What is a primary engineering concern for any lander planned for Io, distinct from concerns for Europa missions?

Answer

Surviving the volcanic fallout.

For missions targeting Io, the concern is surviving the volcanic fallout, intense heat, and corrosive sulfur compounds, whereas missions targeting Europa focus on penetrating the ice shell.

What is a primary engineering concern for any lander planned for Io, distinct from concerns for Europa missions?
Jupiterplanetsolar systemmoonsIo