atmosphere Archives - Page 121 of 132 - Astrobiology

Bacterial evolution through geological time. (a) The early evolution of bacterial genetic diversity in the Archaean (David and Alm 2010) is reflected by rapid increase in gene content disparity (see Supplementary Material). (b) A persistent higher diversification rate of aerobes since the GOE. The line charts the relative diversification rate (the ratio of the inverse of the waiting time to the next speciation event) for aerobic and anaerobic lineages, revealing a persistent higher diversification rate of aerobes for most of the Earth’s history since the GOE. Rates equilibrated prior to the NOE, before a return to higher diversification rates for aerobes since the GOE. The dotted line denotes a ratio of 1, where the diversification rate of aerobic and anaerobic lineages is equal. Terminal branches were omitted and ratios since 100 Mya were not calculated do to a low number of nodes. (c) Spread of aerobic metabolism by HGT. Transitions from anaerobic to aerobic lifestyles have outnumbered transitions in the reverse direction/back transitions/returns to anaerobicity for most of Earth history since the GOE. The plots show the ratio of aerobic to anaerobic transition rates on the dated species tree during each time period. The dotted line denotes a ratio of 1, where transitions occur in both directions at the same rate. The small number of nodes since ~200 Ma greatly increases uncertainty for both analyses, as reflected in the wide confidence intervals of posterior node age estimates. Ratios since 100 Mya were not calculated due to a low number of nodes. (d) shows the number of aerobic lineages according to Figure 2, e) qualitative sketch of atmospheric oxygen levels through time based on (Lyons, Reinhard, and Planavsky 2014; Poulton et al. 2021; Krause et al. 2022). The grey line shows the Moon-forming impact at ~4.52 Ga; the green line at ~3.23 Ga reflects the presence of fossil and isotopic evidence for oxygenic photosynthesis; the red line at ~2.33 Ga reflects the end of the GOE (see calibrations in Supplementary Material). --- biorxiv.org

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Microbiology & Virology, Origin & Evolution of Life, Status Report

An Evolutionary Timescale For Bacteria Calibrated Using The Great Oxidation Event

by Keith CowingAugust 16, 2023August 16, 2023

Most of life’s diversity and history is microbial but it has left a meagre fossil record, greatly hindering understanding of evolution in deep time.

Phanerozoic biodiversity curves. (a) Total Phanerozoic diversity based on raw data82 divided into its three main Evolutionary Faunas (EF), i.e. the Cambrian trilobites, the Paleozoic brachiopods, and the modern gastropods. Tese are three distinct types of fauna whose diversity pattern expanded and contracted in a similar fashion throughout the diferent phases of the Phanerozoic. Each EF includes specifc taxonomic classes that were most abundant during (but not limited to) a certain period in Earth’s history. Furthermore, the EFs successively replaced one another as the principal group throughout the Phanerozoic. Te red arrows represent the Big Five mass extinction events, including the Ordovician–Silurian extinction (~445 Ma ago), Devonian extinction (~375 Ma ago), Permian–Triassic extinction (~250 Ma ago), Triassic-Jurassic extinction (~200 Ma ago) and the Cretaceous-tertiary extinction (~66 Ma ago)81. (b) Corrected biodiversity curve using the shareholder quorum subsampling (SQS) sample standardization method34. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Habitable Zones, Status Report

Variations In Climate Habitability Parameters And Their Effect On Earth’s Biosphere During The Phanerozoic Eon

by Keith CowingAugust 16, 2023August 16, 2023

Essential insights on the characterization and quality of a detectable biosphere are gained by analyzing the effects of its environmental parameters. We compiled environmental and biological properties of the Phanerozoic […]

The full posterior distributions (corner plots) of the Proterozoic Earth-like scenario with 1% of Modern Earth’s O2. The different cases explore a combination of different wavelength bands used for the retrieval process. The black lines in the corner plots refer to the true value used to simulate the data. -- astro-ph.EP

Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Habitable Zones, Imaging & Spectroscopy, Status Report

Reflected Spectroscopy Of Small Exoplanets III: Probing The UV Band To Measure Biosignature Gasses

by Keith CowingAugust 16, 2023August 16, 2023

Direct-imaging observations of terrestrial exoplanets will enable their atmospheric characterization and habitability assessment. Considering the Earth, the key atmospheric signatures for the biosphere is O2 and the photochemical product O3.

