What orbits the Sun between Earth and Mercury?
Transit of Mercury Transit of Mercury A transit of Mercury across the Sun takes place when the planet Mercury passes directly between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Mercury appears as a tiny black dot moving across the disk of the Sun. Transits of Mercury with respect to Earth are much more frequent than transits of Venus, with about 13 or 14 per century, in part because Mercury is closer to the Sun and orbits it more rapidly. Transits of Mercury occur in May or November. The
Mercury (planet) significant technical challenges, because it orbits so much closer to the Sun than Earth. A Mercury-bound spacecraft launched from Earth must travel over into the Sun's gravitational potential well. Mercury has an orbital speed of , whereas Earth's orbital speed is . Therefore, the spacecraft must make a large change in velocity (delta-v) to enter a Hohmann transfer orbit that passes near Mercury, as compared to the delta-v required for other planetary missions. The potential energy liberated by moving down the Sun's potential well becomes kinetic energy; requiring another large delta-v change to do anything other than rapidly pass by