Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Uranus is the least massive outer planet. Its mass is only about 14 times the mass of Earth. Like all of the outer planets, Uranus is much less dense than Earth. Gravity is actually weaker than on Earth's surface. If you were at the top of the clouds on Uranus, you would weigh about 10 percent less than what you weigh on Earth. Answer: uranus
A:
Which is the least massive outer planet?