#United States #Flagstaff #Lowell Observatory #Near-Earth Asteroids #Planetary Defense

New Insights into Near-Earth Asteroids: Understanding Their Compositions

A groundbreaking study has shed light on the significantly different compositions of small near-Earth asteroids (NEAs) compared to their larger counterparts. Conducted by an international team of planetary scientists led by Dr. Nick Moskovitz from Lowell Observatory, the research highlights a size-dependent trend that may reshape our understanding of meteorite origins and impact-risk assessments for Earth.

The Scope of the Study

The study involved an analysis of 189 NEAs, utilizing over a decade of data collected from the Mission Accessible Near-Earth Object Survey (MANOS) between 2014 and 2025. Key observations were achieved using three major 4-meter-class telescopes – the Lowell Discovery Telescope in Arizona, the SOAR Telescope in Chile, and the Mayall Telescope at Kitt Peak National Observatory. These facilities aided in categorizing the asteroids based on how they reflect sunlight at four distinct wavelengths, a crucial factor for assessing the surface colors of these celestial bodies.

Special attention was paid to correcting brightness variations caused by the asteroids' rotation, which significantly impacts color measurements. Dr. Moskovitz emphasized the importance of this correction, explaining how overlooking these brightness changes could lead to misleading results. “If you don’t account for how an asteroid brightens and dims as it spins, you can end up with misleading colors,” he noted.

Key Findings

The study revealed a clear trend among S-complex asteroids, which closely resemble the ordinary chondrites—commonly found in meteorite collections. It was discovered that while S-complex NEAs make up approximately 65% of those at kilometer scales, they constitute only one-third of those measuring less than 50 meters. The research explored various potential explanations for this size-dependent trend, such as solar heating and tidal resurfacing during close encounters with Earth. Surprisingly, none provided a complete explanation.

Instead, the findings align with recent models indicating that small NEAs largely originate from a limited number of young asteroid families located in the Main Belt, which possess compositions that differ from those of larger NEAs. “This is one of the clearest pieces of evidence yet that the smallest NEAs come from a different mix of sources,” Dr. Moskovitz stated, underscoring its significance in understanding why meteorites that reach Earth don’t perfectly match the larger asteroids we observe.

Practical Implications

Beyond the scientific advances, the findings also hold practical implications, especially for impact-risk assessment. With small NEAs being the objects most likely to enter Earth’s atmosphere, recognizing their compositions is vital. Understanding these materials allows scientists to model how they would behave upon atmospheric entry, thus informing potential risks posed by objects that could impact the planet’s surface.

The comprehensive study was published in the Planetary Science Journal on April 23, 2026. As noted by Dr. Moskovitz, gaining insights into the makeup of small NEAs is critical for planetary defense strategies moving forward.

About Lowell Observatory

Founded in 1894, Lowell Observatory, located in Flagstaff, Arizona, is a celebrated nonprofit research institution known for its pioneering contributions to astronomy, including the discovery of Pluto. Today, astronomers at Lowell engage in diverse astronomical and planetary science research using a combination of global telescopes and NASA spacecraft. The observatory welcomes over 100,000 visitors annually, offering educational tours and interactive telescope viewing experiences.

This study represents a significant advancement in our understanding of small NEAs and their varied origins, laying important groundwork for future research and planetary defense initiatives.