Europa’s Subsurface Ocean
Jupiter’s moon Europa is covered by a thick ice shell, beneath which a liquid water ocean is believed to exist. Two models propose different mechanisms for how this liquid ocean is maintained.
*Model 1*
Liquid water is maintained primarily by tidal heating. As Europa orbits Jupiter in an eccentric path, the gravitational pull of Jupiter and neighboring moons fluctuates. This variation causes continuous tidal flexing, which generates friction-induced heat within Europa's mantle and ice shell. This heat melts the base of the ice shell, keeping the subsurface ocean liquid. Model 1 assumes that Europa's rocky core contains negligible radioactive elements, meaning radiogenic decay contributes almost no heat to the ocean.
*Model 2*
Liquid water is maintained primarily by hydrothermal activity driven by radiogenic decay in Europa's rocky core. Over billions of years, the decay of radioactive isotopes (such as uranium-235 and potassium-40) in the core has released steady thermal energy. This heat escapes into the bottom of the ocean through hydrothermal vents, keeping the water liquid. Model 2 assumes that Europa's orbit is highly stable and circular, resulting in negligible tidal forces and flexing, and thus tidal heating is insufficient to prevent the ocean from freezing.
Based on the descriptions of the two models, which of the following statements best identifies a primary belief of Model 2 regarding the heat source of Europa's subsurface ocean?
- AFriction-induced heat from gravitational tidal flexing is the dominant source keeping the ocean liquid.
- BSolar radiation warming the surface of the ice shell is the primary driver of subsurface melting.
- Heat from radioactive decay in the rocky core is the primary source of warmth keeping the ocean liquid.Cevap
- DConductive heating from a molten metallic iron core is the sole contributor of heat to the ocean.