NASA joins next Mercury mission

After decades of relative obscurity, the closest planet to the Sun is emerging from the scientific shadows.  Following up on the successful MESSENGER mission, NASA has recently announced that it will send an instrument to Mercury as part of the BepiColombo mission.   The joint European-Japanese mission, due to launch in 2015, will send two additional orbiters to the first planet.  NASA's contribution will be the Strofio instrument, which will study the gaseous environment around the planet.

Mercury is a tough destination to explore.  When facing the Sun, the surface can heat to over 425 degrees Celsius .  The shadowed polar regions, on the other hand, can dip as low as -190.  These dramatic shifts in temperature place enormous stress on the spacecraft sent to study the planet.  Just getting there in the first place, however, can be even more challenging.  When we send a spacecraft to Mars or Jupiter or Saturn, we can send it on a direct path.  When the probe arrives, it skips along the planet's atmosphere to generate friction and slow down.  

The BepiColombo mission will send a pair of orbiters to Mercury.  (Image credit: Max Planck Institute for Solar System Research)

The problem is, Mercury doesn't have a meaningful atmosphere, so this technique doesn't work.  Instead, the orbiter must take a winding path through the solar system  designed to put it in the perfect place, at the perfect time, with the perfect velocity.  Only then will the spacecraft be able to enter orbit.  BepiColombo, for example, will spend more then six years slingshotting around Earth once, Venus twice, and Mercury four times before it can even begin its one-year mission.

Because of these difficulties, it wasn't until MESSENGER arrived in mid-2011 that we even had complete surface imagery of the planet.   Now, we've discovered the planet has an anomalous magnetic field, a unique surface composition, and traces of polar ice. BepiColombo will follow up on these discoveries.

Why the funny name?  Guiseppe "Bepi" Colombo was a twentieth-century Italian astronomer and engineer.  He first developed the slingshot techniques that expedite outer-planets missions and enable the study of Mercury.