astro-ph.EP] Archives

Water line area maps expressed in units of µmˆ% of continuum. The four observation time windows are July 2011 at 67.09 µm, February 2012 at 66.44 and 67.09 µm, July-August 2012 at 66.44 and 67.09 µm, and January-February 2013 at 66.44 and 67.09 µm. Saturn’s 1-bar level is represented by the black ellipse, with the north pole facing upwards. A selection of iso-latitudes are plotted with grey lines. The rotation axis corresponds to the thin dashed black line. The beam spatial extent is illustrated by the circle in a dashed blue line. The black dots correspond to the central position of the spatial pixels. The position and extension of the beacon (see Table 3) at mid-observation time is represented with the thick dashed black lines. A cubic interpolation was applied to the data. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Enceladus, Icy Worlds, Imaging & Spectroscopy, Saturn, Status Report

Temporal Evolution Of Water Abundance In Saturn’s Hot Vortex Of 2011-2013

by Keith CowingMay 8, 2025May 8, 2025

Water vapour is delivered to Saturn’s stratosphere by Enceladus’ plumes and subsequent diffusion in the planet system. It is expected to condense into a haze in the middle stratosphere.

Biogeochemical Cycles & Geobiology, Biophysics, Biosignatures & Paleobiology, Habitable Zones, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

Comparative Biosignatures

by Keith CowingMay 6, 2025

The discovery of inhabited exoplanets hinges on identifying biosignature gases. JWST is revealing potential biosignatures in exoplanet atmospheres, though their presence is yet to provide strong evidence for life.

Planets emerge from the dense disk of gas and dust encircling young stars. -- NASA

Astrochemistry, Astrogeology, Exoplanets, -moons, -comets, Status Report, Stellar Cartography

Can Close-In Exoplanets Form By Pebble Accretion?

by Keith CowingMay 3, 2025

Pebble accretion is the leading theory for the formation of exoplanets more massive than the Earth.

Uncertain Biosignatures -- Grok/Astrobiology.com

AI - Data - Apps - Cybernetics, Biosignatures & Paleobiology, Exploration Gear & Tech, Genomics, Proteomics, Bioinformatics, Imaging & Spectroscopy, Sample Return, Status Report, Tricorders & Sensors

Life on the Edge: Using Planetary Context to Enhance Biosignatures and Avoid False Positives

by Keith CowingApril 29, 2025

We use a probability theory framework to discuss the search for biosignatures.

CN measurement limits in the exocomet frame for a CN line width of 2.7, 10 and 20 km s−1. Contours show signal-to-noise upper limits. -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Beta Pictoris, Comets and Asteroids, Exoplanets, -moons, -comets, Icy Worlds, Imaging & Spectroscopy, Status Report

Upper Limits On CN From Exocomets Transiting Beta Pictoris

by Keith CowingApril 22, 2025April 22, 2025

The young (23 Myr) nearby (19.4 pc) star β Pictoris hosts an edge-on debris disk with two gas giant exoplanets in orbit around it. Many transient absorption features have been […]

Interpolated stellar luminosity evolution (left) and evolution of the NUV flux in the HZ (right) as a function of host star mass. Scatter points show age and host star mass of the transiting planets in the synthetic planet sample; crosses denote the estimated NUV values in Richey-Yowell et al. (2023). We show three evolutionary tracks for a threshold flux of FNUV,min = 300.0 erg s−1 cm−2 that occupy the HZ (yellow sections) and exceed the threshold NUV flux (red sections) at different times. Where these sections overlap (white rectangles), the requirements for abiogenesis are met and we assign a biosignature detection with probability flife. Planet 1 is an EEC orbiting a K dwarf that never receives sufficient NUV flux for abiogenesis. Planet 2 and Planet 3 enter the HZ at different times and receive sufficient NUV flux for different durations until their respective host star evolves below the threshold. -- astro-ph.EP

Astronomy & Telescopes, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Origin & Evolution of Life, Radiation, Status Report

Bioverse: Potentially Observable Exoplanet Biosignature Patterns Under the UV Threshold Hypothesis for the Origin of Life

by Keith CowingApril 10, 2025April 10, 2025

A wide variety of scenarios for the origin of life have been proposed, with many influencing the prevalence and distribution of biosignatures across exoplanet populations. This relationship suggests these scenarios […]

The sample of known transiting terrestrial planets that orbit mid-to-late M dwarfs within 50pc. Our estimates are noted by solid circles, including PMS and flare corrections. For comparison, the predictions from the Zahnle & Catling (2017) scaling law are shown as open circles. We find that our revised estimates result in historic XUV fluences that are 2.1 times the scaling relation on average, or 3.1 times after considering the PMS and flare corrections. The dashed line indicates the cosmic shoreline as defined in Zahnle & Catling (2017): IXUV ∝ v4esc, with the constant of proportionality defined such that Mars sits on the shoreline. For IXUV in Earth units and vesc in kms−1 , this equation can be written as IXUV = 6.9 × 10−4 v4 esc. The underlying heatmap is colored by our Atmosphere Retention Metric (ARM), indicating the log-space distance from the cosmic shoreline. For legibility, only stars within 15pc are labeled by name; however, all values are given in Table 2. Stars that are still rapidly rotating at the present day are noted with an asterisk; our estimates may be inaccurate in these cases, as the correct answer will be dependent on the age of the star and reliable age estimates for M dwarfs are generally unavailable. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Status Report, Stellar Cartography

