Missions to Mercury
Mercury has so far been visited by two space probes - Mariner 10 and MESSENGER. A third space craft called BepiColombo is on its way and should enter orbit of Mercury in 2025. Missions to Mercury have observed its many many craters, identifying water in some of them, discovered its weak magnetic field and revealed that although Mercury doesn't have an atmosphere, there are some gases which are detectable around its surface.
Mercury is a tricky planet to get to. Although it's only two planets away from Earth so is fairly close in terms of space distances, it's also very close to the Sun. Sending a space craft directly to Mercury is likely to result in it passing by it too quickly and quite possibly getting absorbed by the Sun. To do it properly requires approaching Mercury at an angle and, if the space craft is to go into orbit of it, finding a way of slowing it down enough so that Mercury can capture it. Any space craft operating so close to the Sun also needs to be able to cope with the intense heat out there. A method used for all missions to Mercury so far is called gravity assist, where a space craft travels to another object and uses the gravity of it to alter its velocity and trajectory (speed and direction).
Mariner 10's visit in 1974 was the first mission to attempt the gravity assist method so became the first space craft to visit more than one destination. It launched from Earth in November 1973 and first went to Venus. As it flew past Venus, it took the first close-up images of it and used the planet to re-route itself to Mercury. Mariner 10 flew past Mercury 3 times, each time sending back lots of juicy information about it. The first flyby was in October 1974, the second in February 1975 and third in March 1975.
MESSENGER launched in 2004 and entered an orbit of Mercury in 2011. It stayed in orbit for just over four years, sending back lots of photos and information before it was sent to crash into the surface of the planet in 2015.
BepiColombo is a space probe that was launched in 2018. It made its first flyby of Mercury in October 2021. It will complete a few more similar manoeuvres to get it to the right speed and position so that it can enter its expected orbit of Mercury in 2025 where it is hoped it'll remain for at least a year.
List of Missions to Mercury
| Name of Mission | Launch Date | Destination | Type |
|---|---|---|---|
| Mariner 10 | 3rd November 1973 | Venus and Mercury | Flyby |
| MESSENGER | 3rd August 2004 | Mercury | Orbiter |
| BepiColombo | 20th October 2018 | Mercury | Orbiter |
