I believe it was part of the Mariner series of satellites
Mercury and Venus have no natural satellites.
Mercury, Venus and Mars have no satellites.
Since Earth's Moon was likely formed from a chance collision, the formation of moons may not have been a stable process in the inner solar system. Any moons that formed around Venus or Mercury could have been swept away by the stronger gravity of the Sun, as might smaller moons around Earth. If Mercury or Venus ever had satellites, they were lost long ago.
Mercury and Venus are the two planets in our solar system that do not have any natural satellites or moons.
Venus is one of the few planets that doesn't have any satellites orbiting around it. Venus also is a planet with no moons.
No natural satellites of the planets Mercury or Venus have ever been discovered.
Mercury and Venus have no known natural satellites (moons).
Mercury and Venus.
Both Mercury and Venus have no moons.
Mercury Venus
Mercury and Venus don't.
Mercury and Venus have no natural satellites.
Mercury and Venus have no known natural satellites (moons).
All of the planets do except for mercury and Venus.
Mercury and Venus.
Mercury, Venus and Mars have no satellites.
Mercury and Venus do not have any natural satellites or moons. They are the only two planets in our solar system that do not have any known moons orbiting around them.