What Is The Most Plausible Mechanism By Which The Sputnik Planum Ice Plain On Pluto Could Have Undergone Rapid Viscous Relaxation To Achieve Its Remarkably Flat And Smooth Surface, Given The Presence Of Tholins In The Surface Ices, And How Might This Process Inform Our Understanding Of The Timescales For Cryovolcanic Resurfacing On Other Kuiper Belt Objects?
The most plausible mechanism for the rapid viscous relaxation of Sputnik Planum on Pluto, resulting in its flat and smooth surface, involves the role of tholins in reducing the viscosity of nitrogen ice. Here's a structured explanation:
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Role of Tholins: Tholins, dark organic compounds formed from UV radiation interacting with simple organic molecules, are mixed into the nitrogen ice. They likely act as impurities that lower the ice's viscosity, possibly by reducing the melting point or altering the ice's grain structure, making it more susceptible to flow.
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Viscous Flow Mechanism: At Pluto's low temperatures (around 38 K), nitrogen ice is normally hard. However, the presence of tholins may facilitate viscous flow by lowering the ice's viscosity. This allows the ice to deform more easily under stress, such as pressure from overlying layers or tectonic activity.
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Cryovolcanic Resurfacing: Cryovolcanism could play a role by bringing warmer materials to the surface, temporarily increasing temperatures and further reducing ice viscosity. This process might contribute to rapid surface relaxation and resurfacing.
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Timescales and Implications: The rapid viscous relaxation observed on Pluto suggests that similar processes on other Kuiper Belt Objects (KBOs) could occur on shorter timescales than previously thought. This implies that many KBOs might have younger, geologically active surfaces, challenging assumptions about their inertness and indicating a more dynamic history.
In conclusion, tholins facilitate rapid viscous relaxation by lowering the viscosity of nitrogen ice, enabling Sputnik Planum's smooth surface. This mechanism suggests that other KBOs with similar compositions may experience rapid resurfacing, highlighting their potential for recent geological activity.