The two planets having no natural satellites are:

Concept

A natural satellite is a celestial body that revolves around a planet under gravity. To identify planets without satellites, compare the known natural-satellite count of each planet and look for a pair whose count is zero for both.

Application

Mercury has no natural satellite, and Venus also has no natural satellite. Thus both members of the pair satisfy the required condition.

Contrast

• Saturn has a large system of natural satellites, so any pair containing Saturn fails the condition.

• Earth has the Moon, while Jupiter has many natural satellites; therefore neither has a zero satellite count.

• Mars has two natural satellites, Phobos and Deimos, so a pair containing Mars fails the condition.

Result

Therefore, the two planets having no natural satellites are Mercury and Venus.