A few weeks ago, NASA’s Mercury MESSENGER space probe crash landed on the surface of the planet. This was not a mistake, scientists had deliberately sent it hurtling towards the surface of mysterious Mercury. It brought to an end a highly successful mission to learn more about the smallest planet in the inner solar system.
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) was launched by NASA in August of 2004 and arrived at Mercury in April 2011. You might be wondering why it took so long to get to Mercury, which is much closer to us than e.g. Jupiter. The reason is that the space probe could not fly directly to Mercury, otherwise it would have just whizzed straight past. Instead it had to go on a circuitous route so that when it arrived at Mercury it was moving slowly enough to be able to go into orbit about the planet. During this flight it flew past Earth once and past Venus twice. These fly-bys, as well as being used to slow down a space probe (in this case, usually they are used to speed them up), are also used to test the instruments.
During the four years that MESSENGER has been orbiting Mercury it has obtained a wealth of data. It would take me too long to describe all of its findings, but some highlights are
Mercury has a magnetic field
Discovery of water in craters
Discovery of volcanism
Discovery of organic compounds
Discovery of unusually high concentrations of calcium and magnesium
As is often the case with gathering more information than we have ever previously gathered, we now have more questions about Mercury than we have answers. How can such a slowly rotating planet (it rotates once every 58.6 Earth days) produce a magnetic field? Scientists are now going to have to wait a while to find out more about Mercury, the European Space Agency (ESA) plan to launch BepiColombo in January 2017, it will arrive at Mercury in January 2024.