terrestrial exoplanet Archives

Schematic of episodic atmospheric collapse and regeneration through impacts for a tidally locked planet. A) The planet has a volatile rich atmosphere which redistributes heat from the day- to the nightside. B) Atmospheric escape thins the atmosphere, heat redistribution becomes less efficient, nightside temperatures drop. C) Nightside temperatures have reached the volatile condensation temperature, the atmosphere collapses. D) Volatiles outgassed through volcanism or magma ocean pockets accumulate on the nightside as ice. E) An impactor hits the nightside and vaporises ice and rock. Hot vapour, ejecta, and silicate rain further vaporise the nightside ice sheets (see Section 2.2 for details). An atmosphere is regenerated. -- astro-ph.EP

Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Extinction events, Impact events, Status Report

Atmospheric Collapse And re-inflation Through Impacts For Terrestrial Planets Around M Dwarfs

by Keith CowingOctober 31, 2025October 31, 2025

Detection of an atmosphere around a terrestrial exoplanet will be a major milestone in the field, but our observational capacities are biased towards to tidally locked, close-in planets orbiting M-dwarf […]

Range of best-fit phase curve and eclipse models for TRAPPIST-1 b and c. The detrended data are shown with gray dots and binned data with black dots. Red curves show the light curve model for each JWST program that observed TRAPPIST-1 b and c at 15µm using MIRI F1500W; the shading spans the range of models drawn from the posterior distribution of the day flux, night flux and phase offset for planets b and c from Analysis # 1 at 2-σ. The top panel shows the phase curve from GO 3077; the second row displays the five visits from GO 1177 (PI: Greene); and the third row presents the four visits from GO 2304 (PI: Kreidberg), along with a zoom-in on the double occultation observed in GO 3077. The expected transit and eclipse timings for each planet from [19] are shown in vertical dashed and plain lines respectively (purple for b, orange for c, and green for g). -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report, TRAPPIST-1

First JWST Thermal Phase Curves Of Temperate Terrestrial Exoplanets Reveal No Thick Atmosphere Around TRAPPIST-1 b and c

by Keith CowingSeptember 3, 2025September 3, 2025

We report JWST/MIRI 15 μm phase curves of TRAPPIST-1 b and c, revealing thermal emission consistent with their irradiation levels, assuming no efficient heat redistribution.

The phase curve of a planet over one rotation at eight different illumination phases. The images at the right show renderings of the planet’s illuminated surface throughout the observation. Each curve represents a different viewing geometry, the observer-planet-star angle, with the corresponding planetary illumination phase shown by the colored circles in the legend. The top (blue) curve shows a fully illuminated planet, while the lower curves show various partial illumination scenarios down to a completely dark planet (purple). The gray curve represents the classical edge-on viewing case exhibiting the full range of phase variations. -- astro-ph.SR

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

Requirements For Joint Orbital Characterization of Cold Giants and Habitable Worlds with Habitable Worlds Observatory

by Keith CowingJuly 30, 2025July 30, 2025

We determine optimal requirements for the joint detection of habitable-zone planets and cold giant planets with the Habitable Worlds Observatory (HWO).

Impact on a 3 Gyr-old Earth-sized planet with a small core Rc = 0.2R and L = 25 km (a) and 100 km (b). In each panel, the left half displays the melt fraction and the right half the melting mechanism, with the materials shown at their pre-impact positions. Basaltic crust is shown in light gray and dunitic mantle material in medium-shaded gray. The melt generation farther than 5L from the center of the melt region below the impact point (approximated by z = L) is neglected. -- astro-ph.EP

Astrogeology, Biogeochemical Cycles & Geobiology, Caves, Craters, Mountains, Subsurface, Lava Tubes, Exoplanets, -moons, -comets, Gaia - Planetary Perspectives, Impact events, Mapping, Geodesy, Cartography, Bathymetry, Status Report

The Influence Of Interior Structure And Thermal State On Impact Melt Generation Upon Large Impacts Onto Terrestrial Planets

by Keith CowingJune 25, 2025June 25, 2025

We investigate the melt production of planetary impacts as a function of planet size (R/REarth=0.1-1.5), impactor size (L=1-1000 km), and core size ratio (Rcore/R=0.2-0.8) using a combination of parameterized convection […]

Sketch illustrating the dynamical evolution of the solar system planets during and after disk dissipation. The two-sided arrows represent the existence of mean motion resonances. Blue and brown scatters represent terrestrial bodies, including Venus (V), proto-Earth (E), Theia (T), and Mars (M), and gas giants including Jupiter (J) and Saturn (S). In the disk phase (t ≲1 Myr), terrestrial planets form and migrate convergently. Theia and Earth are in j + 1 : j resonance, where j is the resonance number. At t ≳ 1 Myr, i.e., just after disk dispersal, planets are still locked in a resonance chain. At t ∼ 10 Myr, the outward migrating Saturn excites Jupiter, triggering the giant planet instability (GPI), which also destabilizes the resonance chain and triggers the moon-forming giant impact. After t ∼ 100 Myr, the planets stabilize to the current architecture. -- astro-ph.EP

Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Gas Giants, Status Report

A Resonant Beginning For The Solar System Terrestrial Planets

by Keith CowingJune 5, 2025June 5, 2025

In the past two decades, transit surveys have revealed a class of planets with thick atmospheres — sub-Neptunes — that must have completed their accretion in protoplanet disks.

