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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 307 records · Page 17
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NASA NTRSDate not supplied

Common Habitat Base Camp for Moon and Mars Surface Operations

The Common Habitat uses the SLS Core Stage Liquid Oxygen tank as the primary structure (similar to Skylab) and has an internal architecture compatible with microgravity, lunar gravity, and Mars gravity, such that identical versions of the same design can be used in all three environments. Applying the large dimensions and eight-person crew size of the Common Habitat to a surface architecture leads to a unique base camp configuration. A notional such base camp is described in this analysis. The base camp includes four distributed zones – habitation, landing, power, and resource production. The base camp is deployed and assembled in three phases: site preparation, element staging, and habitat delivery, each of which are briefly discussed. Crew arrival and departure is discussed, including variations caused by orbital mechanics-induced differences between the Moon and Mars base camps. Trash and logistics operations are described. Finally, crew operations within the base camp are described.

Lunar Outpost↗
NASA NTRS2021

The Far Ultraviolet M-dwarf Evolution Survey. I. The Rotational Evolution of High-energy Emissions

M-dwarf stars are prime targets for exoplanet searches because of their close proximity and favorable properties for both planet detection and characterization. However, the potential habitability and atmospheric characterization of these exoplanetary systems depends critically on the history of high-energy stellar radiation from X-rays to NUV, which drive atmospheric mass loss and photochemistry in the planetary atmospheres. With the Far Ultraviolet M-dwarf Evolution Survey, we have assessed the evolution of the FUV radiation, specifically eight prominent emission lines, including Lyα, of M-dwarf stars with stellar rotation period and age. We demonstrate tight power-law correlations between the spectroscopic FUV features, and measure the intrinsic scatter of the quiescent FUV emissions. The luminosity evolution with rotation of these spectroscopic features is well-described by a broken power law, saturated for fast rotators, and decays with increasing Rossby number, with a typical power-law slope of −2, although likely shallower for Lyα. Our regression fits enable FUV emission-line luminosity estimates relative to bolometric from known rotation periods to within ∼0.3 dex, across eight distinct UV emission lines, with possible trends in the fit parameters as a function of source layer in the stellar atmosphere. Our detailed analysis of the UV luminosity evolution with age further shows that habitable-zone planets orbiting lower-mass stars experience much greater high-energy radiative exposure relative the same planets orbiting more massive hosts. Around early- to mid-M dwarfs, these exoplanets, at field ages, accumulate up to 10–20× more EUV energy, relative to modern Earth. Moreover, the bulk of this UV exposure likely takes place within the first Gyr of the stellar lifetime.

J Sebastian Pineda↗
NASA NTRS2016

Making high accuracy null depth measurements for the LBTI Exozodi survey

The characterization of exozodiacal light emission is both important for the understanding of planetary systems evolution and for the preparation of future space missions aiming to characterize low mass planets in the habitable zone of nearby main sequence stars. The Large Binocular Telescope Interferometer (LBTI) exozodi survey aims at providing a ten-fold improvement over current state of the art, measuring dust emission levels down to a typical accuracy of ~12 zodis per star, for a representative ensemble of ~30+ high priority targets. Such measurements promise to yield a final accuracy of about 2 zodis on the median exozodi level of the targets sample. Reaching a 1σ measurement uncertainty of 12 zodis per star corresponds to measuring interferometric cancellation (“null”) levels, i.e visibilities at the few 100 ppm uncertainty level. We discuss here the challenges posed by making such high accuracy mid-infrared visibility measurements from the ground and present the methodology we developed for achieving current best levels of 500 ppm or so. We also discuss current limitations and plans for enhanced exozodi observations over the next few years at LBTI.

Mennesson, Bertrand↗
NASA NTRS2020

Characterization of stellar activity using transits and its impact on habitability

Stellar magnetic field is the driver of activity in stars and can trigger spots, energetic flares, coronal plasma ejections and ionized winds. These phenomena play a crucial role in understanding the internal mechanisms of the star, but can also have potential effects in orbiting planets. During the transit of a planet, spots can be occulted producing features imprinted in the transit light curve. Here, we modelled these features to characterize the physical properties of the spots (radius, intensity, and location). In addition, we monitor spots signatures on multiple transits to estimate magnetic cycles length of Kepler stars. Flares have also been observed during transits in active stars. We derive the properties of the flares and analyse their UV impact on possible living organisms in planets orbiting in the habitable zone.

