Even though we—and the technology we create—are getting better at identifying asteroids and dwarf planets, there may be another unexpected hurdle: camouflage.
Upon reviewing information harvested by SOFIA (Stratospheric Observatory for Infrared Astronomy), the world’s largest flying observatory—basically, a plane with an awesome telescope—NASA astronomers learned that the composition of an asteroid’s exterior doesn’t necessarily match that of its interior.
Ceres. Credit: NASA
Astronomers got their first glimpse of this cosmic camouflage by examining data about Ceres, a dwarf planet (and asteroid) located in the asteroid belt between Mars and Jupiter. Astronomers classified Ceres as a “c-type” asteroid, which means that in addition to being dark in color and common in the outer solar system, it contains a lot of carbon. However, mid-infrared data from SOFIA doesn’t match that description—Ceres’ surface doesn’t actually contain much carbon at all.
The outside of Ceres is covered with interplanetary dust particles (IDP), particularly a silicate called pyroxene, a mineral common in metamorphic and igneous rocks. Researchers believe that ancient asteroid collisions that released this material, which then coated Ceres’ exterior, changing its color to resemble that of neighboring asteroids.
Credit: Pierre Vernazza, LAM–CNRS/AMU
“Seeing is not believing when it comes to asteroids…”
The findings prove that an asteroid’s surface doesn’t necessarily indicate its composition, which is significant for a number of reasons. Situations in which a body’s outer layer doesn’t match its inner composition could indicate the possibility of migration—it’s possible that Ceres first formed on the outskirts of the solar system, but gravitated inward over time. It also demonstrates the singular utility of an instrument such as SOFIA, without which astronomers would assume that Ceres’ designation as “c-class” tells the whole story.
Ceres. Credit: NASA
The ability to use mid-infrared and other techniques to examine an asteroid or planet could help prevent cases of mistaken identity when celestial bodies masquerade as something else.
“Seeing is not believing when it comes to asteroids,” says SETI astronomer Franck Marchis. “We shouldn’t judge these objects by their covers, as it were.”