Brightness temperature spectra for the dayside hemisphere of selected modeled environments for TRAPPIST-1 c with JWST with points corresponding to the model spectra convolved to the F1500W filter band, over the full-wide half-max of the band’s wavelength extent (horizontal error bars). We also show the data point measured by Zieba et al. (2023), along with lines corresponding to blackbody temperatures for day-side with zero heat redistribution (dark grey dashed) and for a blackbody with perfect heat redistribution (light gray dashed). The best fit atmospheres are the 0.1 bar, O2-dominated atmospheres, at 0.5–1.0σ from the measured eclipse depth. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Habitable Zones, Imaging & Spectroscopy, Status Report, TRAPPIST-1

Potential Atmospheric Compositions of TRAPPIST-1 c constrained by JWST/MIRI Observations At 15 μm

by Keith CowingAugust 14, 2023August 14, 2023

The first JWST observations of TRAPPIST-1 c showed a secondary eclipse depth of 421+/-94 ppm at 15 um, which is consistent with a bare rock surface or a thin, O2-dominated, […]

55 Cancri e

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

The Transient Outgassed Atmosphere of 55 Cancri e

by Keith CowingAugust 14, 2023August 14, 2023

The enigmatic nature of 55 Cancri e has defied theoretical explanation. Any explanation needs to account for the observed variability of its secondary eclipse depth, which is at times consistent […]

Some calculated properties from the slowing down of photoelectrons. Top: Fraction of the photoelectron initial energy E0 that is transferred to the gas in elastic collisions. Bottom: Number of secondary ions created by a photoelectron of initial energy E0, normalized by E0. The three color-style combinations refer to pure H (black, long dashed), pure O (black, dotted), and an O-H mixture with fOn/Hn=1/2 (blue, solid). For each mixture, the four curves that are displayed (distinguishable by their thickness) refer to fractional ionizations log10(xe)=−1 (thickest), −2, −3, and −4 (thinnest). Although not shown for the sake of clarity, the Eelas/E0 ratio for E0≳100 eV for pure H becomes essentially independent of fractional ionization at xe

Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report, TRAPPIST-1, Water/Hycean Worlds & Oceanography

Heating And Ionization By Non-thermal Electrons In The Upper Atmospheres Of Water-rich Exoplanets

by Keith CowingAugust 14, 2023August 14, 2023

Context. The long-term evolution of an atmosphere and the remote detectability of its chemical constituents are susceptible to how the atmospheric gas responds to stellar irradiation. The response remains poorly […]

Mass fraction of 4 different PAHs, H2O, CH4, HCN, CO, and C2H2 for transiting planet (Teff = 1300K, Tint = 200K, [Fe/H] = 1.0, and log(g) = 3.0) for different C/O ratios -- astro-ph.EP

Astrochemistry, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Polycyclic Aromatic Hydrocarbons in Exoplanet Atmospheres I. Thermochemical Equilibrium Models

by Keith CowingAugust 14, 2023August 14, 2023

Context: Polycyclic Aromatic Hydrocarbons, largely known as PAHs, are widespread in the universe and have been identified in a vast array of astronomical observations from the interstellar medium to protoplanetary […]

Artist impression of an exoplanet system - ESA

Ariel Mission, Astronomy & Telescopes, Exoplanets, -moons, -comets, Missions & Hardware, Press Release

Exoplanet Surveyor Ariel Passes Major Milestone

by Keith CowingAugust 12, 2023October 16, 2024

Ariel, ESA’s next-generation mission to observe the chemical makeup of distant exoplanets, has passed a major milestone after successfully completing its payload Preliminary Design Review (PDR).

Mantle temperature field and velocity field of superEarth 55 Cancri e for the reference model. High velocities (larger than three times the mean mantle velocity) are plotted with a red arrow. The magma ocean is indicated in red (fully molten) and orange (partially molten). -- astro-ph.EP

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Lava / magma ocean / Volcanic Worlds, Status Report

Interior Dynamics Of Super-Earth 55 Cancri e

by Keith CowingAugust 3, 2023May 11, 2024

The ultra-short-period super-Earth 55 Cancri e has a measured radius of 1.8 Earth radii. Previous thermal phase curve observations suggest a strong temperature contrast between the dayside and nightside of […]

The full modern-Earth high-resolution spectrum from the spectral grid in Susemiehl et al. (accepted), with a zero cloud fraction. We show the full resolution (R) of 500 (shown in pink, top panel), the spectrum binned to R=140 that are used in the nested sampling simulations conducted in this work, (shown in purple, middle panel), and a spectrum at R=70 for reference (shown in dark purple, bottom panel). We also present the bandpass centers used in this study as dots (only in the top panel), and the first and last 20% bandpasses shaded in grey. We note that bandpasses overlap heavily with each other, so we only show the first and last for clarity. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

Bayesian Analysis for Remote Biosignature Identification on exoEarths (BARBIE) I: Using Grid-Based Nested Sampling in Coronagraphy Observation Simulations for H2O

by Keith CowingAugust 3, 2023

Detecting H2O in exoplanet atmospheres is the first step on the path to determining planet habitability. Coronagraphic design currently limits the observing strategy used to detect H2O, requiring the choice […]