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A Geologic Map of the Asteroid Belt

EOS - Mon, 04/28/2025 - 12:59

Where do meteorites come from? A new analysis of 75 fall events suggests that meteorites with different geologies travel from different places in the asteroid belt, which separates Mars and Jupiter. Researchers traced some types of meteorites to particular asteroid families, creating a geologic map of meteorite origins. Most meteorites were generated by just a few recent collisions between asteroids.

“Understanding the asteroid belt is really looking into the past, into the formation of the solar system, and into all the dynamics that happened at that time,” said Peter Jenniskens, coauthor on the new analysis and a meteorite astronomer at the SETI Institute in Mountain View, Calif. Those early interactions and collisions matter because much of the water on Earth and a lot of the organics likely came from primitive asteroids, he added.

Tracking Falls

Spacecraft have returned small volumes of material from the Moon, comets, and asteroids, but meteorites remain the primary way that scientists get their hands on space rocks.

“By reconstructing where specific meteorite types formed, we gain a clearer picture of the compositional and thermal gradients that existed when the solar system was young,” said Michaël Marsset, an astronomer at the European Southern Observatory in Santiago, Chile. “This has major implications for understanding how habitable environments emerge, not just here but potentially in other planetary systems as well.” Marsset studies small solar system objects and Earth impactors and was not involved in the new study.

But matching a meteorite to the asteroid it came from is a tall task.

“Asteroids in space look quite a bit different than the meteorites that we have in our laboratories.”

“Asteroids in space look quite a bit different than the meteorites that we have in our laboratories, because the asteroids in space are covered by regolith and debris and they are exposed to solar radiation and solar wind,” Jenniskens said. A meteorite might come from an asteroid’s interior, which could look entirely different from its surface. That makes it challenging to use astronomical observations alone to match meteorites to their asteroid parents.

When someone witnesses a meteorite falling to Earth, scientists can try to backtrack its orbit to a point of origin. Combining this information with the meteorite’s geochemistry, mineralogical structure, and age, they can then figure out which asteroid or asteroid family—a group of asteroids that originate from the same collision event—sent it hurtling toward Earth.

The trouble is that meteorites fall more or less at random, Jenniskens explained. It has taken a while to document enough falls to spot patterns, he said. Just 6 years ago, there were fewer than 40 meteorite falls with well-measured trajectories.

“The number of falls has doubled since that time,” Jenniskens said.

Meteorite researchers have set up more than 2 dozen global camera networks that have detected many of these recent falls—roughly 14 falls per year. Also, the rising popularity of dash cameras and doorbell cameras has contributed to the surge of recent detections.

In the new analysis, about 36 of the 75 falls were recorded by residential security cameras, Jenniskens said. People report fireball sightings and submit videos for analysis. “We really depend on the citizen science.”

Meteorite Ancestry

Jenniskens and his colleague Hadrien Devillepoix of Curtin University in Perth, Australia, reviewed the trajectories, geochemistry, mineralogy, and size of 75 meteorites. They also looked at the meteorites’ ages, calculated on the basis of how long a rock’s surface has been exposed to cosmic rays.

Though a few asteroids are suspected sources of certain meteorite types, a meteorite’s age was often the key factor in figuring out which asteroid family produced the meteorite. The positions and movements of asteroids within a family evolve in a predictable way over time, and if this so-called dynamical age matched a meteorite’s cosmic ray age, that family was more likely to be the meteorite’s source.

NASA’s Dawn spacecraft orbited asteroid 4 Vesta and mapped its surface geology and chemistry. Debris from impacts that made some of these craters makes it way to Earth as HED meteorites. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA, Public Domain

Most of the meteorites originated from a handful of asteroid families, and different classes of meteorites could be traced to different parts of the asteroid belt.

Jenniskens and Devillepoix confirmed that very low iron LL-type meteorites, such as the Chelyabinsk meteorite, originated from the extensive Flora family in the inner asteroid belt. They tracked H-type chondrites to debris clusters in the Koronis, Massalia, and Nele families. They also traced low-iron L chondrites to the Hertha asteroid family, rather than to the previously determined Massalia family.

