Earth fossils, such as ancient algae from the ocean, could survive on another planet or body in the solar system if they were in a meteorite, a new experiment finds. Since fossils can endure the extreme shock of the collision, researchers reason that fragments containing signs of ancient Earth life could be scattered across the moon right now.
Meteorites found on Earth that were created by impacts on the moon and Mars suggest that cosmic bodies regularly hurl rocks at each other, New Scientist explains. Some researchers have even claimed that Mars rocks -- in particular, Martian meteorite ALH84001 -- show signs of fossilized martian bacteria, though evidence of that is shaky. But, more fundamentally, "no one ever seems to have asked, even if the fossils did exist in a rock, would they survive?" says Mark Burchell from the University of Kent. If material could be successfully moved from one place to another, it stands to reason that they could be preserved in storage at their new home.
So, the trio of University of Kent researchers tried to simulate conditions that a rock would face on a trip from here to the moon. First, they created Earth meteoroids by mixing powdered rock with fossils, and then freezing it. Then they used a gun to fire projectiles containing the diatom fossils -- microscopic phytoplankton with silica walls -- at high speeds into a bag of water. Nine shots of the frozen fossils into the water target were carried out, at speeds ranging from 0.388 to 5.34 kilometers per second. These correspond to average peak pressures of 0.2 to 19 gigapascal (GPa). After that, the team filtered the water to look for the fossils from the projectile.
The tiny fossils survived the hypervelocity impact, but none of them survived perfectly intact. Being able to recover anything at all is promising, Burchell says. Earth’s geological activity could have easily destroyed rocks containing traces of ancient life, but they would be better preserved on the moon.
Above, you can see an electron image of diatoms, pre-shot. Here are some fragments that were trapped in debris from the shots at an impact speed of 3 kilometers per second. In the inset, red outlines the diatom and light blue indicates gun debris.
So far, neither robotic nor human explorers have found Earth meteorites on the moon. Our atmosphere and gravity might make it more difficult for rocks to leave, though it’s not impossible... fossils of early Earth could very well be on the moon or other planets, just waiting to be found.
The work was published in Philosophical Transactions of the Royal Society A this week.
Images: M.J. Burchell et al., 2014