Which of the following is NOT a criterion of a planet?

To understand why "must support life" is not a criterion for classifying a celestial body as a planet, it's essential to recognize the official definition of a planet as outlined by the International Astronomical Union (IAU). According to the IAU, a planet must meet specific criteria: it must orbit the sun, be spherical in shape (maintaining a hydrostatic equilibrium), and have cleared its orbit of other debris (meaning it must be gravitationally dominant in its neighborhood).

Unlike the other criteria that focus on the physical and orbital characteristics of the celestial body, the requirement of supporting life is not necessary for a body to be classified as a planet. Many planets, including our own, do not have conditions suitable for life, yet they still meet the definitions set forth by the IAU. Therefore, the notion of a planet needing to support life is irrelevant to its classification as such. This distinction is crucial for understanding the characteristics that define a planet versus those that define potential life-supporting environments.