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Enceladus water feathers contain life clues | Space



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The steam columns of Enceladus. Image via NASA / JPL / Space Science Institute.

Saturn's moon, Enceladus, may be small, but it has the potential to help answer one of the most important questions in history: are we alone? The NASA Cassini mission studied this enigmatic world closely and discovered that it is incredibly active, at least geologically, with huge plumes of water vapor rising through huge cracks in the surface, from a salty subsurface ocean beneath the crust outside of ice. Cassini actually flew through those feathers and took them to analyze them. We already knew that he found water vapor, ice particles, salts, hydrogen and simple organic compounds. Now, a new analysis from the Southwest Research Institute (SwRI) published on June 27, 2018, shows that feathers also contain much more complex organic compounds. This does not mean evidence of life itself, however, but it shows more clearly that the ocean of Enceladus meets all the requirements for life to exist.

The research team was led by Frank Postberg and Nozair Khawaja of the University of Heidelberg, Germany. As Postberg pointed out:

It is the first detection of complex organic elements from an extraterrestrial aquatic world.

Diagram of rich organic bubbles that rise to the surface from the depths of the ocean. Image via ESA / F. Postberg et al (2018).

Diagram representing the interior of Enceladus. The ocean water below, along with the organic matter, reaches the surface through cracks in the outer layer of ice. Image via NASA / JPL-Caltech / Space Science Institute / LPG-CNRS / Nantes-Angers / ESA.

The organic compounds are quite large and complex, as Khawaja added:

We found large molecular fragments that show typical structures for very complex organic molecules. These huge molecules contain a complex network often constructed from hundreds of carbon, hydrogen, oxygen and probably nitrogen atoms that form ring and chain substructures.

SwRI scientists analyzed Cassini mass spectrometry data. As explained by Dr. Christopher Glein, a space scientist specializing in extraterrestrial chemical oceanography (and co-author of the new article in the scientific journal Nature ):

We are, once again, impressed far away by Enceladus. Previously we had only identified the simplest organic molecules that contained some carbon atoms, but even that was very intriguing. Now we have found organic molecules with masses greater than 200 atomic mass units. That's more than ten times heavier than methane. With complex organic molecules emanating from its ocean of liquid water, this moon is the only body besides the Earth that simultaneously satisfies all the basic requirements for life as we know it.

Diagram of an internal cross-section of the Enceladus crust, showing hydrothermal vents at the bottom of the ocean and columns of water vapor that erupt through cracks in the surface. Image via NASA-GSFC / SVS / NASA / JPL-Caltech / Southwest Research Institute.

It is believed that the heavy organic fragments discovered are remnants of even thousands of larger units of atomic mass. The larger ones were divided into smaller fragments when they collided with the Cassini dust analyzer at speeds of approximately 18,640 miles per hour (30,000 kilometers per hour). Such large organic molecules can only be created by complex chemical processes, including life or hydrothermal activity.

The discovery of such complex organic compounds is exciting, especially when they are found in an ocean of warm water. Organics like this can be formed abiotically, without life, or they can be relics of organisms themselves. In the case of Enceladus, we do not know which one is still, or both, but it is tempting. There is also evidence of Cassini for active hot geothermal vents at the bottom of the ocean, such as on Earth. Here, such vents are filled with a variety of small organisms. Could it be the same for Enceladus? The Cassini mission itself may be over now, but the science continues, as Glein points out:

Even after its end, the Cassini spacecraft continues to teach us about Enceladus' potential to advance in the field of astrobiology in a world oceanic. This document demonstrates the value of teamwork in planetary science. The INMS and CDA teams collaborated to arrive at a deeper understanding of the organic chemistry of the Encelado subsurface ocean than would be possible with a single data set.

The molecular hydrogen previously detected in feathers is another important clue, as it is thought to be formed by geochemical interactions between water and rocks in hydrothermal environments. According to Dr. Hunter Waite of SwRI, principal investigator of INMS and co-author of the new article:

Hydrogen provides a chemical energy source that sustains microbes living in Earth's oceans near hydrothermal vents. Once you have identified a possible source of food for the microbes, the next question is "what is the nature of complex organic compounds in the ocean?" This document represents the first step in that understanding: complexity in organic chemistry exceeds our expectations!

The results also suggest a thin "film" rich in organic matter in the upper part of the ocean. Bubbles of gas, which rise upward through tens of miles of ocean water, could bring in organic material where they form a thin film floating on the surface of the ocean just below the outer layer of ice. From the summary:

Here we report observations of emitted ice grains containing concentrated and complex macromolecular organic material with molecular masses greater than 200 atomic mass units. The data limit the macromolecular structure of the organics detected in the ice grains and suggest the presence of a thin film rich in organic compounds on the oceanic water table, where the organic nucleation nuclei generated by the explosion of bubbles allow probing the organic inventory of Enceladus. in improved concentrations.

A global vision of Enceladus. Image via NASA / JPL / Space Science Institute.

These findings are not only exciting in themselves, but also have implications for the future exploration of Enceladus, and the concepts of return mission are now on the drawing boards. As Glein pointed out:

The document's findings are also very important for the next generation of exploration. A future spacecraft could fly through the Enceladus pens and analyze those complex organic molecules using a high-resolution mass spectrometer to help us determine how they were made. We must be cautious, but it is exciting to think that this finding indicates that the biological synthesis of organic molecules in Enceladus is possible.

Conclusion: Thanks to Cassini, Enceladus has long been considered one of the best places in the world. solar system to look for evidence of extraterrestrial life. Is there something swimming in that warm but dark ocean? Perhaps, and this new discovery of complex organic compounds strengthens the possibility. Even if it's just something like bacteria, finding life in the ocean of Enceladus would be one of the most exciting discoveries in history.

Source: macromolecular organic compounds from the depths of Enceladus

SwRI / Via ESA

  Paul Scott Anderson

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