1. Magma Ocean Solidification: Oldest Lunar Zircon COSMOCHEMISTRY iLLUSTRATED Time to Solidify an Ocean of Magma The Moon melted when it formed. How long did it take this ocean of magma to solidify?

2. Magma Ocean Solidification: Oldest Lunar Zircon COSMOCHEMISTRY iLLUSTRATED Time to Solidify an Ocean of Magma Aftermath of the giant impact: Rapid, hot formation of the Moon. Magma ocean cooling began soon after lunar formation. Measurements of Sm-Nd and W isotopes indicate lunar formation occurred 4.517 billion years ago.

3. Magma Ocean Solidification: Oldest Lunar Zircon COSMOCHEMISTRY iLLUSTRATED Time to Solidify an Ocean of Magma Rock 72215 collected at Apollo 17 site. A single zircon in 72215 shows a range of ages. The oldest cluster at 4.417 billion years. This is 100 million years after Moon magma ocean began to crystallize.

4. Magma Ocean Solidification: Oldest Lunar Zircon COSMOCHEMISTRY iLLUSTRATED Time to Solidify an Ocean of Magma Nemchin et al. (2009) Oldest zircons have an average 207Pb/ 206 Pb age of 4.417 Ga, likely close to the end of magma ocean crystallization.

5. Magma Ocean Solidification: Oldest Lunar Zircon COSMOCHEMISTRY iLLUSTRATED End of Magma Ocean Crystallization Origin of Moon at 4.517 billion years ago Formation of much of the anorthosite crust (crystallization 75% completed), 61 million years later (4.456 Gy) End of crystallization (maybe a few percent magma left over), 39 million years later (4.417 Gy) Magma ocean duration:  100 My