The Rosetta Orbiter orbiting Comet 67P detected molecular nitrogen from October 17 to 23, 2014 when the orbiter was just 10 kilometers from the comet's center using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis. These findings, published in the journal Science, could reveals clues about the formation of the Solar System.
The presence of molecular nitrogen on the comet indicates that the comet was created in freezing conditions with temperatures low enough to freeze nitrogen into ice. Since the other planets and moons in the solar system also contain nitrogen, it means that Rosetta's detection of the gas suggests that the comet was formed in the same region.
Researchers also confirmed that molecular nitrogen found on the comet was the most common type found in the nearby planetary group and is one of the primary gases found in the gas giants.
This isn't the first time nitrogen has been found on comets. But this is the first occasion that is has been distinguished by itself and as molecular nitrogen. In most cases, nitrogen is found alongside other compounds such as ammonia or hydrogen cyanide.
"Its detection is particularly important since molecular nitrogen is thought to have been the most common type of nitrogen available when the solar system was forming," ESA officials wrote in a statement.
"In the colder outer regions, it likely provided the main source of nitrogen that was incorporated into the gas planets," ESA added. "It also dominates the dense atmosphere of Saturn's moon Titan and is present in the atmospheres and surface ices on Pluto and [on] Neptune's moon Triton."
The finding also included a surprise. The ratio of molecular nitrogen to carbon monoxide was 25 times less than expected from models of the early solar system. According to scientists, this unexpectedly low ratio is probably due to the way the ice was formed. The ice most likely formed at extremely low temperatures in conditions cold enough to cause both the carbon monoxide and the molecular nitrogen to freeze causing the nitrogen to be trapped in "cagelike" water-ice known as clathrates. For this to form, temperatures were most likely between minus 418 Fahrenheit and minus 364 Fahrenheit.
Another possibility put forth by researchers is that the ice formed at a temperature of approximately minus 423 Fahrenheit which would make sense if the origins of the comet is somewhere in the vicinity of Pluto and Triton.
Regardless of the origin, the ice would melt as the comet approached the sun further explaining the low ratio, scientists said.