Distribution of simulated EEC yield (solid contours) and underlying planet population (dotted contours) around FGK-type stars within 20 pc. We show the planetary radius over incident flux distribution, where the color shading represents the relative density of planet occurrences in this parameter space. The colored contours enclose 10% to 100% of the total planet counts, with the innermost contour indicating the highest-density regions. Grey dashed lines represent EEC boundaries around a Sun-like star with S/S⊕ ∈ [0.356, 1.107] and R/R⊕ ∈ [0.8 · S 0.25, 1.4] (Kopparapu et al. 2014; Stark et al. 2019; Quanz et al. 2022b). Top and right margin plots show the individual distributions of incident flux and planetary radius of detected and total underlying populations. Underlying synthetic planet populations are based on Kammerer et al. (2022). -- astro-ph.EP

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

Detecting Atmospheric CO2 Trends as Population-Level Signatures for Long-Term Stable Water Oceans and Biotic Activity on Temperate Terrestrial Exoplanets

by Keith CowingJune 1, 2025June 1, 2025

Identifying key observables is essential for enhancing our knowledge of exoplanet habitability and biospheres, as well as improving future mission capabilities.

Plot of the various HZ limits (solid red and blue lines) and the evolution of instellation and effective temperature at the orbiting distance of each of the outer planets from the current age of the Sun until the RGB tip (see Figure 2). The HZ limit colors and line styles are the same as in Figure 1. During the RGB the instellation increases and the effective temperature decreases with respect to time. Therefore, the tracks evolve such that they enter from the right side and exit at the left side of the figure. Pluto’s track ends inside the axis limits, meaning that Pluto barely exceeds the recent Venus IHZ limit during the RGB. -- NASA NTRS

Astronomy & Telescopes, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report

Multiple Habitable Phases On Outer Exosolar Worlds

by Keith CowingMay 29, 2025May 26, 2025

As stars evolve to higher luminosities during first ascension of the giant branch, previously frozen terrestrial worlds may thaw and host liquid water on their surfaces.

Schematic diagram of steps in the theoretical model. Further description of key parameters, sampled ranges, and calculation procedures is found in Methods. -- astro-ph.EP)

Exoplanets, -moons, -comets, Habitable Zones, Status Report, TRAPPIST-1

Statistical Geochemical Constraints On present-day Water Outgassing As A Source Of Secondary Atmospheres On The TRAPPIST-1 Exoplanets

by Keith CowingMay 8, 2025September 18, 2025

The TRAPPIST-1 planetary system is observationally favorable for studying if planets orbiting M stars can retain atmospheres and host habitable conditions. Recent JWST secondary eclipse observations of TRAPPIST-1 c rule […]

Maps of the lightning flash rate in flashes km−2 yr−1 diagnosed by the M09 scheme in high-resolution UM simulations with the surface pressure of 0.25, 0.5, 1, 2, 4, 10 bar. Note the logarithmic scale of the colour bar. -- astro-ph.EP

Astrochemistry, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Exoplanets, -moons, -comets, Habitable Zones, Status Report

Lightning Activity On A Tidally Locked Terrestrial Exoplanet In Storm-resolving Simulations For A Range Of Surface Pressures

by Keith CowingApril 29, 2025April 29, 2025

Cloudy atmospheres produce electric discharges, including lightning. Lightning, in turn, provides sufficient energy to break down air molecules into reactive species and thereby affects the atmospheric composition.

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 […]

terrestrial exoplanet

Atmospheric Collapse And re-inflation Through Impacts For Terrestrial Planets Around M Dwarfs

First JWST Thermal Phase Curves Of Temperate Terrestrial Exoplanets Reveal No Thick Atmosphere Around TRAPPIST-1 b and c

Requirements For Joint Orbital Characterization of Cold Giants and Habitable Worlds with Habitable Worlds Observatory

The Influence Of Interior Structure And Thermal State On Impact Melt Generation Upon Large Impacts Onto Terrestrial Planets

A Resonant Beginning For The Solar System Terrestrial Planets

Detecting Atmospheric CO2 Trends as Population-Level Signatures for Long-Term Stable Water Oceans and Biotic Activity on Temperate Terrestrial Exoplanets

Multiple Habitable Phases On Outer Exosolar Worlds

Statistical Geochemical Constraints On present-day Water Outgassing As A Source Of Secondary Atmospheres On The TRAPPIST-1 Exoplanets

Lightning Activity On A Tidally Locked Terrestrial Exoplanet In Storm-resolving Simulations For A Range Of Surface Pressures

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

How A Deep-sea Protein Adapts To An Extreme Environment

Fingerprints Inside Our Sun Could Reveal If It Once Swallowed A Planet

Climates Of Gl 514 b

Cosmic Radiation at Flight Altitudes Rises When the Sun Is Less Active

The History Of Enzyme Evolution Embedded In Metabolism