It is a known fact for scientists that Comet 67P/Churyumov-Gerasimenko lacks nitrogen. Back in 2014, ESA’s Rosetta spacecraft measured the gases in a comet’s coma after its ten years of traveling toward it. The question is: Why is the comet so low in nitrogen gas?
According to two new studies shared in Nature Astronomy, the nitrogen is concealed in the building blocks of life; therefore, they are not low at all. Rosetta spacecraft lasted for two years on its mission before crashing into the Comet 67P. The probe also unsuccessfully released a lander, which crippled when it landed on the comet’s surface. However, it was still able to take a few images.
After Rosetta’s mission three years ago, the scientists are still studying the data collected by the spacecraft. “Although Rosetta operations ended over three years ago, it is still offering us an incredible amount of new science and remains a truly ground-breaking mission,” said Matt Taylor, ESA’s Rosetta Project Scientist.
The first new study
The first modern study is based on observations using Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA). Comets are an icy, small Solar System body, while the coma is a “fuzzy” appearance that a comet gets when it passes close to the Sun. The Comet’s 67P coma was analyzed by Rosetta and was found to contain a reasonable amount of chemicals such as oxygen and carbon, but lacked nitrogen.
“The reason behind this nitrogen depletion has remained a major open question in cometary science,” said Kathrin Altwegg of the University of Bern, Switzerland, principal investigator for the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument and lead author of a new study. “Using ROSINA observations of Comet 67P, we discovered that this ‘missing’ nitrogen might, in fact, be tied up in ammonium salts that are difficult to detect in space. Finding ammonium salts on the comet is hugely exciting from an astrobiology perspective,” she added in a press release.
The molecular panspermia theory
The molecular panspermia theory is an old idea that refers to a comet’s building blocks of life as having a crucial role in spreading them throughout the Solar System. Rosetta discovered both glycine and phosphorus in 67P’s coma in 2016, which kind of proves that the theory is correct. It is believed that the comet’s containing those blocks of life, bombarded our planet to bring water on it, in the Earth’s early days. According to the theory, the blocks of life are forged in space and spread to planets via comets and asteroids.
“Finding ammonium salts on the comet is hugely exciting from an astrobiology perspective,” said Altwegg. “This discovery highlights just how much we can learn from these intriguing celestial objects.”
The second new study
The second new study is based on observations using Rosetta’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument. Their research brought to light the first organic compounds ever found on the surface of a comet’s nucleus. Aliphatic organic mixtures were discovered for the first time on the Comet 67P, which are chains of hydrogen and carbon that also build blocks of life.
“Where – and when – these aliphatic compounds came from is hugely important, as they are thought to be essential building blocks of life as we know it,” explained the lead author is Andrea Raponi of INAF, the National Institute for Astrophysics in Italy. “The origin of material such as this found in comets is crucial to our understanding of not only our Solar System but planetary systems throughout the Universe,” she added.
Is the molecular panspermia theory confirmed?
These organic mixtures that form blocks of life are not originated from the comet itself. They were created in a solar nebula, an early formed Sun or in the interstellar medium, said scientists in this new study. “Inspiring discoveries such as these help us to understand a great deal more about not only comets themselves, but the history, characteristics, and evolution of our entire cosmic neighborhood,” said Taylor.
This second study also shows the strong compositional similarities between 67P and other carbon-rich objects outside the Solar System. “We found that the nucleus of Comet 67P has a composition similar to the interstellar medium, indicating that the comet contains unaltered presolar material,” says study co-author Fabrizio Capaccioni, also of INAF and principal investigator for VIRTIS. “This composition is also shared by asteroids and some meteorites that we have found on Earth, suggesting that these ancient, rocky bodies locked up various compounds from the primordial cloud that went on to form the Solar System.”
He also added that “This may mean that at least a fraction of the organic compounds in the early Solar System came directly from the wider interstellar medium – and thus that other planetary systems may also have access to these compounds.”
Rosetta is not the only spacecraft that crushed ending its mission. Cassini spacecraft ended its mission over two years ago when its trajectory took it into Saturn’s upper atmosphere burning it up. Scientists are still using the data from both cases, and papers continue to be published. There is so much information from the data collected from the probes that researchers can conduct new different studies.
“Although Rosetta operations ended over three years ago, it is still offering us an incredible amount of new science and remains a truly ground-breaking mission,” adds Taylor. “These studies tackled a couple of open questions in cometary science: why comets are depleted in nitrogen, and where comets got their material from. Inspiring discoveries such as these help us to understand a great deal more about not only comets themselves, but the history, characteristics, and evolution of our entire cosmic neighborhood.”