An international team of astronomers led by University of Arizona scientist Dr. Vishnu Reddy has obtained observations of the smallest near-Earth asteroid (NEA) ever characterized in detail.
An artist’s impression of a near-Earth asteroid. Image credit: NASA / JPL-Caltech.
The asteroid, named 2015 TC25, is only 6 feet (2 m) in diameter. It was discovered in October 2015 by astronomers with the NASA-funded Catalina Sky Survey.
Interestingly, 2015 TC25 is also one of the brightest NEAs ever discovered — the object reflects about 60% of the sunlight that falls on it.
In a paper published in the Astronomical Journal, Dr. Reddy and his colleagues from Canada and the United States argue that new observations from NASA’s Infrared Telescope Facility and Arecibo Planetary Radar show that 2015 TC25’s surface is similar to a rare type of highly reflective meteorite called an aubrite.
Aubrites consist of very bright minerals (mostly silicates) that formed in an oxygen-free, basaltic environment at very high temperatures.
“2015 TC25’s surface composition is similar to aubrites, a rare class of high-albedo differentiated meteorites,” the researchers said.
“Aubrites make up only 0.14% of all known meteorites in our terrestrial meteorite collection.”
Small NEAs such as 2015 TC25 are in the same size range as meteorites that fall on Earth.
Astronomers discover them frequently, but not very much is known about them as they are difficult to characterize.
By studying such objects in more detail, they hope to better understand the parent bodies from which these meteorites originate.
“It’s especially important to study the physical properties of small NEAs because of the threats these objects pose to us,” said co-author Prof. Stephen Tegler, of Northern Arizona University.
“If we can discover and characterize asteroids and meteoroids this small, then we can understand the population of objects from which they originate: large asteroids, which have a much smaller likelihood of impacting Earth,” Dr. Reddy added.
“In the case of 2015 TC25, the likelihood of impacting Earth is fairly small.”
The discovery also is the first evidence for an asteroid lacking the typical dust blanket — called regolith — of most larger asteroids. Instead, this object consists essentially of bare rock.
Probably, 2015 TC25 is what planetary researchers call monolithic, meaning it is more similar to a ‘solid rock’ type of object than a ‘rubble pile’ type of object like many large asteroids.
The astronomers also found that 2015 TC25 is one of the fastest-spinning NEAs ever observed, with a period of 133 s.
They believe 2015 TC25 was chipped off by another impacting rock from its parent, (44) Nysa, a large and bright main-belt asteroid that measure 44 miles (70 km) in diameter.
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Vishnu Reddy et al. 2016. Physical Characterization of 2 m Diameter Near-Earth Asteroid 2015 TC25: a Possible Boulder from E-Type Asteroid (44) Nysa. AJ 152, 162; doi: 10.3847/0004-6256/152/6/162
