What is the Center for Lunar Origin and Evolution Doing?
The Center for Lunar Origin and Evolution — or CLOE — team will help us understand more about how our Moon formed and changed in its early history. They are studying two things in particular:
1.) Formation of Our Moon. The Giant Impact Theory, the current scientific theory for the formation of our Moon, proposes that a huge protoplanet, about half the size of Earth, smashed into Earth around 4.5 billion years ago. This impact would have created a ginormous disk of molten rock and vapor — some from the impactor and some from Earth — around Earth.
The physics of the disk (motion, temperature) controls what compositions of materials, and how much material, ends up where. Some of the material would return to Earth, some would be lost to space, and the rest would form the Moon. The physics also controls how hot the newly formed Moon would be. The slamming together of debris to form the Moon might create enough heat to melt the outer surface of the Moon, or perhaps the entire Moon! To untangle the physics — and to test the Giant Impact Theory — the CLOE team will use powerful computer models and information about the chemistry of early Earth and Moon rocks from other NLSI teams. With their models, the CLOE team will help us figure out how - or even if it is possible — the disk evolved into the Moon we see today.
2.) History of Impacts on Our Moon. Several large lunar basins — the big dark circles you see when you look at the Moon — have ages of about 4.0 to 3.8 billion years. One scientific theory is that a Late Heavy Bombardment occurred at this time, with huge asteroids striking the Moon’s surface and the surfaces of other planets and Moons in our solar system. Scientists want to know if this was just a time when planet-making was winding down across our solar system, or if this was a sudden spike in impacts.
To help figure out which theory is correct, the CLOE team will develop computer models to explore how different rates of impacts might have influenced the Moon. Their models will use new information about how comet and asteroid populations have changed since the formation of our solar system — how they may have moved around in the solar system and may have broken up, creating showers that impacted Earth, the Moon, and other planetary bodies. They also will use information from CLOE team members who are analyzing the chemistries and ages of early Earth and Moon rocks and who are studying new images of craters on the Moon's surface to create a timeline of impacts.
One of the really neat models that the CLOE team is testing is whether or not a sudden shift of the gas giants into the outer parts of the solar system triggered the Late Heavy Bombardment. Some gas giants may have even changed places! The shift would have upset the population of asteroids and comets in this outer region, causing them to scatter and creating a solar-system wide bombardment by these impactors.