You will be given a definition of a task first, then some input of the task.
Given a scientific passage and an answer, generate a question for the given answer.

Passage: The surface of Mars has volcanoes and canyons. There is a polar ice cap and channels that were once filled with water. Curiosity has found evidence of a flowing stream. Answer: volcanoes and canyons
Output:
What two structures are found on mars?