atmosphere Archives - Page 116 of 132 - Astrobiology

An artist’s rendering of the warm exoplanet WASP-80 b whose color may appear bluish to human eyes due to the lack of high-altitude clouds and the presence of atmospheric methane identified by NASA’s James Webb Space Telescope, similar to the planets Uranus and Neptune in our own solar system. Image credit: NASA.

Astrochemistry, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Press Release

Methane And Water Found In The Atmosphere Of Exoplanet WASP-80 b

by Keith CowingNovember 22, 2023November 22, 2023

NASA’s James Webb Space Telescope observed the exoplanet WASP-80 b as it passed in front of and behind its host star, revealing spectra indicative of an atmosphere containing methane gas […]

A summary of planet properties at the onset of XUV photoevaporation from models in Figure 6 with constant equilibrium temperatures of 600K, 900K, 1200K, and 1500K in blue, green, orange and red respectively. We assume the disc disperses at 𝑡disp = 3 × 106 yrs with a disc dispersal timescale of 𝜏disp = 105 yrs, all of which lead to XUV photoevaporation dominating at ∼ 4 Myrs, which coincides with the local protoplanetary disc having completely dispersed in these models. The left-hand panel shows the atmospheric mass fraction. Green lines with squares represent results from Owen & Wu (2016), for which boil-off was performed at 900K with initial atmospheric mass fractions of 0.3 and 0.1 in dot-dashed and dotted lines, respectively (note that initial atmospheric mass fractions in our models are calculated self-consistently through gaseous accretion). The right-hand panel shows planet sizes, including those that have been stripped of their atmosphere (atmospheric mass fraction < 10−4 ) and sit on an Earth-like composition line (grey dashed). This panel can be interpreted as a primordial mass-radius distribution. -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Gaia - Planetary Perspectives, Habitable Zones, Status Report

Under The Light Of A New Star: Evolution Of Planetary Atmospheres Through Protoplanetary Disc Dispersal And Boil-off

by Keith CowingNovember 22, 2023November 22, 2023

The atmospheres of small, close-in exoplanets are vulnerable to rapid mass-loss during protoplanetary disc dispersal via a process referred to as `boil-off’, in which confining pressure from the local gas […]

(a) Surface temperature Ts (filled contours) for surface pressure ps = 5 bar and global mean surface optical depth τ = 5. The topography is plotted in blue dashed lines with a contour interval of 1000 m from 1000 m to 5000 m. The horizontal red dashed lines indicate the zone for tropical averaging (see Section 2.2). (b) Same as (a), but for the case with ps = 0.01 bar and τ = 0.01. The horizontal white dashed lines indicate the tropical averaging zone. (c) Relative surface lapse rate, γ (defined in Eq. 5), as a function of greenhouse effect, τ , and atmospheric thickness, ps. The data is sampled on a log-scale grid with τ = 0.003, 0.01, 0.1, 0.3, 1, 3, 5 and ps = 0.01, 0.1, 1, 5 bar. (d) The dependence of γ on τ when ps = 1 bar. Red solid (def): default simulation, obliquity equals zero, no atmospheric condensation, idealized topography, sensible heat flux enabled. Blue solid (obl20): as def, but with obliquity set to 20◦ . Blue dotted (atmo cond): as def, but with obliquity set to 20◦ , and a CO2-like atmospheric condensation is enabled. Magenta (MOLA): as def, but with Mars Orbiter Laser Altimeter topography. Cyan solid (w/o SH): as def, but with sensible heat flux disabled. Red dotted (2-column model): calculations from the simple two-column model (see Section 3.4). (e) As (d), but with varying ps and fixed τ = 0.1. Cyan dotted (fixed ρ in SH): as def, but the value of air density, ρ, is held fixed at the reference value for a 1-bar atmosphere in Eq. (3). -- astro-ph.EP

Arctic / Antarctic / Alpine, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Habitable Zones, Status Report

Why Are Mountaintops Cold? The Transition Of Surface Lapse Rate on Dry Planets

by Keith CowingNovember 20, 2023November 20, 2023

Understanding surface temperature is important for habitability. Recent work on Mars has found that the dependence of surface temperature on elevation (surface lapse rate) converges to zero in the limit […]

Tropical rainforest on Barro Colorado Island, Panama, near the site of the study. Credit: Marcos Guerra, STRI via NSF

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Gaia - Planetary Perspectives, Habitable Zones, Plant Biology, Press Release

New Research Suggests Plants Might Be Able To Absorb More CO2 From Human Activities Than Previously Expected

by Keith CowingNovember 19, 2023November 19, 2023

New research published today in leading international journal Science Advances paints an uncharacteristically upbeat picture for the planet. This is because more realistic ecological modelling suggests the world’s plants may […]

Outgoing thermal emission as a function of surface temperature. The dashed-dotted line is the classic runaway curve obtained with fully convective profiles, independently from the stellar radiation spectrum and internal flux. With self-consistent profiles, this function depends on the type of the host star and the internal flux ϕint. Dashed curves are obtained with Earth geothermal flux. For T-1 and ϕint < 0.01 Wm−2 , the runaway greenhouse can end without full vaporization of the ocean. Low-pressure liquidus, solidus and melting (melt fraction = 40%) temperatures are indicated for an Earth mantle composition. Surface pressure is 270 bars except in the blue area where Tsurf is below the critical temperature of H2O and psurf is given by the saturation vapor pressure of H2O. These curves are based on the profiles shown in Extended Data Figure 2 -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Lava / magma ocean / Volcanic Worlds, Status Report, Water/Hycean Worlds & Oceanography

