A group of Finnish astronomers from the University of Helsinki has studied the composition of the asteroid Phaethon for the first time, linking its makeup to the meteor showers that illuminate Earth’s skies each year. The findings were published in Nature Astronomy.
Asteroid Phaeton, about five kilometers across, has long intrigued scientists. As it nears the Sun, it develops a tail that resembles the tails of comets. When the surface layer breaks apart, the released dust and gravel stay in the same orbit, and when they intersect Earth’s path, they feed the Geminid meteor shower in mid-December.
Finnish researchers analyzed the infrared spectrum of Phaeton, using prior data collected by the Spitzer Space Telescope, and compared it with spectra from various meteorites.
The analysis revealed that Phaeton’s spectrum is closely aligned with the rare CY carbonaceous chondrite meteorites, a type of material that today is known from only a handful of confirmed objects.
In terms of composition, Phaeton contains olivine, carbonates, iron sulfides, and oxide minerals. The carbonate minerals show sensitivity to water content, while olivine provides evidence of thermal processing of layered silicates at very high temperatures.
According to the study, all detected minerals in Phaethon correspond to those found in CY-type meteorites, with two exceptions: portlandite and brucite oxides. These oxides have not been observed in meteorites, but they can form through heating and disintegration of carbonates in a water-vapor environment.
The researchers combined experimental data from other studies with their thermal models to estimate that near its closest approach to the Sun, gas could be released from the asteroid’s mineral network, potentially causing rock to fracture.
They also suggested that the pressure generated by carbon dioxide and water vapor could be sufficient to loft fine dust particles from Phaeton’s surface.
One of the study’s authors, Eric McLennan, noted that sodium emissions might account for the faint tail observed near the Sun, while thermal weathering could explain how dust and gravel are expelled from the asteroid.
Earlier observations had hinted at asteroids with unusual elemental signatures, sparking ongoing investigations into how such bodies form and evolve within the solar system.