Lichens Call This Space Rock Home

Dr. Svend Buhl and a new meteorite find.

Like you, I’m a member of various online discussion groups. One of my favorites is the Meteorite-list, a group of individuals more than 950 strong strung across the planet, who are fascinated by space rocks. The “metlist” includes scientists as well as hobbyists and is THE place to get a question answered about meteorites. While the discussion can be rancorous and even political at times, everyone tries to play nice. Check it out.

Earlier this week, Dr. Svend Buhl of Germany posted a photo on the metlist of a curious meteorite he and his companions found last year in the territory of Western Sahara that borders Morocco. The hunters, which included Marc Jost and Pjotr Muromov, spent days criss-crossing vast stony plains by automobile in 117 degree temperatures looking for rocks covered in black fusion crust, a telltale sign of a meteorite. Hundreds of times they stopped and examined suspect rocks only to be fooled by terrestrial look-alikes.

130 gram G'idat Amwizirat 001 meteorite (field name given by the team). Lichens were growing on this and another fragment of the same meteorite found nearby. The cube measures 10mm or a little less than 1/2" across. Credit and copyright: Dr. Svend Buhl

Six days into their so-far fruitless search, as Svend and Marc were debating where to camp that night, Pjotr interrupted them with the words every hunter wants to hear: “”I think I’ve found something very interesting.” Svend leaped from his seat, followed Pjotr back along the car’s tire tracks and stopped dead in front of a pristine meteorite with black crust and fresh gray interior. Not only was the 4.6 ounce (130 grams) fragment a rare type of space rock that originated from a lava flow on an asteroid, but the alien rock hosted an earthly guest in the form of a lichen.

A Hammered Shield lichen, a common foliose (leafy) variety, on the rock wall along Duluth's Amity Creek. Photo: Bob King

Lichens are one of the most successful life forms on the planet because they’ve learned the strategy of cooperation. They’re really two or even three creatures in one: a fungus and a green alga are most common, but fungi and photosynthesizing bacteria can also pair up. The algae use sunlight through photosynthesis to create sugars that feed both it and the fungus, while the fungus protects the alga and provides a surface for the plant to soak up needed water and essential minerals gleaned from dust or the rock to which it’s attached. Lichens come in three basic varieties: foliose (leafy), crustose (crusty) and fruticose (shrubby) and thrive well in a range of climates from cold and wet to hot and dry. Dr. Buhl’s find was a fruticose lichen that chose extraterrestrial rocks as the perfect places to put down stakes. Even though the meteorites looked as if they’d fallen yesterday, they likely hit Earth several if not dozens of years ago. How do we know? Most lichens grow v-e-r-y slowly.

A crustose lichen found growing on a meteorite of my own found several years ago in the Sahara Desert. Photo: Bob King

Over time, cycles of freezing and thawing, coupled with weak acids brought to the rock surface by lichens, can loosen mineral grains, slowly converting the stone to soil. If it hadn’t been found by Buhl’s team, part if not all of the meteorite would have eventually become one with the desert sands. Through the action of the lichen and weathering, extraterrestrial matter loses its individual identity and merges with that of the Earth.

The hunters' nightly camp in the Saquia al Hamra desert in Western Sahara. Credit and copyright: Dr. Svend Buhl

How many meteorites from the long corridor of time stretching into our planet’s deep past are now part of the soil in our gardens? It’s also interesting to consider that Buhl’s lichen may be using minerals in the meteorite – mostly similar to the earthly minerals plagioclase, pyroxene and olivine – to supply essential substances to both algae and fungi. How wonderful it is to witness the extraordinary conversion of rocks from the asteroid belt into earthly life and soil courtesy of the ever-cooperative lichen, happy to call anywhere home.

For more on Dr. Buhl and his team’s meteorite hunting adventures, I highly recommend you stop by his website and read the whole story. The photos alone will warm you up at this coldest time of year.