hello, mercury!

I was very excited last week when NASA's MESSENGER probe flew by Mercury on its Herculean journey toward the sun. The mission has already been three and a half years in the making, and it will ultimately land the probe in orbit around the solar system's smallest planet.

For those who aren't up on their planetary exploration history, until last week Mercury remained the only planet in our solar system that we hadn't seen in detail all the way around. We'd seen the surface of small moons hundreds of millions of kilometers further away, but until last week, we'd only seen about half of Mercury's surface—planetary scientists could only guess at what the rest looked like! Luckily for us, the waiting game is largely over. While the mission doesn't officially begin for another three years (this was just the first close flyby), I'd say it can already be called a success with the data that has been sent to mission scientists back in the U.S. The image you see above (full size available here) was one of about 1,200 snapped by MESSENGER on its brief visit. All of these are currently being analyzed by the MESSENGER team, but it looks like they've already noticed some interesting features in the newly observed areas, including geologic features called "rilles" and strange-looking craters.

In case you were wondering why the probe just flew by instead of going directly into Mercury orbit, keep this in mind: The problem with getting a spaceship to Mercury is that anything that goes anywhere near it has to take into account the massive gravitational pull of our star. In order for MESSENGER to get into orbit around Mercury without being sucked into the sun, the spacecraft had/has to follow a dizzying flight plan that slips it into Mercury orbit after making circular orbits that get closer and closer to the sun. Here's a rendering of the trajectory, by the way, and here's a good article that describes the mission. Anyway, congrats to the MESSENGER team, and I'll be looking forward to a successful orbit insertion in 2011! ∞