Planetesimal Archives

Optical images of the Fomalhaut system in 2012 and 2023. Both panels are white light HST/STIS images.

Exoplanets, -moons, -comets, Fomalhaut, Imaging & Spectroscopy, Status Report

A Second Planetesimal Collision In The Fomalhaut System

by Keith CowingDecember 22, 2025December 22, 2025

The nearby star Fomalhaut is orbited by a compact source, Fomalhaut b, which has previously been interpreted as either a dust-enshrouded exoplanet or a dust cloud generated by the collision […]

This composite Hubble Space Telescope image shows the debris ring and dust clouds cs1 and cs2 around the star Fomalhaut. Fomalhaut itself is masked out to allow the fainter features to be seen. Its location is marked by the white star. Image: NASA, ESA, Paul Kalas (UC Berkeley); Image Processing: Joseph DePasquale (STScI)

Astrogeology, Astronomy & Telescopes, Comets and Asteroids, Exoplanets, -moons, -comets, Fomalhaut, Imaging & Spectroscopy, Press Release, Stellar Cartography

Hubble Sees Asteroids Colliding at Nearby Star for First Time

by Keith CowingDecember 19, 2025December 19, 2025

Like a game of cosmic bumper cars, scientists think the early days of our solar system were a time of violent turmoil, with planetesimals, asteroids, and comets smashing together and […]

Images of the total intensity of scattered light from debris disks detected with IRDIS, IFS, or ZIMPOL. The white bar at the bottom of each image corresponds to 1″. In all images, sky north is up and east is to the left. Original image -- Astronomy and Astrophysics

Astrochemistry, Astrogeology, Astronomy & Telescopes, Comets and Asteroids, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Press Release

SPHERE’s Debris Disk Gallery: Tell-tale Signs Of Dust And Small Bodies In Distant Solar Systems

by Keith CowingDecember 10, 2025December 10, 2025

Observations with the instrument SPHERE at ESO’s Very Large Telescope have produced an unprecedented gallery of “debris disks” in exoplanetary systems. Gaël Chauvin (Max Planck Institute for Astronomy), project scientist […]

Mass fraction (left) and oxygen budget (right) for the detected heavy elements in WD 1647+375. The error bar represents the total uncertainty on the oxygen budget. -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Icy Worlds, Imaging & Spectroscopy, Status Report

Discovery Of An Icy And Nitrogen-rich Extrasolar Planetesimal

by Keith CowingSeptember 22, 2025September 22, 2025

White dwarfs accreting planetary debris provide detailed insight into the bulk composition of rocky exo-planetesimals. However, only one Kuiper-Belt analogue has been identified in that way so far.

Compilation of pebble mass flux vs. time evolutions. Solid lines show models developed in this study for various gap positions (see Sect. 3.1), which can be compared to mass fluxes required in pebble accretion simulations to form diverse inner planetary systems (dashed area, see M. Lambrechts et al. 2019) and the pebble mass flux inferred for the inner solar system using models capable of matching the NC/CC isotopic dichotomy (red dashed, see T. Lichtenberg et al. 2021). Symbols show ages and cold water masses of all 21 objects in our sample computed from JWST/MIRI line ratios (Table 1) in combination with Eq. 4 (see Appendix A), and the left and right y-axes are related through Eq. 3. Symbol color corresponds to inner gap position as obtained from high-spatial-resolution ALMA observations (see Sect. 2) and error-bars reflect uncertainties in measured line ratios. -- astro-ph.EP

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Icy Worlds, Status Report

Cosmic Cascades: How Disk Substructure Regulates The Flow Of Water To Inner Planetary Systems

by Keith CowingAugust 15, 2025August 15, 2025

The influx of icy pebbles to the inner regions of protoplanetary disks constitutes a fundamental ingredient in most planet formation theories.

