For quite some time, an asteroid named Phaethon has presented astronomers with something of a conundrum.
When it passes closest to the sun during its orbit, a protracted tail of fabric may be seen leaving the three-mile-wide (five-kilometer-wide) rock. Nonetheless, if Phaethon’s tail is the stuff of usual comets — ice and carbon dioxide — then it needs to be visible when the comet is as distant as Jupiter, too. However it’s not.
Scientists have subsequently had some theories about what Phaethon is likely to be composed of, which could explain what trails behind when the asteroid passes by the Sun. And in recent research, astronomers have compared the infrared emissions of Phaethon analyzed by NASA’s Spitzer space telescope to emissions of meteorites in laboratories, ultimately finding that Phaethon likely belongs to a rare class of meteorite, of which only six specimens are known.
Related: The strange mystery of asteroid Phaethon’s comet-like tail
Namely, Phaethon’s emission spectrum corresponds to a sort of meteorite called the “CY carbonaceous chondrite.” Conversely, other well-known asteroids comparable to Ryugu and Bennu, targets of the recent JAXA and NASA sample-return missions, are CI and CM meteorites respectively.
All three classes of meteorites are believed to have originated in the course of the birth of the solar system, as all of them show signs of the chemical process through which water combines with other molecules to form phyllosilicate and carbonate materials. Nonetheless, only the CY group appeared to show signs of drying and decomposition resulting from heating; it also exhibits a high iron sulfide content, which suggests a novel origin.
Analyses of Phaethon’s emission spectrum revealed olivine, carbonates, iron sulfides and oxide minerals — all of which supported the space rock’s connection to the CY class of asteroid. Carbonates within the asteroid indicate changes in water content (the drying), as an illustration, and the olivine is consistent with thermal decomposition of phyllosilicates at high temperatures.
Researchers were in a position to show with thermal modeling how temperatures, comparable to those encountered when passing by the sun, might affect minerals within the asteroid that release gases. Because the asteroid gets nearer the searing ball of plasma at our solar system’s center, its surface temperatures can rise to 800°C, which the team says is definitely hot enough for the item’s carbonates to provide carbon dioxide, phyllosilicates to release water vapor and sulfides sulfur gas.
Data from other studies on asteroids, combined with the brand new thermal models of Phaethon, led the researchers to consider that pressure from the gas released by the asteroid heating up could cause the rock to interrupt down, producing small dust particles which can be lifted from its surface — a possible explanation for Phaethon’s tail because it passes by the sun.
“It was great to see how each certainly one of the discovered minerals appeared to fall into place and in addition explain the behavior of the asteroid,” said co-author Mikael Granvik from the University of Helsinki, in a press release.
The research was published in November within the journal Nature Astronomy.