Building blocks of amino acids were seen erupting from geysers on Enceladus, orbiting Saturn. What could this finding mean in the search for life in the Solar System?
Orbiting Saturn, the icy moon Enceladus is home to numerous active geysers, which regularly erupt with plumes of water and rocky material. While some of the water released from these vents falls across the surface of that world as snow and ice, a portion soars into space. A new study shows organic compounds, essential to the formation of amino acids, are mixed in with the material erupting from these vents.
Given energy and a favorable climate, these organic compounds could form amino acids. The energy required to form these molecules on Earth is supplied by hydrothermal vents on the ocean floor. Researchers speculate the geysers that feed the vents on Enceladus might provide the energy needed to drive the formation of amino acids on Enceladus.
“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,” said Nozair Khawaja, of the Free University of Berlin.
The materials detected in data from the Cassini spacecraft are composed of nitrogen- and oxygen-bearing compounds, condensed into ice grains. The Cosmic Dust Analyzer, or CDA, which detected ice grains emitted from Enceladus into Saturn’s E ring, collected the data used in this study.
“Saturn’s moon Enceladus is erupting a plume of gas and ice grains from its south pole. Linked directly to the moon’s subsurface global ocean, plume material travels through cracks in the icy crust and is ejected into space. The subsurface ocean is believed to be in contact with the rocky core, with ongoing hydrothermal activity present,” researchers detailed in the Monthly Notices of the Royal Astronomical Society.
In February and March , Cassini flew within 500 kilometers (310 miles) of the surface of Enceladus. By comparison, Voyager 1 never came closer than 90,000 km (nearly 56,000 miles) from the surface of Enceladus during its 1981 flyby.
The Moon, a Ring, how Romantic!
Enceladus is a moderately-sized moon, measuring just 500 km (310 miles) across, about as wide as the state of Arizona.
It is one of the few moons in the Solar System known to have an atmosphere (although it is exceedingly thin). Its mass, 680 times smaller than our own Moon, means Enceladus is unable to hold onto a thick atmosphere, allowing water vapor to escape to space.
This tenuous atmosphere was detected through small changes in the magnetic field of Saturn caused by electrically-charged material surrounding Enceladus.
In 2005, seeing signs of water in the thin atmosphere of that moon provided the first evidence water is continually replenished by geysers on that world.
As the moon rotates (roughly) once every 33 hours, a continuous rain of snow and ice falls, making Enceladus the brightest object in the Solar System. This world is thought to house a vast ocean of salty water beneath its frozen crust.
There, organics are thought to mix with water, before rising up where they freeze into grains of ice hidden in fractures within fractures in the crust of the moon. Rising plumes of water and subsurface material rides up from below, carrying the material to the surface in the form of an eruption, researchers theorize.
Cassini also found that one of the major rings of Saturn — the E ring — is continuously refreshed with new material from the geysers of Enceladus.
“The material shoots out at about 800 miles per hour (400 meters per second) and forms a plume that extends hundreds of miles into space. Some of the material falls back onto Enceladus, and some escapes to form Saturn’s vast E ring,” NASA explains.
This ring, discovered in 1966, is not as defined, or flat, as the other rings of Saturn. This formation resembles a giant doughnut surrounding Saturn.
“Well, heaven forgive him! and forgive us all! Some rise by sin, and some by virtue fall:
Some run from brakes of ice, and answer none: And some condemned for a fault alone.”
― William Shakespeare, Measure for Measure
The Cassini Mission ended in September 2017, as the vehicle was purposely commanded to undertake a death dive into the dense atmosphere of Saturn. This act was undertaken as Cassini faded, preventing the spacecraft from colliding with any of Saturn’s dozens of moon in the future.
In Greek mythology, Enceladus was a giant who fought a legendary battle against Athena during the Gigantomachy, a mythical war between the gods and giants. This story provided a popular theme for vases, plates, and works of art.
Out in the solar system, several worlds are potential homes for simple life, like that which dominated our own world for the majority of its history. This new finding, combined with the possibility of a layer of complex organic materials at the surface of ocean of Enceladus, makes this world a promising target in the quest for extraterrestrial life.
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