Exploration of Mercury - Interest in Mercury

Interest in Mercury

Mercury has not been a primary focus of many space programs. Since the planet is so close to the Sun and spins on its own axis very slowly, its surface temperature varies from 427 °C (801 °F) to -173 °C (-279 °F). There is discussion of the possibility of terraforming Mercury and inhabiting the poles of the planet, but this possibility lies far in the future, being significantly less practical than terraforming Mars or even Venus. The current interest in Mercury is derived from the unexpected observations of Mariner 10. Before Mariner 10, it was thought that the planet simply revolved around the sun in a highly elliptical orbit. The planet had been observed through ground-based telescopes, and scientists felt that they were able to draw a great many inferences from such observations. Mariner 10 provided data that contradicted many of these.

Another reason why so few missions have targeted Mercury is that it is very difficult to obtain a satellite orbit around the planet on account of its proximity to the Sun, which causes the Sun’s gravitational field to pull on any satellite that would be set into Mercury's orbit. Furthermore, spacecraft naturally accelerate as they approach the greater gravitational pull of the Sun, but must slow down in order to orbit Mercury, so this entails considerable fuel requirements. This is different with planets beyond Earth’s orbit where the satellite works against the pull of the Sun. Therefore it requires a great amount of energy to reach and observe the planet. Mercury's lack of an atmosphere poses further challenges because a probe attempting to land on Mercury would not be able to aerobrake or use a parachute type device. Thus a landing mission would have rather demanding fuel requirements.