planetesimals Archives

Evolutions of fiducial planetesimals with different chondritic compositions. Each plot is the contour of one quantity across time and radial location. Note that the total radius decreases due to sintering. From top row to bottom: EH, OC, CV, and CI bodies. Physical quantities from left to right: (i) temperature, (ii) condensed + gaseous C abundance normalized to the initial reservoir; > 1 relative abundance occurs due to sintering concentrating C, (iii) porosity and (iv) gas pressure; hatched areas are completely sintered with no meaningful gas pressure. -- astro-ph.EP

Astrochemistry, Astrogeology, Meteorites & Asteroids, Status Report

Modeling Carbon Outgassing From Chondritic Planetesimals

by Keith CowingJune 1, 2026June 1, 2026

The thermochemical evolution of planetesimals is an underprobed stage of volatile delivery to terrestrial planets during their formation, and may contribute to the volatile depletion of the Earth relative to […]

Model prediction for the water budget of the 4 terrestrial planets

Astrochemistry, Astrogeology, Biogeochemical Cycles & Geobiology, Habitable Zones, Mars, Mercury, Status Report, Venus

Astrochemical Inheritance of Terrestrial Planets Water from Local Wet Silicates

by Keith CowingMay 1, 2026May 5, 2026

The delivery of water to the inner Solar System rocky planets, including Earth, remains debated, as standard models assume that they formed from dry grains, inside the snowline of the […]

Impact history should play a crucial role in the search for habitable exoplanets like Earth -- SwRI

Astrochemistry, Astrogeology, Exoplanets, -moons, -comets, Impact events, Lava / magma ocean / Volcanic Worlds, Mars, Mercury, Press Release, Venus

Notable Progress In Understanding The Evolution Of The Terrestrial Planets

by Keith CowingJune 18, 2025June 18, 2025

An SwRI-led team compared the early impact history of Venus and Earth, determining that Venus experienced higher-energy impacts that created a superheated core. Models show these conditions could create Venus’ […]

Astrogeology, Exoplanets, -moons, -comets, Status Report

Compositional Outcomes Of Earth Formation From A Narrow Ring

by Keith CowingMarch 27, 2025March 27, 2025

We address Earth formation from an elemental perspective, using a method similar to Rubie et al. (2015) but with updates from Dale et al. (2023) to simulate the chemical evolution […]

The plots show the regions of planetesimal formation along with the corresponding embryo masses for all simulations in the parameter study. The colored lines outline the regions where planetesimals form in case VC and VCG, for both criteria SIa and SIb. -- astro-ph.EP

Astrogeology, Exoplanets, -moons, -comets, Status Report

Planets And Planetesimals At Cosmic Dawn: Vortices As Planetary Nurseries

by Keith CowingMarch 19, 2025March 19, 2025

Low-mass, metal-enriched stars were likely present as early as cosmic dawn. In this work, we investigate whether these stars could have hosted planets in their protoplanetary disks.

Formation and growth of the disk. Gas surface densities (in g cm-2 ) for the inner 200 AU of the disk are shown at 13, 21, 30, 40, 50 and 60 kyr in (a) – (f). -- astro-ph.GA

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Exoplanets, -moons, -comets, Habitable Zones, Interstellar, Status Report

Habitable Worlds Formed at Cosmic Dawn

by Keith CowingFebruary 25, 2025February 25, 2025

Primordial supernovae were the first, great nucleosynthetic engines in the Universe, forging the elements required for the later formation of planets and life.

An iron meteorite from the core of a melted planetesimal (left) and a chondrite meteorite, derived from a ‘primitive’, unmelted planetesimal (right). Credit: Rayssa Martins/Ross Findlay

Astrochemistry, Astrogeology, Biosignatures & Paleobiology, Habitable Zones, Impact events, Meteorites & Asteroids, Origin & Evolution of Life, Press Release

How Did The Building Blocks Of Life Arrive On Earth?

by Keith CowingOctober 14, 2024October 14, 2024

Researchers have used the chemical fingerprints of zinc contained in meteorites to determine the origin of volatile elements on Earth. The results suggest that without ‘unmelted’ asteroids, there may not […]

Snapshots of the evolution of planetesimal implantation from a simulation from set 234 starting with 61k planetesimals as the gas giants grow. Terrestrial material is colour coded green-blue and jovian material as yellow-brown. After 0.3 million years the growing Jupiter is scattering planetesimals away, some of which are circularised by gas drag into the inner solar system. After 1 Myr the inner solar system is mixed, and by 5 Myr some embryos can be seen. -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Exoplanets, -moons, -comets, Gas Giants, Status Report

Terrestrial Planet Formation During Giant Planet Formation And Giant Planet Migration I: The First 5 Million Years

by Keith CowingOctober 1, 2024October 1, 2024

Terrestrial planet formation (TPF) is a difficult problem that has vexed researchers for decades. Numerical models are only partially successful at reproducing the orbital architecture of the inner planets, but […]

Artist impression of solar system formation. Presolar grains are tiny, solid grains of primitive solar system material that originated before the formation of the Sun. They have been found in many places, including interplanetary dust, meteorites, and even samples from the comet Wild-2 that were returned to Earth by NASA's Stardust mission. Image credit: Gemini Observatory/AURA/Lynette Cook via NASA Astrobiology

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

Accretion of the Earliest Inner Solar System Planetesimals Beyond the Water-snowline

by Keith CowingSeptember 4, 2024September 4, 2024

How and where the first generation of inner solar system planetesimals formed remains poorly understood. Potential formation regions are the silicate condensation line and water-snowline of the solar protoplanetary disk.

A schematic chronology of the early asteroid belt based on the evidence discussed in the text. CAI formation defines t = 0 and primary planetesimals are assumed to form quickly. Within a few hundred thousand years most of the mass is in the form of large planetesimals, which become dominated by magma interiors, as shown by the red line labeled magma fraction. The energy source is 26Al, whose level declines with a half-life of 0.717 Ma from an assumed initial value of 4 at t = 0, where a level of 1 corresponds to the amount of energy (1.6 kJ/g) needed to just reach the liquidus of a perfectly insulated cold primitive starting material. Chondrules formed between ∼1-4 Ma when exposed to hot magma released during a collision, as illustrated by the drawing in the right hand panel by David A. Harvey (astroart.com) originally depicting the formation of a ring around the Earth. Chondrule formation ends when the LDPs have cooled sufficiently that magma does not reach their surfaces even during collisions. Jupiter may form at around 3-4 Ma and begin clearing the asteroid belt of many of its larger objects. -- astro-ph.EP

Astrochemistry, Astrogeology, Comets and Asteroids, Meteorites & Asteroids, Status Report

Chondrule Formation During Low-Speed Collisions of Planetesimals: A Hybrid Splash-Flyby Framework

by Keith CowingFebruary 21, 2024February 21, 2024

Chondrules probably formed during a small window of time ∼1-4 Ma after CAIs, when most solid matter in the asteroid belt was already in the form of km-sized planetesimals.