Isotopic #evidence for a cold and distant #origin of #3IATLAS {Comet}

 

Abstract

Interstellar objects provide the only directly observable samples of icy planetesimals formed around other stars, and can therefore provide insight into the diversity of physical and chemical conditions occurring during exoplanet formation1−3. Here we report isotopic measurements of the interstellar comet 3I/ATLAS, which reveal an elemental composition unlike any Solar System body. The water in 3I/ATLAS is enriched in deuterium, at a level of D/H = (0.98 ± 0.06)%, which is more than an order of magnitude higher than in known comets, while its range of 12C/13C ratios (141–191 for CO2 and 123–172 for CO) exceeds typical values found in the Solar System, as well as nearby interstellar clouds and protoplanetary disks. Such extreme isotopic signatures indicate formation at temperatures  ≲ 30 K in a relatively metal-poor environment. When interpreted with respect to models for Galactic chemical evolution, the carbon isotopic composition implies that 3I/ATLAS may have accreted as long ago as 12 billion years, following a period of intense, early star formation. 3I/ATLAS thus represents a preserved fragment of an ancient planetary system.

Source: 

Link: https://www.nature.com/articles/s41586-026-10771-6

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#NASA #Update on the #Size Estimate and #Lunar #Impact Probability of #Asteroid 2024 #YR4

Since near-Earth asteroid 2024 YR4 was first discovered in December 2024, NASA and the worldwide planetary defense community have continued to observe the asteroid, which was ruled out as a significant impact risk to Earth. New infrared observations from NASA’s James Webb Space Telescope have decreased the uncertainty of the asteroid’s size and 2024 YR4 is now estimated to be 174-220 feet (53-67 meters), about the size of a 10-story building. The previous size estimate of 131-295 feet (40-90 meters) was derived from visible light measurements from ground-based telescopes.  

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Experts at NASA’s Center for Near Earth Object Studies at the agency’s Jet Propulsion Laboratory have updated 2024 YR4’s chance of impacting the Moon on Dec. 22, 2032 from 1.7% as of late February to 3.8% based on the Webb data and observations from ground-based telescopes. There is still a 96.2% chance that the asteroid will miss the Moon. In the small chance that the asteroid were to impact, it would not alter the Moon’s orbit.  

After mid-April, asteroid 2024 YR4 will be too far and faint to be observed by ground-based telescopes but Webb will observe the asteroid again in May.  

Source: NASA, https://science.nasa.gov/blogs/planetary-defense/2025/04/02/nasa-update-on-the-size-estimate-and-lunar-impact-probability-of-asteroid-2024-yr4/

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