According to the hypothesis of huge impacts, the Earth-Moon system was created roughly 4.5 billion years ago when the Earth object collided with a great deal of Mars. This impact has led to the release of a massive amount of material that eventually merged to create the Earth and the Moon. In time, the Moon gradually moved from Earth to take over its current orbit.
Since then, there have been regular exchanges between the Earth and the Moon due to the effects on their surface. According to a recent study, the impact came during Hadean Eon (roughly 4 billion years ago) could be responsible for sending the Earth's oldest sample of the earth to the moon where it received it Apollo 14 astronauts.
A study that has recently appeared in the journal Earthly and planetary scientific letters, led by Jeremy Bellucci of the Swedish Museum of Natural History, including members of the Lunar and Planetary Institute (LPI), several universities and the Center for Science and Research of Lunar Sciences (CLSE), part of the NASA Solar Research Research Virtual Institute.
This discovery was made possible by the new technology developed by the study team to locate fragments of the impactor in the lunar regolith. The development of this technique was led by Dr. David A. Kring – CLSE Chief Investigator and USRA Research Scientist at LPI – and invited them to discover a piece of Earth on the Moon.
The resulting investigation led to a 2 g (0.07 oz) fragment of rock composed of quartz, feldspar and zircon. Rocks of this type are commonly found on Earth, but on the Moon they are very unusual. In addition, chemical analysis has shown that the rock crystallized in the oxidized system and at the Earth's corresponding temperatures during Hadean; rather than the Moon, which at that time experienced higher temperatures.
As Dr. Kring in a recent LPI press release:
"It's an extraordinary finding that helps paint a better image of the early Earth and the bombing that has changed our planet during the dawn of life."
Based on their analysis, they came to the conclusion that the rock was created in Hadean Eon and was launched from Earth when a large asteroid or comet hit the surface. This impact could push the material into the space where it collided with the surface of the Moon, which at that time was three times closer to Earth. Finally, this rock material blended with the lunar regolite and created a single sample.
The team also learned from their analysis about the history of the sample rock. One concluded that the rock had crystallized at a depth of about 20 km (12.4 mi) below the earth's surface between 4.0. and 4.1 billion years ago, and then it was dug by one or several major impacts that sent it to the cis-lunar space.
This is in line with previous team research that showed how the impacts during this period – ie, heavy bombing (which took place between 4.1 and 3.8 billion years) – produced craters with a diameter of thousands of kilometers, which was more than enough to eject the material from a depth of 20 km (12.4 mi) into space.
They also found that several other impact events affected it as soon as it reached the lunar surface. One of them caused the sample to partially melt about 3.9 billion years ago, and could have buried it under the surface. After this period, the Moon was exposed to influences that were less and less common and gave it the surface it has today.
The final impact event that affected this sample occurred about 26 million years ago during the Paleogenetic period on Earth. This impact caused a crater with a diameter of 340 m (1082 ft) and leapt specimen rock back to the moon surface. This crater was the landing site Apollo 14 mission in 1971, where mission astronauts took samples of the rocks to return to Earth for study (which included Earth Rock).
The research team recognizes that it is possible that the sample could crystallize on the moon. This would, however, require conditions that have not yet been observed in previously obtained samples of the month. For example, the sample would have to crystallize very deep inside the lunar cloak. It is further assumed that the composition of the Moon at these depths is completely different from what was observed in the sample rock.
As a result, the easiest explanation is that it is a terrestrial rock that has been set up on the moon, a finding that is likely to cause some disputes. This is unavoidable because it is the first Hadean's sample of its kind to be found, and the place of its discovery is also likely to add to the infidelity factor.
Kring, however, expects more samples to be found, as the Hadean rocks are likely to pepper the moon's surface during late heavy bombing. Perhaps when crew crews begin to travel to the moon in the next decade, they will have a chance on more of the oldest earth rock samples.
Research was made possible by NASA's Solar Research Exploration Research (SSERVI), part of NASA's joint venture LPI and Space Center Johnson Space Center.