Comet Archives

Extraterrestrial Materials Academy (ETMA)

Artemis & Lunar Exploration, Astrochemistry, Astrogeology, Away Teams & Field Reports, Career Opportunities, Comets and Asteroids, Courses, Mars, Meteorites & Asteroids, Moon, Planetary Protection & Biosafety, Sample Return, Status Report

ETMA: Extraterrestrial Materials Academy

by Keith CowingDecember 4, 2025December 4, 2025

The Extraterrestrial Materials Academy (ETMA) is scheduled for June 8–August 15, 2026, at the Lunar and Planetary Institute (LPI) in Houston, Texas, in partnership with the University of Houston–Clear Lake […]

3I spectrum (dots) and the reflectance spectra of three CR and one R chondrite discussed in the text. -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Comets and Asteroids, Icy Worlds, Interstellar, Status Report

Spectrophotometric Evidence For A Metal-bearing, Carbonaceous, and Pristine Interstellar Comet 3I/ATLAS

by Keith CowingNovember 30, 2025November 30, 2025

3I/ATLAS is only the second confirmed cometary object known to enter the Solar System from interstellar space.

Panel (a)-(c) is the snapshots of the REBOUND simulation. Colors represent the angular momentum value of each comet. Those with blue colors have a possibility of entering the inner solar system. The pentagram symbol denotes the Sun, the gray trajectory represents the flyby path of HD7977, and the purple trace illustrates the orbit of the selected comet. The insets inside each plot show the magnified orbit evolutionary of a selected representative comet. Panel (d) is the distribution of angular momentum change of Inner Oort cloud comets. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Comets and Asteroids, Extinction events, Interstellar, Status Report

On The Coincidence Between The Close Passage Of HD7977 And The Pliocene-Pleistocene Transition

by Keith CowingNovember 24, 2025November 24, 2025

The Oort Cloud’s dynamical evolution is significantly influenced by both the galactic tide and stellar flybys.

Interstellar Comet 3I/ATLAS As Seen By NASA's MAVEN Mission Larger imagery

Astrochemistry, Astrogeology, Astronomy & Telescopes, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Interstellar, Press Release

Interstellar Comet 3I/ATLAS As Seen By MAVEN

by Keith CowingNovember 19, 2025November 19, 2025

An ultraviolet image composite of the hydrogen atoms surrounding comet 3I/ATLAS, the third interstellar object ever detected by astronomers, as it passes through our solar system.

The distribution of planets, main comet and asteroid belts around the Sun, and the equivalent analogues for Beta Pictoris and WD 1145+017. All distances are logarithmic, scaled such that they all have the same equilibrium temperature for a blackbody, meaning that the various sublimation lines are at the same x-axis locations for comparison. Distances from each star are labelled in stellar radii (upper scale) and astronomical units (lower scale). For the Sun, Solar system comets are shown with notable associated distances, belts and planets. For β Pictoris, the planets and main belts are noted. For the white dwarf WD 1145+017 the locations for the six transiting bodies are indicated, with a zoomed-in panel showing their labelled order from Vanderburg et al. (2015). -- astro-ph.EP

Astrochemistry, Astrogeology, Comets and Asteroids, Exoplanets, -moons, -comets, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

An Overview Of Exocomets

by Keith CowingNovember 13, 2025November 13, 2025

We give a general overview of what the scientific community refers to as “exocomets”.

The temperature versus depth and time for 𝜅 = 10−4 W m−1 K−1 , 10−3 W m−1 K−1, and 10−2 W m−1 K−1 (top, middle, and bottom panels). The sublimation temperatures of CO (30 K, dash), CO2 (80 K, dash-dot), and H2O (150 K, dot) are shown as white contours. The depth of heat penetration and volatile activation strongly depends on the thermal conductivity 𝜅. Note that the range of the 𝑦-axis is different for each panel. -- astro-ph.EP

Astrochemistry, Astrogeology, Astropharmacy / Biotechnology, Biochemistry & Organic Chemistry, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Interstellar, Status Report

Potential Thermal Profiles of The Third Interstellar Object 3I/ATLAS

by Keith CowingNovember 3, 2025November 3, 2025

We investigate the thermal evolution of 3I/ATLAS, the third macroscopic interstellar object discovered on 2025 July 1.

Schematic illustration of interstellar comet 3I/ATLAS showing the expected stratigraphy of an irradiated nucleus. Galactic cosmic ray irradiation over several Gyr alters the outer ∼15–20 m, producing a CO2-rich crust through CO-to-CO2 conversion, ongoing CO release from the breakdown of irradiated organics, an organic-rich refractory mantle with a red spectral slope, and compact amorphous ice characterized by low diffusivity and high thermal conductivity. Beneath this layer lies a pristine, unprocessed interior shielded from GCRs, whose composition and structure remain unknown but are expected to differ markedly from the irradiated crust. -- astro-ph.EP

Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Comets and Asteroids, Icy Worlds, Interstellar, Status Report

Interstellar Comet 3I/ATLAS: Evidence for Galactic Cosmic Ray Processing

by Keith CowingNovember 3, 2025November 3, 2025

Spectral observations of 3I/ATLAS (C/2025 N1) with JWST/NIRSpec and SPHEREx reveal an extreme CO2 enrichment (CO2/H2O = 7.6+-0.3) that is 4.5 sigma above solar system comet trends and among the […]

Astrochemistry, Astrogeology, Comets and Asteroids, Icy Worlds, Interstellar, Status Report

Implications For The Formation Of Oort Cloud-like Structures And Interstellar Comets In Dense Environments

by Keith CowingNovember 3, 2025November 3, 2025

Most stars form in dense stellar environments, where frequent close encounters can strongly perturb and reshape the early architecture of planetary systems.

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Comets and Asteroids, Icy Worlds, Status Report

The First Detection of Molecular Activity in the Largest Known Oort Cloud Comet: ALMA Imaging of C/2014 UN271 (Bernardinelli–Bernstein) at 16.6 au from the Sun

by Keith CowingOctober 24, 2025October 22, 2025

We report observations of comet C/2014 UN271 (Bernardinelli–Bernstein) carried out on UT 2024 March 8 and 17 at a heliocentric distance (rH) of 16.6 au using the Atacama Large Millimeter/submillimeter […]