Interstellar comet Borisov has an unexpected amount of carbon monoxide
Comet 2I/Borisov, the solar system’s second known interstellar visitor, probably hails from a planetary family that is chemically distinct from our own. During Borisov’s brief sojourn through the inner solar system, it was enveloped in its own tenuous gas cloud created as the sun baked ice on the comet’s surface (SN: 10/14/19). New observations of that gas show that the amount of carbon monoxide compared to water was off the charts — at least three times as high as any locally sourced comet that has ventured into the inner solar system. Martin Cordiner, an astrochemist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and Dennis Bodewits, planetary scientist at Auburn University in Alabama, report the findings in two papers published online April 20 in Nature Astronomy. Astronomers don’t know where Borisov came from. It was discovered in August 2019 on a trajectory tracing back to somewhere in the constellation Cassiopeia (SN: 9/12/19). Seeing a unique opportunity to get a glimpse at the chemistry of another...