The comet is unique - not only was it made of carbon dioxide, but it had a carbon dioxide ice-to-water ice ratio that was literally out of this world, 8:1, which is among the highest ever recorded.
The speed and trajectory of 3I/ATLAS suggest that it comes from the thick disk of the Milky Way, the puffy region around the thin disk wherein just 15 percent of the galaxy's stellar mass resides.
Astronomers on Wednesday confirmed the discovery of an interstellar object racing through our solar system - only the third ever spotted, though scientists suspect many more may slip past unnoticed.
