New Type of Comet Discovered

Credit: ESO/M. Kornmesser

We all know what comets are. There may be some variation between each one, some are bigger and more pristine than others, and some put on a spectacular show as they sail past the Earth. But they're all basically "dirty snowballs". Comets are mostly ice, with some rock mixed in. As the comet falls closer to the sun, the ice begins to vaporize, forming a tail that can stretch for millions of miles behind it. They're all the same because they come from the same basic place. Sure, there may be half a light year between the Kuiper Belt and the outer Oort Cloud, but there's not a whole lot of difference in the materials in an Oort Cloud comet and a Kuiper Belt comet. They're all big interplanetary icebergs left over from the formation of the solar system. At least, they were. Not anymore.

To be honest, it's almost cheating to call Comet C/2014 S3 an actual comet. It has a 860 year long orbit, which is very comet-like, it enters the inner solar system like a comet, but it has very little ice and has a very minimal tail. An analysis of the limited dust from the comet's tail revealed that the comet is mostly made of rock. That makes it more of an asteroid than a comet. Indeed, the astronomers who discovered S3 theorize that the comet is actually from the inner Solar System, but was flung outwards early on in the formation of the solar system by some larger body. Comet S3 might be one of the most well-preserved relics of the formation of the rocky inner planets in the entire solar system. It's spent most of its time floating in the cold of the Oort Cloud, away from the harshest portion of the solar wind. Finding more objects like this comet would give clues as to how exactly the solar system was created, specifically how much material was in the early inner solar system.