Saturn’s moon Enceladus is erupting a plume of gas and ice grains from its south pole. According to new research using data from NASA’s Cassini mission, the Enceladean ice grains contain low-mass nitrogen-, oxygen-bearing, and aromatic compounds.
Dr. Nozair Khawaja from the Free University of Berlin and colleagues used data from the Cosmic Dust Analyzer (CDA) instrument on NASA’s Cassini spacecraft, which detected ice grains emitted from Enceladus into Saturn’s E ring.
The team used the CDA’s mass spectrometer measurements to determine the composition of organic material in the grains.
The identified nitrogen-bearing, oxygen-bearing, and aromatic compounds first dissolved in the subsurface ocean of Enceladus, then evaporated from the water before condensing and freezing onto ice grains inside the fractures in the moon’s crust, according to the researchers.
Blown into space with the rising plume emitted through those fractures, the ice grains were then analyzed by the CDA instrument.
“On Earth, similar compounds are part of chemical reactions that produce amino acids, the building blocks of life,” the study authors explained.
“Hydrothermal vents on the ocean floor provide the energy that fuels the reactions.”
“Enceladus’ hydrothermal vents may operate in the same way, supplying energy that leads to the production of amino acids.”
“If the conditions are right, these molecules coming from the deep ocean of Enceladus could be on the same reaction pathway as we see here on Earth.”
“We don’t yet know if amino acids are needed for life beyond Earth, but finding the molecules that form amino acids is an important piece of the puzzle,” Dr. Khawaja said.
The new findings complement the team’s discovery last year of large, insoluble complex organic molecules believed to float on the surface of Enceladus’ ocean.
“Here we are finding smaller and soluble organic building blocks — potential precursors for amino acids and other ingredients required for life on Earth,” said Dr. Jon Hillier, also from the Free University of Berlin.
“This work shows that Enceladus’ ocean has reactive building blocks in abundance, and it’s another green light in the investigation of the habitability of Enceladus,” said Dr. Frank Postberg, from Heidelberg University and the Free University of Berlin.
The results were published online this week in the Monthly Notices of the Royal Astronomical Society.
N. Khawaja et al. 2019. Low-mass nitrogen-, oxygen-bearing, and aromatic compounds in Enceladean ice grains. MNRAS 489 (4): 5231-5243; doi: 10.1093/mnras/stz2280