The Moon could have ancient Earth fossils scattered all across its surface
Tuesday, July 29, 2014, 11:45 AM - According to a new study, it's possible that fossils can make the journey between planets, and the Moon's surface may be littered with them from ancient impacts.
Billions of years ago, during a time when the planets and moons of the inner solar system were under heavy bombardment by asteroids and meteoroids, chunks of rock blasted away by these impacts were launched into space. We already have evidence of this happening, as some of these chunks made their way from Mars to Earth, and we have the meteorites to prove it. Undoubtedly there are chunks of Earth on both Mars and on the Moon (and possibly even further out, like Europa) that got there in this same way. While the evidence clearly points to the origin of these Martian meteorites, there has been some suggestion in recent years about the possibility that one or more of them might have fossilized microbes inside them, which apparently survived the journey from their point of origin. While the claims were dubious, at best, a team of researchers decided to test part of the hypothesis, by seeing if fossils actually could survive the journey between worlds.
Packing fossilized algae - known as diatoms - into chunks of ice, researchers from the University of Kent loaded these chunks into a rather large air cannon and fired them at high velocity into water targets.
According to their results, at 'low' speeds, just over one-third of a kilometre per second (or nearly 1,400 km/h), they found that these fossils, even larger specimens (up to 180 microns in size) were able to survive impact. As the speed increased past 1 km/s and up to 5 km/s and higher, they found no larger fossils intact, while smaller ones - around 30 to 40 microns in size - could still survive. The images to the right show diatoms after impacts of around 3 km/s, with each inset showing a colour-contrast version to reveal the diatom fragments in red (click the image to see the larger version).
While these speeds seem quite fast, they are very slow compared to the typical velocities for meteoroids, which average out at around 11 km/s (~40,000 km/h) when they hit the Earth's atmosphere or the surface of the Moon. However, according to the researchers, meteoroids that originate from Earth would be travelling much slower when they strike the Moon's surface, closer to the range they tested.
"In the case of material ejected from the Earth striking the Moon, the impact speeds are lower still, peaking at approximately 3 km s−1," they wrote in their study. "This, in turn, leads to lower peak shock pressures (estimated in the range 1–20 GPa depending on the materials and impact speed). There may thus be extensive survival of terrestrial materials on the Moon."