Estrela, Raissa↗
NASA NTRS2019

Standard Evaluation of exoplanet Yield for the LUVOIR and HabEx Concept Studies

The HabEx and LUVOIR mission concepts aim to directly image and spectrally characterize potentially habitable exoplanets. We use EXOSIMS to simulate design reference missions with observation scheduling to determine yield of exoplanets detected, spectrally characterized, and orbits determined. EXOSIMS performs dynamically responsive scheduling with realistic mission observing constraints on Monte Carlo universes of synthetic planets around known nearby stars. We use identical astrophysical inputs and the individual observing scenarios of each concept to evaluate a common comparison of the detection and spectral characterization yields of HabEx and LUVOIR. HabEx is evaluated for the 4m hybrid starshade and coronagraph architecture, the 4m coronagraph only architecture, and the 4 m starshade only architecture. LUVOIR is evaluated for the 8 m architecture of their final report. Yield analysis shows that both concepts can directly image and spectrally characterize earth-like planets in the habitable zone and that each concept has complementary strengths.

Keithly, Dean↗
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 NTRS2016

Convection in Condensible-Rich Atmospheres

Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case—water vapor in Earth’s present climate—the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO2 is the condensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamental ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-convective simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere for both steady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.

Convection↗
NASA NTRS2015

Stratospheric Temperatures and Water Loss From Moist Greenhouse Atmospheres of Earth-Like Planets

A radiative-convective climate model is used to calculate stratospheric temperatures and water vapor concentrations for ozone-free atmospheres warmer than that of modern Earth. Cold, dry stratospheres are predicted at low surface temperatures, in agreement with recent 3D calculations. However, at surface temperatures above 350 K, the stratosphere warms and water vapor becomes a major upper atmospheric constituent, allowing water to be lost by photodissociation and hydrogen escape. Hence, a moist greenhouse explanation for loss of water from Venus, or some exoplanet receiving a comparable amount of stellar radiation, remains a viable hypothesis. Temperatures in the upper parts of such atmospheres are well below those estimated for a gray atmosphere, and this factor should be taken into account when performing inverse climate calculations to determine habitable zone boundaries using 1D models.

Astrobiology↗
NASA NTRS2022

TOI-3757 b: A Low-density Gas Giant Orbiting a Solar-metallicity M Dwarf

We present the discovery of a new Jovian-sized planet, TOI-3757 b, the lowest-density transiting planet known to orbit an M dwarf (M0V). This planet was discovered around a solar-metallicity M dwarf, using Transiting Exoplanet Survey Satellite photometry and confirmed with precise radial velocities from the Habitable-zone Planet Finder (HPF) and NEID. With a planetary radius of 12.0 (+0.4 -0.5) R ⊕ and mass of 85.3 (+8.8 -8.7)M ⊕ , not only does this object add to the small sample of gas giants (∼10) around M dwarfs, but also its low density (ρ=0.27 +0.05 -0.04 g) provides an opportunity to test theories of planet formation. We present two hypotheses to explain its low density; first, we posit that the low metallicity of its stellar host (∼0.3 dex lower than the median metallicity of M dwarfs hosting gas giants) could have played a role in the delayed formation of a solid core massive enough to initiate runaway accretion. Second, using the eccentricity estimate of 0.14 ± 0.06, we determine it is also plausible for tidal heating to at least partially be responsible for inflating the radius of TOI-3757b b. The low density and large scale height of TOI-3757 b makes it an excellent target for transmission spectroscopy studies of atmospheric escape and composition (transmission spectroscopy measurement of ∼ 190). We use HPF to perform transmission spectroscopy of TOI-3757 b using the helium 10830 Å line. Doing this, we place an upper limit of 6.9% (with 90% confidence) on the maximum depth of the absorption from the metastable transition of He at ∼10830 Å, which can help constraint the atmospheric mass-loss rate in this energy-limited regime.

