SPACE/COSMOS
Taxonomic classification of 80 near-Earth asteroids reveals key insights into their origins, evolution and planetary defense significance
Beijing Zhongke Journal Publising Co. Ltd.
image:
January 27, 2026: Distribution of Near-Earth Asteroids of different taxonomic complexes in the Solar System, where red represents S-complex Near-Earth Asteroids, green represents C-complex ones, and blue represents X-complex ones.
view moreCredit: Beijing Zhongke Journal Publising Co. Ltd.
Near-Earth asteroids (NEAs) are celestial bodies whose orbits intersect with Earth’s, holding great significance for studying Solar System formation and evolution while posing potential collision hazards to humanity. However, classifying small, newly discovered NEAs remains challenging due to limited observational windows.
Led by researchers from the Purple Mountain Observatory, Chinese Academy of Sciences, the international team conducted a one-year observational campaign from October 2023 to October 2024. Using the Johnson-Cousins BVRI broadband photometric system, they collected data from two telescopes: the Purple Mountain Observatory Yaoan High Precision Telescope (YAHPT, IAU code O49) in China and the Kottamia Astronomical Observatory 1.88 m telescope (IAU code 088) in Egypt. After rigorous data reduction and analysis, the team successfully obtained photometric color indices for 84 NEAs and completed taxonomic classification for 80 of them.
The results show that nearly half (46.3%) of the sampled asteroids belong to the S-complex, 26.3% to the C-complex, 15.0% to the X-complex, and 6% to the D-complex, with the remaining classified as A-type or V-type. Statistical analysis revealed that C/X-complex asteroids are more abundant among smaller NEAs (absolute magnitude H > 17.0), accounting for nearly twice the proportion of larger ones. Additionally, X-complex asteroids tend to have sub-kilometer diameters, while C- and S-complex asteroids show similar distributions across different size ranges.
Orbital parameter analysis indicated that C/D-complex asteroids dominate NEAs with a Jovian Tisserand parameter TJ < 3.1, suggesting a potential cometary origin. Notably, NEA (385268) exhibits spectral and dynamical properties consistent with Jupiter-family comets, likely originating from the Themis family via Jupiter’s 2:1 mean-motion resonance. Among 13 potentially hazardous asteroids (PHAs) identified in the sample, C-complex and S-complex asteroids each account for 5, a finding that challenges previous assumptions and highlights new considerations for planetary defense, as C-complex asteroids are more porous, which may reduce the effectiveness of kinetic impact deflection strategies commonly used in planetary defense.
The research provides valuable data for understanding NEA origin and evolution mechanisms, while offering practical guidance for planetary defense planning. Future studies will expand the sample size, focus on fainter NEAs, and incorporate infrared observations to improve classification accuracy.
See the article:
Taxonomic classification of 80 near-Earth asteroids
http://dx.doi.org/10.26464/epp2025080
Journal
Earth and Planetary Physics
Article Title
Taxonomic classification of 80 near-Earth asteroids
Article Publication Date
31-Jan-2026
How brick-building bacteria react to toxic chemical in Martian soil
Indian Institute of Science (IISc)
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Microscopy image of Sporosarcina pasteurii
view moreCredit: Aloke Lab, IISc
Bacteria that thrive on Earth may not make it in the alien lands of Mars. A potential deterrent is perchlorate, a toxic chlorine-containing chemical discovered in Martian soil during various space missions.
Researchers at the Indian Institute of Science (IISc) recently investigated how bacteria that can mould Martian soil into brick-like structures fare in the presence of this chemical. They find that although perchlorate slows down bacterial growth, it also surprisingly leads to the formation of stronger bricks.
“Mars is an alien environment,” says Aloke Kumar, Associate Professor in the Department of Mechanical Engineering and corresponding author of the study published in PLOS One. “What is going to be the effect of this new alien environment on Earth organisms is a very, very important scientific question that we have to answer.
In previous studies, the researchers used the soil bacterium Sporosarcina pasteurii to build “space bricks” from lunar or Martian soil that can potentially be used to set up extraterrestrial habitats. When added to synthetic Martian or lunar soil along with urea and calcium, the bacterium produces calcium carbonate crystals (precipitates), which help glue the soil particles together into bricks, in a process called biocementation. The process also requires the natural adhesive guar gum, a powdery polymer extracted from guar beans.
In the current study, the authors used a more robust, native strain of the bacterium that they discovered in the soils of Bengaluru.
After first establishing its precipitate-forming skills, the researchers were curious to see if this strain can survive in the presence of perchlorate, which can be found at levels of up to 1% in Martian soils. In collaboration with Punyasloke Bhadury, Professor at the Indian Institute of Science Education and Research (IISER), Kolkata, the team found that the bacterial cells become stressed in its presence – they grow slowly, become more circular in shape, and start clumping together into multicellular-like structures. The stressed bacterial cells also release more proteins and molecules in the form of extracellular matrix (ECM) into the environment. Using electron microscopy, the researchers found that more calcium chloride-like precipitates were formed, and that the ECM formed little “microbridges” between the bacterial cells and the precipitates.
Synthetic Martian soils do not usually contain perchlorate because it is flammable, but to test its effects on biocementation, the researchers carefully added the chemical to the soil simulant in the lab. To their surprise, they found that the presence of perchlorate made the bacteria better at gluing the soil together, but only if guar gum – essential for bacterial survival – and the catalyst nickel chloride are also present.
“When the effect of perchlorate on just the bacteria is studied in isolation, it is a stressful factor,” says Swati Dubey, currently a PhD student at the University of Florida and first author of the study. “But in the bricks, with the right ingredients in the mixture, perchlorate is helping.”
Dubey thinks that the ECM microbridges could be enhancing the bacteria’s biocementation skills by funneling nutrients to the stressed cells – a theory that the team wants to explore in future studies. They also want to test the isolate’s biocementation abilities in a more Mars-like high CO2 atmosphere, which they plan to simulate in the lab.
Ultimately, the team’s goal is to deploy this method as an alternative, sustainable building strategy, to rely less on carbon-intensive cement-based processes – both on Earth and Mars. Such technologies can also help make future Mars landing missions smoother – by helping build better roads, launch pads, and rover landing sites, says co-author Shubhanshu Shukla, ISRO astronaut who is pursuing his Master’s degree with Kumar at IISc. The uneven topography of the moon’s surface, for instance, has caused some landers to topple over, he adds.
“The idea is to do in situ resource utilisation as much as possible,” Shukla says. “We don’t have to carry anything from here; in situ, we can use those resources and make those structures, which will make it a lot easier to navigate and do sustained missions over a period of time.”
Journal
PLOS One
Article Title
Effect of perchlorate on biocementation capable bacteria and Martian bricks
Article Publication Date
29-Jan-2026
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