A Cool Runaway Greenhouse Without Surface Magma Ocean

by Keith CowingNovember 17, 2023May 11, 2024

Water vapour atmospheres with content equivalent to the Earth’s oceans, resulting from impacts or a high insolation, were found to yield a surface magma ocean. This was, however, a consequence […]

Future radii of planets b, c, d at an age of 5 Gyr. The current radii of planets c, d and b are shown as dashed lines, together with the current and final radii for a range of planetary masses for the outer two planets d and b; the core is represented by a black circle, while the envelope is shown as a colored circle around the core. The core size increases with increasing mass. Note that the size scaling of the envelope compared to the core is arbitrary. It is chosen such that one can easily compare present and final planetary radii and immediately see, which configuration can hold on to some fraction of the envelope and remain above the gap. While the outermost planet b will retain enough envelope to remain well above the radius gap around 1.8 R⊕ for all masses considered, we find that for planet d there is an intermediate mass range between ∼7 to 18 M⊕, for which planets can retain an envelope and survive above the gap. Lower mass planets will experience enough mass loss to completely lose their envelope, while higher mass planets only have very thin envelopes at present age to match the observed radius due to their larger core size, that their thin envelope is easily lost, in spite of their large mass. Planet c is assumed to be rocky at present and will not change its size significantly. The current radius of planet c matches well with the radii predicted for Earth-like rocky cores in the mass regime of 3-5 M⊕. -- astro-ph.HE

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Habitable Zones, Status Report

Three Young Planets Around The K-dwarf K2-198: High-energy Environment, Evaporation History And Expected Future

by Keith CowingNovember 15, 2023November 15, 2023

Planets orbiting young stars are thought to experience atmospheric evaporation as a result of the host stars’ high magnetic activity. We study the evaporation history and expected future of the […]

Responses of the atmospheric pCH4 to biogenic CH4 flux for the case of F-, G-, and Ktype stars (blue, black, and light blue solid lines with dots) (ExpCH4fluxF2V, ExpCH4fluxG2V, and ExpCH4fluxK2V in Table 3). The dotted lines represent the results of the case of the G-type star with the scaled intensity of the spectra at 200–210 nm (0.1, 0.5, 2, 10, and 40 times for purple, light purple, orange, red, and brown lines, respectively). (ExpCH4flux200nm in Table 3). -- astro-ph.EP

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Status Report

Controls of Atmospheric Methane on Early Earth and Inhabited Earth-like Terrestrial Exoplanets

by Keith CowingNovember 14, 2023November 14, 2023

Methane (CH4) is a primarily biogenic greenhouse gas. As such, it represents an essential biosignature to search for life on exoplanets.

Outline of the Ariel Challenge dataset generation. The input parameters are used to generate the synthetic exoplanet spectra and noise arrays. A Nested Sampling is carried by the Ariel Data Challenge Organising team on these synthetic ideal spectra, producing samples of the target parameters. Our Machine Learning model aims to reproduce the samples of parameters of the Nested Sampling. See text for more details. -- astro-ph.EP

AI - Data - Apps - Cybernetics, Ariel Mission, Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Simulation-based Inference for Exoplanet Atmospheric Retrieval: Insights from winning the Ariel Data Challenge 2023 using Normalizing Flows

by Keith CowingNovember 12, 2023October 16, 2024

Advancements in space telescopes have opened new avenues for gathering vast amounts of data on exoplanet atmosphere spectra. However, accurately extracting chemical and physical properties from these spectra poses significant […]

Upper left panel: Comparison of our work to the model results of Mikal-Evans (2022) who assumed a cloud-less Archean-Earth. Grey shading indicated the wavelength range of the figure below. Lower left panel: The transmission spectra of TRAPPIST-1e observed with HST/WFC3 during two different transits (see Zhang et al. 2018). The green lines show our wet alive model results during the Carrington-like event (solid lines - scenario [5], dashed lines - scenario [6]), while the blue lines correspond to the Archean-Earth scenario of Mikal-Evans (2022). Right panel: Comparison of the corresponding assumed atmospheric temperature profiles. -- astro-ph.EP

Exoplanets, -moons, -comets, Imaging & Spectroscopy, Radiation, Space Weather & Heliophysics, Status Report, TRAPPIST-1

Impact of Cosmic Rays on Atmospheric Ion Chemistry and Spectral Transmission Features of TRAPPIST-1e

by Keith CowingNovember 10, 2023November 10, 2023

Ongoing observing projects like the James Webb Space Telescope (JWST) and future missions offer the chance to characterize Earth-like exoplanetary atmospheres. Thereby, M-dwarfs are preferred targets for transit observations, for […]

Best-fit occultation depths of individual CHEOPS visits (blue) along with their posteriors on the right. The horizontal solid and dashed lines represent the mean occultation depth of 82.4 ± 5.6 ppm. The panel on the right-side displays the best-fit posterior distribution. The green shaded regions indicate the span of the TESS Sectors 40, 41 and 54 while the brown points indicate sector-wise occultation depth. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

CHEOPS Observations Of KELT-20 b/MASCARA-2 b: An Aligned Orbit And Signs Of Variability From A Reflective Dayside

by Keith CowingNovember 8, 2023November 8, 2023

Occultations are windows of opportunity to indirectly peek into the dayside atmosphere of exoplanets. High-precision transit events provide information on the spin-orbit alignment of exoplanets around fast-rotating hosts.