Exoplanet astronomy↗
NASA NTRS2021

Starshade Rendezvous: Exoplanet Sensitivity and Observing Strategy

Launching a starshade to rendezvous with the Nancy Grace Roman Space Telescope (Roman) would provide the first opportunity to directly image the habitable zones (HZs) of nearby sunlike stars in the coming decade. A report on the science and feasibility of such a mission was recently submitted to NASA as a probe study concept. The driving objective of the concept is to determine whether Earth-like exoplanets exist in the HZs of the nearest sunlike stars and have biosignature gases in their atmospheres. With the sensitivity provided by this telescope, it is possible to measure the brightness of zodiacal dust disks around the nearest sunlike stars and establish how their population compares with our own. In addition, known gas-giant exoplanets can be targeted to measure their atmospheric metallicity and thereby determine if the correlation with planet mass follows the trend observed in the Solar System and hinted at by exoplanet transit spectroscopy data. We provide the details of the calculations used to estimate the sensitivity of Roman with a starshade and describe the publicly available Python-based source code used to make these calculations. Given the fixed capability of Roman and the constrained observing windows inherent for the starshade, we calculate the sensitivity of the combined observatory to detect these three types of targets, and we present an overall observing strategy that enables us to achieve these objectives.

Andrew Frederic Romero-wolf↗
NASA NTRS2022

Modeling and Performance Analysis of the LUVOIR Coronagraph Instrument

Future space missions such as the Large UV/Optical/Infrared Surveyor (LUVOIR) and the Habitable Exoplanet Observatory, when equipped with coronagraphs with active wavefront control to suppress starlight, will allow the discovery and characterization of habitable exoplanets. The Extreme Coronagraph for Living Planetary Systems (ECLIPS) is the coronagraph instrument on the LUVOIR Surveyor mission concept, an 8- to 15-m segmented telescope. ECLIPS is split into three channels, namely, UV (200 to 400 nm), optical (400 to 850 nm), and near IR (850 nm to 2 μm), with each channel equipped with two deformable mirrors for wavefront control, a suite of coronagraph masks, a low-order/out-of-band wavefront sensor, and separate science imagers and spectrographs. The apodized pupil Lyot coronagraph and the vector vortex coronagraph are the baselined mask technologies for ECLIPS to enable the required 10−10 contrast for observations in the habitable zones of nearby stars for LUVOIR-A (15-m telescope) and LUVOIR-B (8-m telescope), respectively. Their performance depends on active wavefront sensing and control, as well as metrology subsystems to compensate for aberrations induced by segment errors (e.g., piston and tip/tilt), secondary mirror misalignment, and global low-order wavefront errors. Here, we present the latest results of the simulation of these effects for the LUVOIR coronagraph instrument and discuss the achieved contrast for exoplanet detection and characterization after closed-loop wavefront estimation and control algorithms have been applied. Finally, we show simulated observations using high-fidelity spatial and spectral input models of complete planetary systems generated with the Haystacks code framework.

Roser Juanola-Parramon↗
NASA NTRS2022

Simulating Reflected Light Coronagraphy of Earth-like Exoplanets with a Large IR/O/UV Space Telescope: Impact and Calibration of Smooth Exozodiacal Dust

Observing Earth-like exoplanets orbiting within the habitable zone of Sun-like stars and studying their atmospheres in reflected starlight requires contrasts of ∼1e–10 in the visible. At such high contrast, starlight reflected by exozodiacal dust is expected to be a significant source of contamination. Here, we present high-fidelity simulations of coronagraphic observations of a synthetic solar system located at a distance of 10 pc and observed with a 12 m and an 8 m circumscribed aperture diameter space telescope operating at 500 nm wavelength. We explore different techniques to subtract the exozodi and stellar speckles from the simulated images in the face-on, the 30 deg inclined, and the 60 deg inclined case and quantify the remaining systematic noise as a function of the exozodiacal dust level of the system. We find that in the face-on case, the exozodi can be subtracted down to the photon noise limit for exozodi levels up to ∼1000 zodi using a simple toy model for the exozodiacal disk, whereas in the 60 deg inclined case this only works up to ∼50 zodi. We also investigate the impact of larger wave front errors and larger system distance, finding that while the former has no significant impact, the latter has a strong (negative) impact. Ultimately, we derive a penalty factor as a function of the exozodi level and system inclination that should be considered in exoplanet yield studies as a realistic estimate for the excess systematic noise from the exozodi.

