MErcury Surface, Space ENvironment, GEochemistry and Ranging, shortly Messenger, is a NASA probe that will soon do a flyby of Mercury and take approximately 1,200 photographs of the planet’s territory. Mercury is the closest planet to our sun and, after the rejection of Pluto as a planet, the smallest planet in our solar system.

The only other detailed photos of Mercury were taken in 1974 and 1975 by NASA’s Mariner probe. The Mariner only managed to chart 45% of the planet’s territory the rest remaining unknown. Messenger is expected to pass 125 miles above Mercury and after that it should use the planet’s gravity to reposition itself in order to be able to enter Mercury’s orbit in 2011.

NASA scientists hope that Messenger will reveal new facts about Mercury and that it will shed some light on the planet’s unseen territory. Previous exploration led scientists to believe that Mercury’s magnetic field is generated by a large molten-iron core and that the smooth Mercury plains are, in fact, the direct causes of volcanic eruptions. Also, Messenger is expected to bring further information on why Mercury shrunk so much over time.

Mercury is the first space probe to use the solar wind for navigation and it will be the first probe to orbit the closest planet to the sun. The probe didn’t use a single drop of propellant in over six months as it only used the subtle push of sunlight to travel through our solar system. This is very important as propellant will be used in exact maneuvers to position the probe correctly in order for it to achieve the goal of orbiting Mercury.