Final size of protoplanets after 2 My of Hill regime pebble accretion, for different Stokes numbers of silicate and metal pebbles. The plot shows protoplanet mass relative to Earth (white contours and shading) and protoplanet metal mass fraction (black contours) as functions of the Stokes numbers of metal and silicate pebbles. The red dots represent chondrule and metal grain Stokes numbers based on measured size and density in the Kelly (K), Bjurbole (B), and Hammond Down (H) chondrites, respectively. The turquoise box indicates the implied range of pebble Stokes numbers, including individual metal grains and metal grain aggregates. The red contour corresponds to an Earth-like (Fe+Ni)/Si mass ratio of 2.06 and defines our preferred models with protoplanetary masses between 0.35 and 0.7 Earth masses. -- astro-ph.EP

Astrochemistry, Astrogeology, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Status Report

Building Earth With Pebbles Made Of Chondritic Components

by Keith CowingJuly 23, 2025July 23, 2025

Pebble accretion provides new insights into Earth’s building blocks and early protoplanetary disk conditions.

The result of 100 successful simulations of the back20 model (the ring at 0.85 au with a 20% background) that produced a good match to all terrestrial planets (as defined in Section 3.1). The black dots show the results of individual simulations with good final planets. The bigger red dots are the real planets. Note that we do not exclude simulations that produced additional bodies with m < 0.05 MEarth in the Mars region (1.2 < a < 1.8 au). Some of these bodies would collide with Mars at t > 200 Myr (these simulations were terminated at 200 Myr). -- astro-ph.EP

Astrogeology, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Impact events, Status Report

Terrestrial Planet Formation From Two Source Reservoirs

by Keith CowingJuly 22, 2025July 22, 2025

This work describes new dynamical simulations of terrestrial planet formation. The simulations started at the protoplanetary disk stage, when planetesimals formed and accreted into protoplanets, and continued past the late […]

Eccentricity and position snapshots over time of a simulation using the mixed scenario where all 4 terrestrial planets fit constraints and the Earth analogue had a final CC embryo impact. Snapshots are shown over time, including the moment after the final giant impact. The initial NC embryos and planetesimals are shown with the embryos in black and the planetesimals in orange, as well as the CC embryos and planetesimals in blue with Jupiter and Saturn in black on the far right. The final snapshot is the real solar system. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Extinction events, Impact events, Mars, Mercury, Moon, Status Report, Venus

Dynamical Origin Of Theia, The Last Giant Impactor On Earth

by Keith CowingJuly 4, 2025July 4, 2025

Cosmochemical studies have proposed that Earth accreted roughly 5-10% of its mass from carbonaceous (CC) material, with a large fraction delivered late via its final impactor, Theia (the Moon-forming impactor). […]

Evolutionary tracks of the elemental ratios over 3 Myr across all considered scenarios. Ratios are shown in pairs across four key compositional regions: within the H2O snowline (Region 1, top-left), between the H2O and CO2 snowlines (Region 2, topright), between the CO2 and CH4 snowlines (Region 3, bottom-left), and beyond the CH4 snowline (Region 4, bottom-right). Values represent gas-phase elemental ratios, calculated from total elemental abundances averaged over the radial extent of each region and weighted by the surface density of the gas. The colour bars indicate the four chemical scenarios, with time progressing from lighter to darker shades. The three different markers represent the selected grain sizes and are placed along each track every 200 000 yr. The dark marker on each track denotes 1 Myr. Dashed grey lines highlight regions of the parameter space where pairwise comparisons of the elemental ratios provide constraints on specific scenarios or subsets of scenarios. -- astro-ph.EP

Astrochemistry, Astrogeology, Exoplanets, -moons, -comets, Icy Worlds, Status Report, Water/Hycean Worlds & Oceanography

Planet Formation In Chemically Diverse And Evolving Discs — I. Composition Of Planetary Building Blocks

by Keith CowingJune 28, 2025June 28, 2025

Protoplanetary discs are dynamic environments where the interplay between chemical processes and mass transport shapes the composition of gas and dust available for planet formation.

Surface of Ryugu, taken at night by Hyabusa-2's Mobile Asteroid Surface Scout (MASCOT) camera MASCOT/DLR/JAXA

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Ceres, Comets and Asteroids, Imaging & Spectroscopy, Meteorites & Asteroids, Missions & Hardware, Sample Return, Status Report

Challenges and Opportunities in Using Amino Acids to Decode Carbonaceous Chondrite and Asteroid Parent Body Processes

by Keith CowingJune 10, 2025June 10, 2025

Carbonaceous chondrite (CC) meteorites are fragments of planetesimals that hold clues about the early solar system’s organic matter. Amino acids are key to life on Earth; thus their study from […]