“Hertha is covered by dark rocks that were shock blackened, indicative of an unusually violent collision,” Jenniskens said. “The L chondrites experienced a very violent origin 468 million years ago when these meteorites showered Earth in such numbers that they can be found in the geologic record.”

“It turns out that, yes, our HED meteorites seem to come from Vesta, not from its family.”

Marsset has also worked to trace meteorites to their asteroid origins, though his team used astronomical observations of asteroids and numeral modeling, rather than meteorite data. “Even with these different approaches, we’re mostly converging on similar conclusions,” Marsset said. “Where we disagree, well, that’s part of the fun! For example, I’d gladly bet a pint with Dr. Jenniskens and Dr. Devillepoix that L chondrites come from the Massalia family, not Hertha,” he joked.

The team also looked at howardite, eucrite, and diogenite (HED) meteorites, achondrites that have long been tied to the Vesta asteroid family. According to the new analysis, the volume of HED material that made its way to Earth must have come from a collision so large that only something as large as Vesta would have survived. (Vesta is the second-largest object in the asteroid belt.) What’s more, the cosmic ray exposure ages of HED meteorites closely match the ages of particular impact craters on Vesta’s surface that were mapped by NASA’s Dawn spacecraft.

“It turns out that, yes, our HED meteorites seem to come from Vesta, not from its family,” Jenniskens said.

Decoding Solar System History

“What’s remarkable about this work is the broader picture it starts to paint,” Marsset said. “We are finally able to map specific classes of meteorites that fall on Earth to distinct regions in the asteroid belt and to specific asteroid families.… That’s a major step toward understanding the compositional structure of the asteroid belt and, ultimately, how our solar system formed and evolved.”

But it’s just as important to understand where meteorites aren’t coming from, he pointed out.

“While one might expect the meteorite flux to represent a broad sampling of material from across the entire asteroid belt, we now know that it is actually dominated by a few recent fragmentation events,” Marsset said. “This insight helps us better understand the natural sampling bias in the meteorites we collect on Earth, and it also highlights which asteroid populations are underrepresented. That, in turn, can guide the targets of future space missions aimed at filling in those missing pieces.”

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

Citation: Cartier, K. M. S. (2025), A geologic map of the asteroid belt, Eos, 106, https://doi.org/10.1029/2025EO250165. Published on 28 April 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Glaciers Offer Clues into the Path of Fossil Fuel Pollution

EOS - Mon, 04/28/2025 - 12:58
Source: Global Biogeochemical Cycles

Glaciers provide a unique opportunity for researchers to measure levels of atmospheric carbon deposition. Unlike other terrestrial ecosystems, these slow-moving rivers of ice do not have other large reservoirs of soil or vegetation that might obscure how much carbon they receive from the atmosphere.

In most terrestrial ecosystems, dissolved organic matter comes from plants and soil and can contain both organic carbon and black carbon (the sooty black product from wildfires and burning fossil fuels). In glaciers, organic matter is predominately derived from in situ microbial production and atmospheric deposition. Both can contribute to downstream food webs and broader biogeochemical cycling.

Understanding how glaciers get their carbon, including how much comes from atmospheric deposition, can help scientists understand how human activity affects the glacier carbon cycle and ecosystems.

Holt et al. investigated dissolved organic matter in the meltwater from 10 glaciers across Alaska, Switzerland, Kyrgyzstan, and Ecuador. By examining dissolved organic carbon and black carbon isotopes, as well as molecular-level composition, researchers found that anthropogenic pollutants significantly influenced the composition of dissolved organic matter in glaciers and that this influence varied by region.

The researchers collected samples from each glacier outflow stream and determined the age of the dissolved organic carbon in the samples. These ages offered an isotopic signature of their sources. For instance, younger samples might originate from wildfire material and microbial activity on the glacier surface, whereas older material more likely originated from ancient carbon sources, namely, fossil fuels.