Exoplanet detection methods↗
NASA NTRS2021

Planet Matching and Orbit Determination in multi-planet systems for Exoplanet Direct Imaging

A key aspect of the search for Earth-like exoplanets with direct imaging is determining if the exoplanet is in the habitable zone. Future direct imaging mission concepts such as HabEx and LUVOIR require an efficient cadence of observations. Previous work shows that a minimum of three epochs, spanning more than half a period, can determine orbital parameters to 10\% for a single, circular orbit. Multi-planet systems may require a different number and cadence of observations. We begin to address the multi-planet minimum observation approach by considering only the astrometric data of exoplanet candidate objects in high contrast images. Existing multi-planet trajectory matching libraries such as “Orbits For The Impatient” (OFTI) currently require users to specify which point sources belong to which planet and assumes that the user has already matched true-positive detections to planets. Additionally, planet matching needs to be considered when assessing the impact of observation scheduling on trajectory estimation accuracy. To address this need for fitting orbits to multiple objects with limited knowledge, we present an approach using a Monte Carlo study of different observation schedules and planetary systems in which we have developed an algorithm to automatically match observations to planets, and then check the accuracy of the matches. With a large number of cases, we can constrain the number of observations and the spacing necessary to “deconfuse” the detections. We present preliminary planet matching success rates for different observing schedules and planetary system parameters. We use these results to assess the scope of the confusion problem and discuss potential mitigation strategies.

Cahoy, Kerri↗
NASA NTRSDate not supplied

Exo-Venus, Exo-Earth, Exo-Dead in the Trappist 1 System

Since the discovery of the Trappist-1 system a number of studies have explored which of these planets are within the canonical habitable zone with Trappist-1e the most likely Exo-Earth-like of the bunch [e.g. 1,2,3,4]. At the same time they also tend to indicate that Trappist-1d is likely an exo-Venus. Using the ROCKE-3D General Circulation Model we investigate whether Trappist-1d is likely to be an Exo-Venus, an Exo-Earth, or is a bare rock (Exo-Dead). We apply our previous approach to understand the climate history of Venus to explore Trappist-1d.

Trappist-1 system↗
NASA NTRS2022

The Warm Neptune GJ 3470b Has a Polar Orbit

The warm Neptune GJ 3470b transits a nearby (d = 29 pc) bright slowly rotating M1.5-dwarf star. Using spectroscopic observations during two transits with the newly commissioned NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak Observatory, we model the classical Rossiter–McLaughlin effect, yielding a sky-projected obliquity of λ=98 +15 −12 ˚and a v sin i = 0.85 +0.27 −0.33 kms -1 . Leveraging information about the rotation period and size of the host star, our analysis yields a true obliquity of ψ=95 +9 −8 ◦ , revealing that GJ 3470b is on a polar orbit. Using radial velocities from HIRES, HARPS, and the Habitable-zone Planet Finder, we show that the data are compatible with a long-term radial velocity (RV) slope of 𝛾̀=-0.0022±0.0011 ms -1 day -1 over a baseline of 12.9 yr. If the RV slope is due to acceleration from another companion in the system, we show that such a companion is capable of explaining the polar and mildly eccentric orbit of GJ 3470b using two different secular excitation models. The existence of an outer companion can be further constrained with additional RV observations, Gaia astrometry, and future high-contrast imaging observations. Lastly, we show that tidal heating from GJ 3470b’s mild eccentricity has most likely inflated the radius of GJ 3470b by a factor of ∼1.5–1.7, which could help account for its evaporating atmosphere.

