Last fall, when the notorious Cbadini spacecraft was spiraling toward its final and fatal descent into the clouds of Saturn, the astrochemist Morgan Cable could not help but shed a tear for the orbiter the size of the school bus, which He became a victim of his own success.
Early in his mission, as he flew over Saturn's ice-covered moon Enceladus, Cbadini discovered jets of ice and salt water coming out of cracks in the south pole, a sign that the body contained an underground ocean that It could hold life. When the orbiter began to run short of fuel, it crashed into Saturn instead of risking a whimsical plunge that would contaminate the potentially habitable world.
Now, from beyond the grave, the spacecraft has offered another prize for scientists. A new badysis of the Cbadini data suggests that these frozen feathers that shoot into space contain complex organic compounds, the building blocks essential to living things.
The fact that an aging orbiter not designed for life detection has been able to detect these molecules, which are among the largest and most complex organic compounds found in the solar system, which turns the frozen moon into an even more tempting target in the search for extraterrestrial life, said Cable, a research scientist at the Jet Propulsion Laboratory who was not involved in the new research. .
"This is a powerful study with a powerful result," he said.
The findings published Wednesday in the journal Nature are based on data collected by two Cbadini instruments: the Cosmic Dust Analyzer and the Ionic and Neutral Mbad. Spectrometer – when the spacecraft flew through the outermost ring of Saturn and the feathers of Enceladus (pronounced "in-BAND-a-dus").
Previous research using these instruments has detected a small orga nic molecules such as methane, which consists of four hydrogen atoms attached to a single carbon. The INMS has also detected molecular hydrogen, a chemical characteristic of hydrothermal activity that provides an important fuel for the microbes that live around Earth's vents.
The molecules reported in the new Nature paper are "orders of magnitude" larger than any seen before, according to lead author Frank Postberg, a planetary scientist at the University of Heidelberg in Germany. There were stable carbon ring structures known as aromatics, as well as chains of carbon atoms attached to hydrogen, oxygen and even nitrogen.
Some of the molecules detected by the CDA were so large that the instrument could not badyze them. This suggests that the organic compounds that Cbadini found are only fragments of even larger compounds, Postberg said. There may be large polymers, many segmented molecules, such as those that make up DNA and proteins, which are still waiting to be discovered.
"Astrobiologists get excited about bigger molecules and that sort of thing because it means that something is building on itself and getting more complex," said Kate Craft, planetary scientist at the Applied Physics Laboratory at Johns Hopkins University who did not participate in the investigation.
The molecules that Cbadini has detected can be produced abioticly, without the participation of life. But they are also the kind of compounds that microbes on Earth like to eat, and could even be byproducts of microbial metabolism.
"Put it this way, if you did all these tests and you did not see these larger molecules, [Enceladus] does not seem to be habitable," Craft said. "But these findings … are a reason to say: 'Hey, we have to go back and take a lot more data.'"
Scientists believe that Saturn's gravitational influence tightens and flexes the rocky material porous in the core of Enceladus, generating heat. That heat allows chemical interactions between the salty ocean and the seabed. On Earth, such water-rock interactions provide fuel for the chemotrophs – organisms that obtain energy by decomposing chemicals in their environments – and support vast ecosystems in the deepest and darkest depths of the ocean.
Postberg and his colleagues propose that the organic molecules generated in the ocean depths of Enceladus finally float to the surface, where they form a thin film just below the icy crust of the planet.
Earth's oceans are covered by a similar film, they point out: a mantle of tiny microbes one millimeter thick. organic matter that serves as an important interface between the sea and the sky. Research shows that this layer helps to conduct the climate; When the bubbles explode when the waves break, the particles of the film rise into the air, where they provide a nucleus around which the water condenses to form clouds and fog.
A similar process on the ocean surface of Enceladus can form ice crystals with the organics in its core, Postberg said. These grains are sucked up through cracks in the lunar crust called "tiger stripes" and then thrown into the void of space.
Enceladus feathers are extremely faint, more like a thin veil than a jet of a fire hose, and scientists have questioned whether a spacecraft flying through the aerosol would be able to collect enough organic elements to draw conclusions about its origin.
This result, said Postberg, shows that Enceladus "is kind to us and delivers his organic inventory in high concentrations to space."
Cable is a project scientist attached to a concept called Enceladus Life Finder, which would use instruments more advanced than Cbadini's to sample the pen during a series of overflights. The mission has not been funded by NASA, and the space agency has no projects in development to return to Enceladus.
She, Postberg and Craft expressed the hope that this latest find will generate interest in a new mission to the frozen moon. 19659002] "Enceladus shouts at us that it has all the ingredients for life as we know it: water, chemical, organic," Cable said. "We have to go back."