It took NASA's spacecraft, MErcury Surface, Space ENvironment, Geochemistry and Ranging, AKA MESSENGER, six and a half years and some clever maneuvering - But on Thursday March 17th, the unmanned spacecraft made history by successfully entering the 12 hour elliptical orbit of our solar system's innermost planet, Mercury.

While the distance to Mercury is a mere 96.35 million miles, it has been very difficult to get close to it until now. The biggest challenge has been the speed of this tiny planet, which zips around the sun at 106,0000 mph. NASA scientists estimated that in order to get into its orbit, MESSENGER would have to be accelerating at a speed of 65,000 mph - Something that was not possible with our current propulsion system capabilities.

That's when Chen-wan Yen, an engineer at NASA's Jet Propulsion Laboratories came up with the brilliant idea of creating a trajectory or path (see video below) for the Spacecraft that would use the gravity from Earth, Venus and Mercury to provide the propulsion or extra speed required. So essentially every time it flew by one of these planets the gravitational pull from the planet would give it a boost. To gain the final momentum, MESSENGER performed a loop around all three planets and, without using much fuel, managed to successfully accelerate into its final position.

Besides looping around the planets, MESSENGER also had to make 15 loops around the sun, which meant that to get to Mercury, it had to travel a distance of almost 5 billion miles. But as it was flying around, it sent back some amazing pictures and data for scientists to start analyzing.

Now MESSENGER has to face the next challenge - Being closer to the Sun, Mercury's temperature can get as high as 450°Celsius (840°Fahrenheit), most of which is radiated back to space. To combat this, the spacecraft has been covered with a large sunshade, made from ceramic fabric built to withstand high temperatures and also programmed so that the time spent around Mercury's hottest areas is limited to the bare minimum. In addition, the equipment inside the spacecraft has also been built from materials that will be able to withstand the heat.

If everything works according to plan, MESSENGER will remain in the orbit for a year and hopefully send back data that will solve the planet's many mysteries - like why the exosphere is so active and how much of the core of the planet is liquid. In addition, the scientists also hope gain to get better insight into the Earth-like hills and valleys that dot the surface of the planet. Needless to say, they are quite excited at the prospect of getting some intelligence into this planet that is so near, yet has been so unreachable, for all these years.

Resources: Science.NASA.gov