The European Space Agency (ESA) revealed that scientists have finally detected molecular nitrogen on comet 67P/Churyumov-Gerasimenko, the target object of ESA's Rosetta spacecraft. The discovery is crucial in that it could shed light on the conditions that paved the way for the formation of the solar system.
Molecular nitrogen is believed to be the most common type of nitrogen present during the formative period of the solar system. In the colder outer regions, it is thought that molecular nitrogen provided the primary source of the chemical element that was incorporated into gas planets. Molecular nitrogen is also present in the atmospheres of Saturn's moon Titan, Neptune's moon Triton, and also in Pluto.
"Identifying molecular nitrogen places important constraints on the conditions in which the comet formed, because it requires very low temperatures to become trapped in ice," said Martin Rubin from the University of Bern, one of the researchers who presented the results based on 138 measurements gathered by Rosetta's ROSINA mass spectrometer from Oct. 17 to 23 when the spacecraft was approximately 10 kilometers way from the center of comet 67P/Churyumov-Gerasimenko.
It turned out that the ratio of molecular nitrogen to carbon monoxide for comet 67P/Churyumov-Gerasimenko was about 25 times less than the expected value from models of the early solar system.
Scientists said that the low ratio could be attributed to the way ice was formed at extremely low temperatures with the molecular nitrogen possibly trapped inside cage-like water ice known as clathrates between minus 418 Fahrenheit and minus 364 Fahrenheit. Another possibility was that the ice could have trapped the molecular nitrogen at about minus 423 Fahrenheit in the same region of the solar system as Triton and Pluto, which could explain these extraterrestrial worlds' relatively nitrogen-rich ices.
Scientists said that the comet would have released the nitrogen as it got closer to the solar system, causing the ice on the comet to melt and which could explain the low ratio.
"We report the direct in situ measurement of N2 in the Jupiter family comet 67P/Churyumov-Gerasimenko made by the ROSINA mass spectrometer aboard the Rosetta spacecraft," Rubin and colleagues wrote in their study published in the journal Science on March 19. "A N2/CO ratio corresponds to depletion by a factor of ~25.4 ± 8.9 compared to the protosolar value. This depletion suggests that cometary grains formed at low temperature conditions below ~30 K."