Red asteroids near Neptune hold clues to early solar system.

Astronomers have found that the asteroids orbiting near Neptune are far redder than most asteroids in the solar system, indicating that they are rich in volatile compounds such as ammonia and methanol. Researchers tracked 18 Neptunian Trojans and analyzed their color, finding that most were significantly redder than most asteroids, including four that were extremely red. Studying these asteroids could reveal how asteroids in the early solar system formed and how their composition has changed over the past 4.6 billion years.