Paleontologists often have to brave extreme environments, like the Gobi Desert or the mountains of Antarctica, to track down new fossils. But a study released yesterday in The Philosophical Transactions of the Royal Society suggests looking to an even more remote environment for fossil hunters: the Moon.
The open access study was led by University of Kent space scientist Mark Burchell, who notes in the paper that "the idea that biological material can successfully migrate through space is an old one."
Indeed, the concept of "panspermia," or the distribution of lifeforms throughout the universe via asteroid, meteor, and comet impacts, was pioneered by the Victorian scientist Svante Arrhenius.
But debate over the hypothesis has heated up over the last few decades, especially when, in 1996, astrobiologists suggested the Martian meteorite ALH84001 might contain fossilized Martian microbes.
Surprisingly, Burchell's team says it's the first to actually test the legitimacy of the idea that fossils dislodged from Earth could survive the original impact, then a trip through space, and finally, another traumatic collision with the lunar surface.
Naturally, the experiment involved a cool projectile-launcher called the Light Gas Gun (LGG). Designed specifically to test hypervelocity impacts in space, the LGG can shoot small projectiles at speeds of up to 7.5 kilometers/second into a container of water, where the debris can be examined.
In their experiment, Burchell and his colleagues cemented fossilized ancient diatoms (a major algae group) into a projectile containing diatomaceous earth (soft sedimentary rock) and water. They then froze the mixture to simulate the environment meteoroids would encounter.
"[Diatoms] are used on Earth to study the history of sites and monitor changes, so they are a natural thing to look at," Burchell told me over email. "They are also conveniently small and easy to source. For a first study to see if something is plausible, convenience is good."
The team shot their mock meteoroids into the water target at speeds ranging between 0.4 and 5 kilometers/second. As expected, the higher speeds resulted in increased fragmentation of the samples. Even so, all nine shots that the team conducted resulted in samples that were still recognizably biological. In fact, the meteoroid fired at the top speed of 5.34 kilometers/second retained four intact diatom fossils.
Burchell's team showed that fossils kicked up by impacts on Earth can indeed end up in surprisingly good condition on the Moon.
"The Moon is a good place to look," Burchell told me. "[It] has no atmosphere, little surface volcanoes or plate tectonics, and so preserves material better than the very active Earth." But he also noted that "continual impacts on the surface do break up rocks with time, so it is not perfect."
Regardless, it's exciting to imagine prospecting for lunar fossils, which may be preserved in a completely different manner to their counterparts on Earth. I guess it's time to start investing in a promising new career option: astropaleontology.