Name all the planets in our solar system without a moon.

While many planets in our solar system boast a collection of natural satellites, from Earth's single familiar orb to Jupiter's numerous accompanying worlds, there are two notable exceptions. These are the innermost planets, Mercury and Venus, which journey around the Sun without any moons in tow. This characteristic makes them unique among their planetary siblings and offers interesting insights into the gravitational dynamics of our cosmic neighborhood.

Mercury, being both the smallest planet and the closest to the Sun, faces significant challenges in retaining a moon. Its modest mass means it has a weaker gravitational pull, making it difficult to capture and hold onto any celestial body in orbit. Furthermore, the Sun's immense gravitational influence in this region creates an unstable environment. Any potential moon around Mercury would likely find its orbit disrupted, either being pulled away by the Sun or spiraling into the planet itself due to the strong tidal forces. The stable orbital zone, known as the Hill sphere, for Mercury is simply too small and too close to the Sun's dominant pull for a moon to persist over long periods.

Venus, despite being much closer in size and mass to Earth, also travels moonless. Its proximity to the Sun plays a similar role to Mercury's, with the Sun's strong gravity making it challenging for Venus to maintain a stable moon. Scientists theorize that Venus may have once had a moon, possibly formed from a giant impact much like Earth's Moon. However, models suggest a complex history involving a second impact and Venus's peculiar retrograde (backward) rotation, which could have altered tidal interactions, causing any moon to spiral inward and ultimately crash into the planet.

The absence of moons around Mercury and Venus highlights the delicate balance of gravitational forces at play in a planetary system. While other planets like Mars have two small moons, and the gas giants host dozens, the intense solar gravity and unique formation histories of Mercury and Venus have left them as solitary travelers in their orbits. Their moonless state provides a natural laboratory for understanding the limits of satellite formation and stability within the inner solar system.