A recent analysis of archival data from NASA’s Galileo spacecraft’s Near Infrared Mapping Spectrometer (NIMS) has uncovered the first evidence of ammonia-containing compounds on Jupiter’s icy moon Europa. This groundbreaking discovery provides vital clues about Europa’s subsurface ocean and recent geological activity.
This composite image highlights red pixels indicating sites on Europa where ammonia compounds were detected; purple indicates areas without detection. Image credit: NASA/JPL-Caltech.
“The detection of ammonia (NH3) is significant for understanding not only the geology of icy bodies in our solar system but also their potential habitability and astrobiological relevance,” stated Dr. Al Emran, a researcher at NASA’s Jet Propulsion Laboratory.
“On Europa, the identification of ammonia or ammoniated species is crucial for revealing ocean chemistry, assessing habitability, and reconstructing the moon’s early atmosphere.”
Ammonia functions as an antifreeze agent, reducing the freezing point of liquid water by up to 100 K, which may help preserve underground oceans in icy celestial bodies.
Though it’s unclear if Europa’s underground ocean is directly linked to the surface, detecting ammonia compounds could imply such a connection, given that these materials are unstable under cosmic radiation.
In a new study published in Planetary Science Journal, Dr. Emran reported detecting a distinct ammonia absorption feature at 2.20 microns in Europa’s near-infrared spectrum.
This signal was confirmed through observations from Galileo’s NIMS instrument, which examined Europa during a flyby in the 1990s.
Ammonia hydrate and ammonium chloride are likely responsible for the detected spectral features.
The instability of ammonia under strong cosmic radiation highlights the importance of its presence on Europa’s surface.
The discovery of ammonia-containing materials suggests they may have originated from Europa’s subsurface ocean or shallow subsurface during the moon’s geologically recent past, possibly through cryovolcanism or similar processes.
This analysis also hints at significant implications for Europa’s internal structure.
The presence of ammoniated compounds aligns with a subsurface ocean characterized by a thinner, chemically reduced ice shell with a higher pH.
Ammonia’s antifreeze properties are essential, as they lower the freezing point of water ice, allowing for the maintenance of a liquid ocean beneath Europa’s icy shell.
“Faint signals of ammonia have been detected near fractures in the moon’s frozen surface, where liquid water, rich in dissolved ammonia compounds, is expected to ascend,” Emran noted.
“These compounds might have traversed the surface due to recent geologically active cryovolcanic events.”
Ammonia’s presence, which significantly lowers the freezing point of water, acts as a natural antifreeze.
Similar ammonia-bearing species have been identified on other icy objects in the outer solar system, including Pluto, Charon, certain moons of Uranus, and Saturn’s moon Enceladus. However, earlier attempts to confirm ammonia’s presence on Europa produced inconclusive results.
“The identification of ammonia-containing compounds in this research marks the first evidence of nitrogen-based species on Europa, a finding of considerable astrobiological importance due to nitrogen’s fundamental role in life’s molecular structure,” Emran concluded.
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A. Emran. 2026. NH3 detection at Europa’s 2.2 μm absorption band. Planetary Science Journal 6,255; doi: 10.3847/PSJ/ae1291
Source: www.sci.news
