A unique meteorite that fell on a Soviet military base in Yemen in 1980 may have come from one of the moons of Mars. Several meteorites from the Red Planet have been found on Earth, but this could be the only piece of Martian moon rock.

Andrei Ivanov, who is based at the Vernadsky Institute of Geochemistry and Analytical Chemistry in Moscow, Russia, spent two decades puzzling over the fist-sized Kaidun meteorite before he decided that it must be a chip off Phobos, the larger of the two Martian moons. "I can’t find a better candidate," Ivanov told New Scientist. The research is published in the March 2004 issue of Solar System Research and is entitled, "Is the Kaidun Meteorite a Sample from Phobos?"

Mars has two natural satellites, or moons, called Phobos ( Greek for "Fear") and Deimos ("Terror"). Phobos is one of the darkest objects in our solar system, a mostly colorless (dark gray) satellite, except for a faint reddish-orange hue cast by reflection of sunlight off Mars. Because of its visual darkness, a full moon on Mars would do little to brighten the night.

The Kaidun meteorite is like no other in the world- and 23,000 of them have been catalogued. It is made of many small chunks of material, including minerals never seen before.

Working with Michael Zolensky of the NASA Johnson Space Center in Houston, Texas, Ivanov used an electron microscope to look at the space rock’s crystal structure, peered through its minerals using X-rays and vaporised fragments to catalogue the elements inside. And every sample turned out to be something "new and weird", says Zolensky.

Among the odd materials in the meteorite were two fragments of volcanic rock- which only forms in massive, planet-like bodies with a core, mantle and crust.

The meteorite "holds a special place in the world’s meteorite collection," wrote Ivanov. "Kaidun is characterized by an unprecedentedly wide variety of meteorite material in its makeup….nearly 60 minerals and mineral phases have been identified in Kaidun, including several never found in nature, such florenskiite, FeTiP, the first known phosphide of a lithophilic element [made from phosphorus, titantium and iron]. .Kaidun is the only known example of highly shocked carbonaceous chondrite (a carbon-rich meteorite material]."

But much of the meteorite is a kind of carbon-rich material that only occurs in asteroids. Zolensky thinks this paradox could be resolved if the meteorite comes from a Martian moon. Both Phobos and Deimos are thought to be asteroids captured by Mars as they wandered through space. That would explain the carbonaceous material. And the pieces of volcanic rock could be bits of Mars, thrown into orbit when other asteroids crashed into the planet.

Phobos is the more likely candidate: it orbits only 6000 kilometers from the planet’s surface, much closer than Deimos, and so has probably mopped up a lot more fragments of Mars rock.

Ivanov described the finding in his research abstract, "The Kaidun meteorite exhibits an incredible diversity of extraterrestrial material. The parent body of the meteorite is mainly composed of carbonaceous chondrite material of the second petrological type. The meteorite is specific in its composition: it contains numerous fragments and inclusions formed at an early stage of the Solar System evolution by nebular condensation, gaseous metasomatosis, agglomeration, and other processes, and two different fragments of alkaline-enriched differentiated material, which entered the parent body as a result of different events. The data on the lithologic composition of the Kaidun meteorite give strong arguments for considering the meteorite’s parent body to be a carbonaceous chondrite satellite of a large differentiated planet. Phobos, the moon of Mars, is the most probable candidate. Many features of the Kaidun meteorite can be well explained within the framework of the popular hypothesis of Phobos’ origin based on the nebular capture model."

The idea is plausible, if somewhat speculative, says Sara Russell, a meteorite expert at the Natural History Museum in London. "There have been no landers sent to Phobos and so almost nothing is known about the composition and geology of this body." Zolensky thinks that an unusual asteroid could have been the source. Hope of resolving the mystery rests with the European Space Agency, which has been asked by UK scientists to consider sending a mission to Phobos as part of its Mars exploration program.

Related Web Pages

Mars Rovers: JPL

Ivanov: Alkaline rich Kaidun meteorite

Mars Meteorite Home

Kaidun Meteor Image