That Left A Mark...

No, this isn't a photo of the Moon. That mark is the Debussy Crater, and this is a place we haven't photographed at close range before:

Caption: Astronomy Picture of the Day writes: On March 17, the MESSENGER spacecraft became the first to orbit Mercury, the solar system's innermost planet. This is its first processed color image since entering Mercury orbit. Larger, denser, and with almost twice the surface gravity of Earth's moon, Mercury still looks moon-like at first glance. But in this view its terrain shows light blue and brown areas near craters and long bright rays of material streaking the surface. The prominent bright ray crater Debussy at the upper right is 80 kilometers (50 miles) in diameter. Terrain toward the bottom of the historic image extends to Mercury's south pole and includes a region not previously imaged from space.

Image credit: NASA/JHU APL/CIW/Astronomy Picture of the Day

All those inner-solar system, airless planetoids look about the same, don't they?

MESSENGER has been a spectacular engineering and operational triumph already. It has to orbit one of the most inhospitable places on the planet, and as Tony Wikrent pointed out at Corrente a few days ago, it wasn't easy getting there:

Placing spacecraft in orbit may sound rather commonplace today, but getting something into orbit around the first planet is actually quite a feat of space engineering. A spacecraft traveling directly from Earth to Mercury would be accelerated so much by the sun's gravity that it would pass Mercury far too quickly to orbit it.

NASA's solution was to launch the spacecraft in August 2004, and perform a complex series of flybys of Earth (once), Venus (twice), and Mercury itself (three times), which allowed Messenger to be slowed relative to Mercury with minimal fuel, according to Wikipedia. This is one of the reasons I just adore NASA: they repeatedly and spectacularly disprove the wrong-wingers' shibboleth that government is, by nature, unable to get a job done right[.]

New pics from Messenger, first spacecraft placed in ORBIT around Mercury

Now the work of doing what we sent it there to do begins. The MESSENGER website explains what that is:

On March 17, 2011 (March 18, 2011, UTC), MESSENGER became the first spacecraft ever to orbit the planet Mercury. The mission is currently in its commissioning phase, during which spacecraft and instrument performance are verified through a series of specially designed checkout activities. In the course of the one-year primary mission, the spacecraft's seven scientific instruments and radio science investigation will unravel the history and evolution of the Solar System's innermost planet.

First Color Image of Mercury from Orbit

At least, that's part of the mission. But, as with many trips, getting there is half the fun.

Click on the photo too see the full size version of this reduced image. Go to the image credit link, then click on the picture there, to see it at full resolution.