Exoplanet astronomy↗
NASA NTRS2023

TOI-5344 b: A Saturn-like Planet Orbiting a Super-solar Metallicity M0 Dwarf

We confirm the planetary nature of TOI-5344 b as a transiting giant exoplanet around an M0-dwarf star. TOI-5344 b was discovered with the Transiting Exoplanet Survey Satellite photometry and confirmed with ground-based photometry (the Red Buttes Observatory 0.6 m telescope), radial velocity (the Habitable-zone Planet Finder), and speckle imaging (the NN-Explore Exoplanet Stellar Speckle Imager). TOI-5344 b is a Saturn-like giant planet (ρ = 0.80 +0.17 −0.15 g cm −3 ) with a planetary radius of 9.7 ± 0.5 R⊕ (0.87 ± 0.04 R Jup ) and a planetary mass of 135 +17 −18 M⊕ (0.42 +0.05 −0.06 M Jup ). It has an orbital period of 3.792622 +0.000010 −0.000010 days and an orbital eccentricity of 0.06 +0.07 −0.04 . We measure a high metallicity for TOI-5344 of [Fe/H] = 0.48 ± 0.12, where the high metallicity is consistent with expectations from formation through core accretion. We compare the metallicity of the M-dwarf hosts of giant exoplanets to that of M-dwarf hosts of nongiants (≲8 R⊕). While the two populations appear to show different metallicity distributions, quantitative tests are prohibited by various sample caveats.

Te Han↗
NASA NTRS2023

A JWST Transmission Spectrum of A Nearby Earth-Sized Exoplanet

The critical first step in the search for life on exoplanets over the next decade is to determine whether rocky planets transiting small M-dwarf stars possess atmospheres and, if so, what processes sculpt them over time. Because of its broad wavelength coverage and improved resolution compared with previous instruments, spectroscopy with the James Webb Space Telescope (JWST) offers a new capability to detect and characterize the atmospheres of Earth-sized, M-dwarf planets. Here we use the JWST to independently validate the discovery of LHS 475 b, a warm (586 K), 0.99 Earth-radius exoplanet, interior to the habitable zone, and report a precise 2.9–5.3 μm transmission spectrum using the Near Infrared Spectrograph G395H instrument. With two transit observations, we rule out primordial hydrogen-dominated and cloudless pure methane atmospheres. Thus far, the featureless transmission spectrum remains consistent with a planet that has a high-altitude cloud deck (similar to Venus), a tenuous atmosphere (similar to Mars) or no appreciable atmosphere at all (akin to Mercury). There are no signs of stellar contamination due to spots or faculae. Our observations show that the JWST has the requisite sensitivity to constrain the secondary atmospheres of terrestrial exoplanets with absorption features <50 ppm, and that our current atmospheric constraints speak to the nature of the planet itself, rather than instrumental limits.

JWST↗
NASA NTRS2024

The Mega-MUSCLES Treasury Survey: X-Ray to Infrared Spectral Energy Distributions of a Representative Sample of M Dwarfs

We present 5–1 × 107 Å spectral energy distributions (SEDs) for 12 M dwarf stars covering spectral types M0–M8. Our SEDs are provided for community use as a sequel to the Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems (MUSCLES) survey. The 12 stars include eight known exoplanet hosts and four stars chosen to fill out key parameter space in spectral type and rotation period. The SEDs are constructed from Hubble Space Telescope ultraviolet spectroscopy and XMM Newton, Chandra, and/or Swift X-ray observations, and completed with various model data, including Lyα reconstructions, PHOENIX optical models, APEC coronal models, and differential emission measure models in the currently-unobservable extreme ultraviolet. We provide a complete overview of the Mega-MUSCLES program, including a description of the observations, models, and SED construction. The SEDs are available as MAST high-level science products and we describe the various data products here. We also present ensemble measurements from our sample that are of particular relevance to exoplanet science, including the high-energy fluxes in the habitable zone and the farultraviolet to near-ultraviolet ratio. Combined with MUSCLES, Mega-MUSCLES provides SEDs covering a wide range of M dwarf spectral types and ages such that suitable proxies for any M dwarf planet host of interest may be found in our sample. However, we find that ultraviolet and X-ray fluxes can vary even between stars with similar parameters, such that observations of each exoplanet host star will remain the gold standard for interpreting exoplanet atmosphere observations.

David J. Wilson↗