their capabilities for testing and advancing these technologies will be presented. The test data also serves to validate and anchor computational simulation models.

Agui, Juan H.↗
NASA NTRS2020

Detectability of Molecular Signatures on TRAPPIST-1e through Transmission Spectroscopy Simulated for Future Space-based Observatories

Discoveries of terrestrial, Earth-sized exoplanets that lie within the habitable zone(HZ)of their host stars continu eto occur at increasing rates. Transit spectroscopy can potentially enable the detection of molecular signatures fromsuch worlds, providing an indication of the presence of an atmosphere and its chemical composition, includinggases potentially indicative of a biosphere. Such planets around nearby M-dwarf stars—such as TRAPPIST-1—provide a relatively good signal, high signal-to-noise ratio, and frequent transits for follow-up spectroscopy.However, even with these advantages, transit spectroscopy of terrestrial planets in the HZ of nearby M-stars willstill be a challenge. Herein, we examine the potential for future space observatories to conduct such observations,using a global climate model, a photochemical model, and a radiative transfer suite to simulate modern-Earth-likeatmospheric boundary conditions on TRAPPIST-1e. The detectability of biosignatures on such an atmosphere viatransmission spectroscopy is modeled for various instruments of the James Webb Space Telescope, Large UV/Optical/Infrared Surveyor, Habitable Exoplanet Observatory, and Origins. We show that only CO2at 4.3μm would be detectable at the>5σlevel in transmission spectroscopy, when clouds are included in our simulations.This is because the impact of clouds on scale height strongly limits the detectability of molecules in the atmosphere. Synergies between space- and ground-based spectroscopy may be essential in order to overcome these difficulties.

Daria Pidhorodetska↗
NASA NTRS2020

Possible Climate Histories of Venus Type Worlds

There are two well-known scenarios for Venus’ climate evolution. In one Venus had a long-lived magma ocean phase in its first 100Myr with a steam and CO2 dominated atmosphere. The faint young sun with its high XUV flux would cause photodissociation of the steam atmosphere and hydrodynamic escape would cause most of the hydrogen to escape & left-over oxygen would be absorbed by the magma ocean. Hence Venus would have started out hot and dry and the high D/H ratio measured by Pioneer Venus would be from this period of water loss. The other scenario is that Venus’ magma ocean lifetime would have been roughly the same length of time as Earth’s (~1Myr) and water would have condensed on its surface in its early history and had a short period of habitability before increasing solar insolation through time drove it into a runaway greenhouse. However, results from 2016 showed that if Venus remains in the slowly rotating climate dynamics regime (as seen in exoplanet related climate studies) its cloud albedo feedback would have kept it temperate for possibly billions of years. The only way to confirm which one of these scenarios occurred for Venus is to visit it and make the necessary measurements of noble and volatile gases. But exoplanet observations of young exo-Venus type worlds around young F,G,K dwarf stars may constrain which scenario is more probable for a population of such planets. We present a vision of Venus’ climate history that places it and its exoVenus cousins in an ‘Optimistic Venus Zone’ for ~3 billion years within the conventionally named ‘Venus Zone’ and hence encourage the exoplanet communit as possible habitable environments.

Way, M. J.↗
NASA NTRS2018

Development of Low-Scatter Optical Edges for Starshades

Starshades, combined with future space telescopes, provide the ability to detect Earth-like exoplanets in the habitable zone by producing high contrast ratios at small inner working angles. The primary function of a starshade is to suppress light from a target star such that its orbiting planets are revealed. In order to do so, the optical edges of the starshade must maintain their precise in-plane profile to produce the necessary apodization function. However, an equally important consideration is the interaction of these edges with light emanating from our own Sun as scattered and/or diffracted sunlight can significantly degrade the achievable contrast. This paper describes the technical efforts performed to obtain precision, low-scatter optical edges for future starshades. Trades between edge radius (i.e. sharpness) and surface reflectivity have been made and small-scale coupons have been produced using scalable manufacturing processes. A custom scattered light testbed has been developed to quantify the magnitude of scattered light over all sun angles. Models have also been developed to make predictions on the level of reflected and/or diffracted light for various edge architectures. The results of these studies have established a current baseline approach which implements photochemical etching techniques on thin metal foils.

Bradley, Christine↗