Enceladus, Saturn’s walnut-shaped moon, contains complex organic molecules within its oceans, according to research published Wednesday in Nature, further distinguishing the celestial entity as one of the most likely worlds to host alien life in the solar system.
The study, led by Frank Postberg and Nozair Khawaja of the University of Heidelberg, is based on data collected by NASA’s Cassini orbiter before it plunged into Saturn in September 2017 (RIP).
The carbon-rich “macromolecules” identified by the study are an essential ingredient in life as we know it on Earth. These are the types of versatile chemical foundations that enabled living creatures to evolve on Earth.
During its twilight years, Cassini was able to directly sample Enceladus’ ocean by scooping up ice grains that the moon sprayed into space in geyser-like plumes. The orbiter used its Cosmic Dust Analyzer (CDA) and Ion and Neutral Mass Spectrometer (INMS) instruments to measure the chemical composition of the material, and relayed that information back to Earth.
Initial analysis of this data picked up simple organic molecules, and also detected an abundance of molecular hydrogen. These readings suggest that the rocky floor of Enceladus’ subsurface ocean may feature hydrothermal reactions, similar to those observed at Earth’s deep sea vents.
These habitats can host lush ecosystems supported by “methanogens,” lifeforms that convert carbon dioxide and molecular hydrogen into methane, and similar organisms potentially exist on Enceladus. In the latest analysis of Cassini’s data, Postberg and Khawaja’s team identified macromolecules from this alien ocean that exceed 200 atomic mass units—ten times heavier than methane.
It would be premature to whip out your “first contact” celebratory gear at this stage, however. We’ll need to launch another spacecraft to Saturn to know for sure if Enceladus is filled with tiny alien beasties, as Cassini wasn’t equipped to explicitly detect life. Several concept missions, such as the aptly named Enceladus Life Finder (ELF), have been proposed for this purpose but none have been greenlit yet.
That’s why this paper has “great significance for the next generation of exploration," according to coauthor Christopher Glein, a space scientist at the Southwest Research Institute.
"A future spacecraft could fly through the plume of Enceladus, and analyze those complex organic molecules using a high-resolution mass spectrometer to help us determine how they were made,” he said. “We must be cautious, but it is exciting to ponder that this finding indicates that the biological synthesis of organic molecules on Enceladus is possible."
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