All this week, SPACE.com looks at the latest news from the world of meteorite hunters and profiles many of the key players in the meteorite market. Find out what drives them and how they came to dedicate their energy to rocks from space.

Five years ago, Marvin Killgore hung up his contractor's license to pursue meteorite collecting and dealing full time. This journeyman plumber-turned-meteorite collector wanted to his hobby to become his profession, and dedicate himself to studies that would advance the understanding of the solar system.

While most meteorite enthusiasts are strongly interested in the science of the rocks they collect, Killgore's passion begins where others' ends. He collects and trades meteorites so that he can study them. Not satisfied with simply supplying scientists with meteorites and then waiting to hear what they learn, Killgore has collaborated with a handful of scientists to do his own research on fallen spacerocks.

Several years ago he became interested in studying impact craters on Earth and how meteorite fragments are strewn around an impact site. One scientific controversy particularly interested Killgore, and drew him to the research of Arizona State University geologist John McCone.

Several iron meteorites that Killgore collected had tiny circular impressions on their surfaces, often not much wider across than large grains of sand. They appeared to be tiny craters on meteorites.

The prevailing explanation for these features is that they are caused by bubbling that results when the surface of the meteorite heats up and melts while jetting into Earth's atmosphere.

But McCone thought differently, and so did Killgore: They believed the circular impressions were actually craters caused by the impacts from tiny micrometeorites out in space. McKone had reached the same conclusion, so the two teamed up to investigate.

"We decided we would work on what caused those impressions, and what size and velocity of a particle it would take to make a crater in an iron meteorite in flight. It was kind of a fun thing," Killgore recalls.

The dimple in the bottom of this fragment of the Sikhote-Alin meteorite may have been caused by the impact of a micrometeorite in space, Killgore says.

They needed a number of samples to study, so Killgore headed to far-eastern Siberia to hunt for meteorites at the fall-site of the famous Sikhote-Alin meteorites.

A giant iron meteorite, estimated to weigh some 70 tons, streamed across the sky above northeastern Siberia in February, 1947 and exploded about 3 miles above the ground. It scattered a wide region of wilderness with fragments of extraterrestrial metal, devastating portions of the forest and smashing more than 100 craters that ranged from several feet to almost 90 feet across.

Killgore found a number of iron meteorites with small "craters" in the surface, and McCone was able to argue convincingly that the origin of these was indeed micrometeorite impacts in space.

Another scientific project Killgore is involved in concerns a material called Libyan desert glass -- lumps of yellow glass that have been found in the Sahara desert. Scientists believe that this glass is forged by the shock wave of very energetic meteorite falls.

Some meteorites annihilate themselves in massive explosions close to the ground, causing flashes of heat that are hot enough to melt the sand into pure glass. Fragments of minerals that may be the remnants of meteorites are trapped within the glass. So are small bubbles that could hide secrets about the meteorites that produced them. Killgore is working with scientists to analyze the composition of these "inclusions" using a specialized laser.

Killgore's dedication to science is respected in the scientific community. The Meteorite Nomenclature Committee, which assigns names to, and catalogs all known meteorites, has taken the notable step of giving Killgore permission to classify his own meteorites.

Before a meteorite can be named, it must be thoroughly examined and tested. This is usually done with a device called an electron microprobe, which uses a precision electron beam to analyze the chemical composition of minerals in the rock. Scientists use this analysis to determine what type of meteorite they have found so it can be named and classified according to its type.

This slice of the Portales Valley meteorite from Killgore's collection shows rocky patches separated by shiny metal. The slice measures about 12 inches across.

Jeff Grossman is a geologist at the U.S. Geological Survey and the editor of the Meteoritical Bulletin, the annual publication that catalogs new meteorites.

"Marvin Killgore is the only meteorite dealer that I know about who has gained access to an electron microprobe and learned how to use it," Grossman wrote in an e-mail correspondence to SPACE.com. "Given this, his knowledge of meteorites and his relatively close working relationships with several meteoriticists (e.g., Alan Rubin at UCLA), we see no reason why he cannot classify meteorites."

The only stipulation was that Killgore's first few classifications should be verified by an established expert. The first meteorite that Killgore found -- after he had been given tentative approval to classify his own meteorites -- was a rare type that was very challenging to classify because there were very few specimens like it. Killgore determined that it was an R-chondrite, a classification that was verified by recognized experts.

A conversation with Killgore often leads to discussions on Ramon spectroscopy and rare minerals with names such as crystobolite, pyroxene, and feolite, and their relative abundance within various meteorites. Killgore's depth of knowledge and familiarity with geochemistry makes it surprising to learn that he left high school before completing 11th grade.

Killgore grew up plumbing houses, and by the time he was a teenager he was itching to get out of school and work full time in his family's construction business.

In the mid-1970s, Killgore moved to New Mexico from Arizona to work in the mines. There he became interested in geology. During his shift, he was digging and blasting, but in his off time he studied geology books and became something of an expert. Soon he was teaching others.

"They used to send geology students from the New Mexico School of Mines down so I could show them what a breccia zone was," Killgore recalls. (Breccia are sharp, fragmented rocks embedded in a layer of small-grained material like sand or clay. "So I taught a lot of geologists how to be geologists."

Killgore moved back to Arizona and earned his plumber's license in 1980, the same year his son was born. He worked happily as a contractor until the early 1990s, when meteorites really became his passion. He first learned about meteorites from somebody who used to buy gold from him. Between plumbing jobs Killgore would often prospect for gold, sometimes finding enough to pay a few bills. 

This photo of a slice of the Imilac meteorite from Killgore's collection shows an area about 5 inches across. Colorful glassy crystals are held in a metal matrix.

After one successful trip, a gold buyer told Killgore he should try his hand at meteorites, and gave Killgore a sample so that he would know what to look for. Because of their high metal content, meteorites -- like gold -- can be found with a metal detector. Killgore took his equipment out to the desert and began looking closer at all the rocks he previously tossed aside.

"I went out and started looking for meteorites and I started finding them," Killgore said. He took that as a sign to continue. "Some people hunt all their lives and never find a meteorite. Well, I found one within the first week of hunting. And then I got the bug from then on."

When he first started, Killgore knew absolutely nothing about meteorites. "I was one of these guys who came in with the 'carborashus chawndite.' " Killgore said, mimicking his early lack of familiarity with meteorites. The real term is carbonaceous chondrite. It is a primitive type of stony meteorite that contains organic compounds and minerals that have been influenced by the presence of water and oxygen. They are probably the plainest-looking meteorites, but they are among the most interesting because of their possible link to the origins of life.

He kept searching, hunting, and learning and before long he quit plumbing altogether to devote himself entirely to meteorites.

"It's a fun business, interesting," Killgore said. "I'm either on the airplane, or I'm out hunting, or I'm out buying, or I'm out trading one thing or another. It's a kind of freedom. It keeps me in a field that's interesting, doing research. It's kind of nice to be able to find something new and to be able to report it in a scientific journal."

Killgore said he doesn't regret not attending college -- he did get his high school diploma years later and he is pleased with the direction of his life -- but he now thinks education is tremendously important.

"I'm not saying that an education is going to make or break you," Killgore said. "If you're a kid and you're out there, you should get an education first. And then if you don't want to use it, that's fine."

Killgore will continue with his meteorite dealing, but his dream now is for some museum to buy his collection and allow him be curator so that he can devote himself full time to study.