Earth is an unforgiving place. Volcanoes erupt, rivers erode, continents break up — it's a small miracle every time a millions-of-years-old creature is found fossilised in rock. By comparison, the moon is dead and lifeless; astronaut footprints will be preserved forever in moon dust. So it's the moon that could hold the secrets to life on ancient Earth.
In a new study, Mark Burchell at the University of Kent, UK, looks at whether fossils from Earth could be found on the moon intact. Pieces of Mars and the moon launched by ancient space impacts have been found on Earth — perhaps the opposite would be true as well? The bigger question, though, is whether fossils launched from Earth could even survive smashing into the moon. To that the end, the scientists needed a fake meteoroid and a gas-powered gun. Jacob Aron describes the wonderful process for New Scientist:
The team powdered rock containing [fossils of diatoms, a type of algae] then mixed it with water and froze it to replicate a meteoroid. They then fired it into a bag of water using a large gas-powered gun. The force of the gun mimics what happens when a nearby impact launches a rock into orbit, and the rapid deceleration and high pressures of hitting the water simulates smacking into the moon at high speeds.
The good news is that the impacts did not completely pulverize the fossils. None of them survived completely intact, but recognisable fragments were encouraging. Moon rocks brought back by lunar missions so far have not yielded any Earth fragments, but it's also true we haven't looked that hard.
We'll need to go back to the moon to prove any of this definitively. In any case, it's certainly fascinating to think of the moon littered with tiny bits of Earth, perfectly preserved for millions of years — an extraterrestrial archive of a bygone planet. [Philosophical Transactions of the Royal Society A via New Scientist]
Picture: Earthrise as seen from the moon. NASA