Some of you may have read my profile and know I collect meteorites. I have been doing so for over a decade but my interest in rocks from space goes back to 1968 when I first saw Meteor Crater in Arizona and walked down what is now Astronaut Trail.
I have studied meteorites and impacts extensively, especially our very own Chesapeake Bay Impact Crater, 6th largest in the world and 58 miles in diameter located at Cape Charles, VA. We have over 53,000 classified meteorites in the world and dozens from the Moon and Mars, and Vesta.
We were able to classify the Moon and Mars meteorites after we landed on the Moon with the Apollo missions and then on Mars with Viking 1 and 2 back in 1976. We confirmed rocks from Vesta due to detailed spectroscopic observations of the second largest asteroid in the solar system and Dawn is helping to pinpoint possible craters that could be the origin point.
It is interesting to note that we had the lunar and martian samples in our possession for some time before we could classify their origin. Meteorites must undergo scientific examination and classification in order to be classified as a meteorite. The lunar and martian meteorites, as well as those of Vesta, had unique characteristics - different from other meteorites. We couldn't classify them, although it was suspected where they came from, until we had the scientific data from actual samples and observations.
With MESSENGER in orbit around Mercury and gathering great quantities of data, the question has arisen as to "where are the meteorites from Mercury"? It is thought that somewhere on Earth we should have samples from the planet closest to the Sun but so far their discovery has eluded us. I personally am aware of one meteorite called NWA 011 that for a time was thought to be a potential Mercurian meteorite but that still remains to be seen.
There is a great article about this intriguing question in Sky & Telescope online: http://www.skyandtelescope.com/community/skyblog/newsblog/Wanted-Meteorites-from-Mercury-136803313.html
Sky Guy in VA