### Saturn's Moon Enceladus
Enceladus, a small icy moon of Saturn, erupts plumes of water vapor and ice particles from fractures in its south polar crust. Two scientists discuss the primary mechanism and location of the thermal energy that powers these geysers.
Scientist 1
The geysers are powered by tidal heating within Enceladus's porous silicate core. As Enceladus orbits Saturn, Saturn's gravitational forces continually deform the moon's core. Water from the global ocean circulates through the porous rock, where frictional heating raises its temperature to over (). This heated water rises as hydrothermal plumes, melting the bottom of the ice shell and escaping through fissures. Therefore, the heat source is deep, global, and drives hydrothermal activity on the ocean floor.
Scientist 2
The heat is generated entirely by tidal flexing and frictional sliding within the icy shell itself, not the core. As Enceladus orbits, gravitational stresses cause the walls of the south polar fractures (tiger stripes) to slide back and forth against each other. This friction melts ice near the surface, forming localized reservoirs of liquid water. Vapors from these shallow reservoirs escape directly into space. Frictional heating is concentrated in the top of the ice crust, and the core remains cold and inactive.
Based on the passage, Scientist 1 and Scientist 2 disagree on which of the following aspects of Enceladus?
- The primary location within the moon where tidal heating generates the thermal energy for the geysersAnswer
- BWhether Saturn's gravitational pull is the underlying source of the energy that deforms the moon
- CWhether water vapor is erupted into space from the south polar fractures
- DWhether the tidal heating occurs in the icy shell, as proposed by Scientist 1, or in the silicate core, as proposed by Scientist 2