Which of Mars' moons is larger?

Phobos is the larger moon of Mars, which is why it is the correct answer. With a diameter of about 22.4 kilometers, Phobos is significantly larger than Deimos, which has a diameter of around 12.4 kilometers. The size difference between the two moons is notable, as Phobos is more than 80% larger in diameter than Deimos.

Phobos also has a unique orbit that brings it closer to Mars than Deimos, making it not only larger but also more prominent in the Martian sky as it appears to move quickly across the sky, completing an orbit in about 7.5 hours.

Understanding the relative sizes of Mars' moons helps highlight not only their physical characteristics but also their gravitational influences, and how they interact with Martian geology and atmosphere. The significant size difference is a key factor in studying the moons of Mars in the context of their potential for future exploration or understanding their formation.