NASA's Messenger (MErcury Surface, Space ENvironment, GEochemistry and Ranging) probe made its first fly-by of Mercury today and over the next few months will settle into orbit for an extended study of the planet.

Messenger is the first probe to visit Mercury since Mariner 10 back in 1975.

Because of its position in the solar system, Mercury is very unique planet. Constantly seared by heat and radiation from the sun, the chemistry of Mercury has been skewed. All of the volitile elements like oxygen, hydrogen have been cooked away. The ordinary compounds like silicates and oxides can't form causing a very different high energy chemistry.

All that is left of Mercury over the eons is a cinder of heavy elements and minerals formed at very high temperatures.

Of all the planets, Mercury is 2nd in density only to the earth. It has no atmosphere but alpha particles (helium nuclei) are easily detected. This is a marker of radioactive decay from heavy elements like uranium or thorium or radioactive isotopes of less exotic elements.

If we could ever figure out how to mine Mercury, it would probably be a mineralogical treasure house.

Mercury is heavily cratered and sports a giant crater that covers almost 1/3 of the planet and nearly blew the planet apart.

In the days to come we should see some cool photos of the roasted planet.