The Receding Cosmic Shoreline of Mid-to-Late M Dwarfs: Measurements of Active Lifetimes Worsen Challenges for Atmosphere Retention by Rocky Exoplanets

by Keith CowingApril 3, 2025April 3, 2025

Detecting and characterizing the atmospheres of terrestrial exoplanets is a key goal of exoplanetary astronomy, one that may now be within reach given the upcoming campaign to conduct a large-scale […]

Example of alt-azimuth grid overlay on the Heredia dashboard camera video. Perspective lines on the road define the position of the horizon, and the orientation of a lamp post in different video frames (white lines left, slightly bend halfway up) and features on buildings (right) defines the rotation to normal. The flare elevation (assuming an altitude of 25.1 km) defines the scale. In this case, the camera's central azimuth changed over time and the meteor path in the central frame shown was adjusted using the meteor wake as guidance. -- astro-ph.EP

Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Imaging & Spectroscopy, Impact events, Meteorites & Asteroids, Panspermia, Planetary Protection & Biosafety, Status Report

Orbit, Meteoroid Size, And Cosmic Ray Exposure History Of The Aguas Zarcas CM2 Breccia

by Keith CowingApril 2, 2025April 2, 2025

The Aguas Zarcas (Costa Rica) CM2 carbonaceous chondrite fell during night time in April 2019. Security and dashboard camera video of the meteor were analyzed to provide a trajectory, lightcurve, […]

SED of 51 Eri b and best-fitting Exo-REM models. The top panel illustrates the transmission functions for each photometric filter. The middle panel shows the GPI (black circles, Macintosh et al. 2015; Rajan et al. 2017) and SPHERE (black squares, Samland et al. 2017; Brown-Sevilla et al. 2023) low-resolution spectra of the planet, as well as ground-based L’ and M band photometry (blue squares, Rajan et al. 2017), and the measurements from this work (gold hexagon, for our F410M detection, and gold downward facing triangles for our F335M, F430M, and F460M nondetections). Over plotted is the best-fitting Exo-REM model in magenta, and then 1, 2 σ envelopes showing the range of accepted models. The bottom panel illustrates the residuals to the best-fitting model; there are noticeable residuals in the J band GPI spectrum and the H band SPHERE spectrum that could be related to speckle noise or instrument throughput. The fit shows good agreement to the L’ band and F410M photometry, which constrain the CH4 and CO2 absorption slopes. The M band photometry from Rajan et al. (2017) lies slightly above the best-fitting model, but in general is consistent with strong CO absorption due to vertical mixing. -- astro-ph.EP

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

JWST-TST High Contrast: Living on the Wedge, or, NIRCam Bar Coronagraphy Reveals CO2 in the HR 8799 and 51 Eri Exoplanets’ Atmospheres

by Keith CowingMarch 19, 2025March 19, 2025

High-contrast observations with JWST can reveal key composition and vertical mixing dependent absorption features in the spectra of directly imaged planets across the 3-5 μm wavelength range.

Visualisation of the hypothesis for the observed stripe features, with a reflection grating located at the E ring. A zoomed-in view is shown in the bottom right corner. -- astro-ph.EP

Astrochemistry, Astrogeology, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Comets and Asteroids, Enceladus, Icy Worlds, Imaging & Spectroscopy, Missions & Hardware, Saturn, Status Report

Peculiar Rainbows in Saturn’s E Ring: Uncovering Luminious Bands Near Enceladus

by Keith CowingMarch 9, 2025June 9, 2025

We report observations of stripe-like features in Enceladus’ plumes captured simultaneously by Cassini’s VIMS-IR and ISS NAC instruments during flyby E17, with similar patterns seen in VIMS-IR data from flyby […]

astro-ph.EP]

Temporal Evolution Of Water Abundance In Saturn’s Hot Vortex Of 2011-2013

Comparative Biosignatures

Can Close-In Exoplanets Form By Pebble Accretion?

Life on the Edge: Using Planetary Context to Enhance Biosignatures and Avoid False Positives

Upper Limits On CN From Exocomets Transiting Beta Pictoris

Bioverse: Potentially Observable Exoplanet Biosignature Patterns Under the UV Threshold Hypothesis for the Origin of Life

The Receding Cosmic Shoreline of Mid-to-Late M Dwarfs: Measurements of Active Lifetimes Worsen Challenges for Atmosphere Retention by Rocky Exoplanets

Orbit, Meteoroid Size, And Cosmic Ray Exposure History Of The Aguas Zarcas CM2 Breccia

JWST-TST High Contrast: Living on the Wedge, or, NIRCam Bar Coronagraphy Reveals CO2 in the HR 8799 and 51 Eri Exoplanets’ Atmospheres

Peculiar Rainbows in Saturn’s E Ring: Uncovering Luminious Bands Near Enceladus

Early-career Graduate Students Host An Exclusive, NASA-funded Astrobiology Conference

Intimate Link Between Prebiotic Chemistry And Meteorites: Mechanisms Of Organic Molecule Formation

Microbial Mats Influence The Isotopic Composition And Provenance of Soil Organic Matter In The McMurdo Dry Valleys, Antarctica

Beyond The Prebiotic Soup: Solid Organic Films And Protocell-Like Formation in Prebiotic Discharge Experiments

From Searching For Extraterrestrial Biosignatures To Exploring The Origins Of Life: A Prebiotic Chemistry Perspective