Comets can be very strange. And they are constantly striving to take on more bizarre outlines.
Take for example the comet 67P / Churyumov-Gerasimenko. This piece of stone and ice, 3 miles wide, entered the European Rosette orbit in September. Its smell is terrible, its sound is reminiscent of a strange song that sounds on radio waves, its color is much darker than coal, which is absolutely not in line with preliminary expectations.
However, now scientists from NASA's Jet Propulsion Laboratory (JPL) and the California Institute of Technology (Caltech) in Pasadena (California) have identified another feature of comets from the “strange list”. It is a form resembling an ice cream spatula.
“The comet bark consists of crystalline ice, and its interior is more porous and cold,” said Murta Gadpate, a member of the Jet Propulsion Laboratory, a co-author of a recent study, the results of which are published in The Journal of Physical Chemistry. “Organics can be compared with the final layer of chocolate at the very top of the ice cream.”
A group of researchers from Caltech under the leadership of Antti Linell conducted a series of unusual experiments. In particular, they used the Himalayan laboratory freezer, which was used to reproduce the conditions for the formation of ice on a comet in outer space. It was found that the fluffy ice on the surface of the comet crystallizes and hardens as the comet approaches the Sun. These findings are announced in a NASA press release. During the formation of an ice-water crystal, other carbon molecules that are contained in excess in space create a crisp crust with a thin layer of organic materials.
In their laboratory experiments, Linell and Gadpate studied how water vapor is mixed with molecules of other substances present on the surface of comets. These include polycyclic aromatic hydrocarbons or PAHs. Fast freezing to a temperature of 30 degrees Kelvin (-243˚C or -405 degrees Fahrenheit) is impossible in the natural conditions of the Earth. However, in space, these processes are not interrupted for a minute. Water vapor instantly freezes, forming “amorphous ice” - a light, fluffy, porous substance resembling hard cotton candy or airgel (“frozen smoke”).
To imitate the processes occurring on a comet as it approaches the Sun, Linell and Gadpate heated the mockup of the comet to 150 degrees Kelvin (-123˚C or -190 degrees Fahrenheit). This made it possible to model several very interesting chemical reactions.
“During the heating, the ice began to actively crystallize, expelling PAH particles from itself,” Lynell said. “Perhaps here we are the first to observe clustering molecules at the time of the ice phase transition. Of course, this discovery is of great importance for the physics and chemistry of ice. ”
“What we see in the laboratory — the crystalline crust of a comet with the upper organic layer — fully corresponds to the models that were built in the process of observing outer space,” Gadpate noted. “The most accurate metaphor will be“ hot ice cream ” since the temperature of the amorphous ice inside the comet is extremely low, and its structure has a characteristic porous character. ” When comparing all the conducted research and experiments, unequivocal conclusions were made that the internal matter of the comets is constituted by porous ice, while the surface of cosmic bodies is lined by a crystallized crust. In addition, these experiments allowed us to get an idea of the organic history of our planet. It is believed that it was the comets that brought to Earth the substances necessary for the emergence of life. That is why the study of substances in cometary nuclei will allow with a certain accuracy to establish the mechanisms of the appearance of organic life on our planet.
“It is so nice to think about how far we have come in understanding the essence of comets. Future missions are being developed in order to deliver samples of cometary cold matter to Earth. This will allow us to fully reveal the sextets of cosmic life, ”Gadpade concluded.