Each region displayed different amounts of dissolved organic carbon linked to anthropogenic atmospheric pollution, ranging from 12% to 91%, with a median of 50%. Carbon from fossil fuels was more prevalent in the dissolved organic matter of the Alaskan glacier. In Ecuador, there was a higher relative contribution of carbon from biomass burning, such as wildfires, and in situ microbial activity. The exact source, age, and makeup of dissolved organic carbon and dissolved black carbon varied between different glaciers outflows. But overall, the researchers say, fossil fuels are affecting the carbon content in glacier outflow globally, with implications for the ecosystems that depend on them. (Global Biogeochemical Cycles, https://doi.org/10.1029/2024GB008359, 2025)

—Rebecca Owen (@beccapox.bsky.social), Science Writer

Citation: Owen, R. (2025), Glaciers offer clues into the path of fossil fuel pollution, Eos, 106, https://doi.org/10.1029/2025EO250161. Published on 28 April 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Coastal Models Quantify How Natural Islands Respond to Sea Level Rise

EOS - Mon, 04/28/2025 - 12:00
Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Earth’s Future 

Coral atoll islands are particularly vulnerable to sea level rise and climate change. In rural islands where active coastal sediments processes are occurring, wave-driven sediment deposition can raise islands’ crest on their oceanward side.

Roelvink et al. [2025] show that coastal morphodynamic models are now able to provide quantitative insight into these phenomena. Specifically, they show that in the natural islands of Fiyoaree (Maldives), the sediment accumulation on the island crests can mitigate the projected increase of overwash during extreme wave events by a factor of three. Their modeling framework also confirms the benefits of adaptation measures aiming at protecting corals, particularly in reducing incoming wave energy. As climate is warming due to anthropogenic greenhouse gas emissions, increasing sea surface temperatures are causing widespread bleaching and mortality of corals, raising the urgent question of limits to coral adaptation, even at 2 degrees Celsius of global warming.

Hence, the study opens the way for future research exploring these limits in a quantitative manner, while also reminding us about the urgency of mitigating climate change to avoid irreversible losses and damages.

Citation: Roelvink, F. E., Masselink, G., Stokes, C., & McCall, R. T. (2025). Climate adaptation for a natural atoll island in the Maldives – predicting the long-term morphological response of coral islands to sea level rise and the effect of hazard mitigation strategies. Earth’s Future, 13, e2024EF005576. https://doi.org/10.1029/2024EF005576

—Gonéri Le Cozannet, Associate Editor, Earth’s Future

Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Evaluating the performance of the rainfall forecast model based on GNSS ZTD and ERA5 CAPE for Hong Kong

Publication date: Available online 26 April 2025

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Yang Liu, Qiaoling Zhang, Tenglong Wang, Yibin Yao, Mingxian Hu, Haobo Li, Bao Zhang, Chaoqian Xu, Qingzhi Zhao

Atmospheric electric field variations and its correlation with air quality index as observed from two low-latitude Indian stations

Publication date: Available online 24 April 2025

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Rakhijul Alam Faruque, Sujay Pal, Gahul Amin, Sushanta Kumar Mondal

Research on PWV Fusion Based on ERA5 PWV and FY-4A PWV in Chinese mainland

Publication date: Available online 24 April 2025

Source: Journal of Atmospheric and Solar-Terrestrial Physics

Author(s): Wei Du, Yong Wang, Xiao Liu, Jing Huang, Yanping Liu, Xiangshun Meng

Editorial Board

Publication date: May 2025

Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 270

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A physical parameterization for cloudy-sky downward longwave radiation: Validation for tropical and subtropical regions in Brazil

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Simulation and visualizations of solar car motion along the road

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The Effect of Gravity on Equilibrium Evolution of the Semicircular Magnetic Flux Rope

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Assessing temperature and water vapor in the atmospheric column over South America: a synopsis of identified trends using ERA5 reanalysis

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Source: Journal of Atmospheric and Solar-Terrestrial Physics, Volume 271

Author(s): Alexey Andreyev, Vyacheslav Somsikov, Vitaliy Kapytin, Yekaterina Chsherbulova

Understanding the performance of global precipitation products for hydrological modeling in the data-scarce morphologically complex central Himalayan region

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Author(s): Sneha Sandilya, Sunayana Singh, Sonu Kumar, Jitendra Rajput

Leveraging machine learning for accurate PM<sub>2.5</sub> concentration prediction in selected Nigerian locations

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Impact of atmospheric aerosols on air quality of three most polluted cities of Uttar Pradesh, India

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A novel approach to estimate surface refractivity with simple meteorological data

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