Massive fault lines that can be seen on Enceladus Moon provide hope that there could be a long-lived ocean that may carry potential alien life. This could be lurking under the icy shell of the moon.
Fault Lines on Enceladus
According to a new study, entitled "Jet activity on Enceladus linked to tidally driven strike-slip motion along tiger stripes," the sliding, adjacent motion along the unique tiger stripes tha coat Enceladus is associated with ice crystal jets that burst from its shell of ice. Such findings could aid in determining the characteristics of the moon and see if it is capable of fostering life.
The strips consist of four parallel fractures of lines in the south pole of the moon. It was first observed by the Cassini spacecraft back in 2005. Cryovolcanism within the area releases ice crystals that are thought to come from the buried ocean of Enceladus from the fractures. This causes a broad material plume to gather on the Saturnian moon's south pole.
Both the plume's brightness and the jets that produce it appear to have variations in a pattern that aligns with a near 33-hour orbit of the moon around Saturn. Because of this, scientists have theorized that jet activity goes up as tidal stress acts upon the fault lines.
However, the theory does not shed light on why Enceladus' jets peak in the hours of brightness after tidal stresses reach their maximum. It also does not explain why a second, smaller peak can be seen shortly after the moon makes its closest approach to Saturn. A novel simulation of the tidal stresses of the moon and the movement of its fractures of tiger stripes identifies a phenomenon that is similar to what can be seen in the San Andreas fault. It corresponds with a jet activity pattern.
Alexander Berne, the team leader of the simulation and a PhD candidate from Caltech, explains that they were able to come up with a sophisticated model that could simulate tide-driven strike-slip movement along the faults of the moon. Such models take into account the role of friction, which triggers the amount of slip of the lines for it to be sensitive to shearing and compressional stresses. The numerical model could simulate the slip along the faults in a way that matched observed variations in the brightness of the plumes as well as variations in space in surface temperature. This suggests that the variations of the jets and plume brightness were managed by a strike-slip movement over the orbit of the moon.
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Tectonics in Space
The researchers discovered that frictional mechanics manage motion within interfaces along the Enceladus' tiger stripes. This is where both fracture sides meet. This also means that during the orbital cycle of the moon, the strips slide and lock periodically. The strike-slip motion ends up lining up with the activity of jets.
The link between jet brightness and strike-slip activity in the simulation allowed the team to hypothesize that jet activity variations are managed by pull-apart presence in the faults. These are bent fracture sections that open beneath strike-slip motion. It allows water to erupt from the subsurface ocean through the shell in order to feed cryovolcanic jets.
Before this study, the researchers did not expect that there would be a high correlation between jet activity and strike-slip motion in models. The study suggests that the Enceladus' tiger stripes open in a different way than what was previously modeled.
Berne explains that such a finding was surprising, as the majority of earlier studies on the subject lead to a broad opening along the fault lines. The researcher also adds that the models suggest that tides play a crucial role in Enceladus and its oceans' evolution across various timescales. He further suggests that the long-term right lateral movement could drive geological feature formation that can be observed around Enceladus' southern pole terrain.
Scientists have previously suggested that the icy moon could be a good target in the search for life beyond Earth across the solar system. The study and model could offer more support to such a notion.
Since the conclusion of the team is grounded on simulations, it requires confirmation through actual observations. Geophysical measurements conducted at the moon through radar would enable the refuting or confirmation of the hypotheses. The researcher aims to keep on investigating ways of using geophysical measurements for the better understanding of conditions that could allow life to form and evolve on this moon.
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