3 ms·

Geologist here -- this has been an active topic lately! Just a few weeks ago there was a paper proposing a 4.336 +/- 0.031 Ga age for the Lunar Magma Ocean [1]

Geologist here -- this has been an active topic lately! Just a few weeks ago there was a paper proposing a 4.336 +/- 0.031 Ga age for the Lunar Magma Ocean [1], which is often equated with (esp. in public press [e.g., 2], though not really the same as) the age of the Moon. For comparison, the "40 to 60 Ma after solar system formation" in the new paper [3] discussed here translates into roughly 4.517 +/- 0.010 Ga. This new paper agrees almost perfectly with one I was a coauthor on a couple years ago though [4], which also gave an age of 4.51 (+/- 0.01) Ga, so maybe we're starting to get slightly closer to some consensus. [1] https://doi.org/10.1016/j.epsl.2019.07.008 https://doi.org/10.1016/j.epsl.2019.07.008 [2] https://www.newscientist.com/article/mg21128265-100-moon-may-be-200-million-years-younger-than-thought/ https://www.newscientist.com/article/mg21128265-100-moon-may... [3] https://www.nature.com/articles/s41561-019-0398-3 https://www.nature.com/articles/s41561-019-0398-3 [4] https://advances.sciencemag.org/content/3/1/e1602365 https://advances.sciencemag.org/content/3/1/e1602365

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xefer 7y ago
How is the time of "solar system formation" defined? Presumably a system slowly forms out of gas and dust but at what point does the accumulating material cross some threshold to where it is considered a new system? Solar ignition?
- xefer 7y ago
  I found this reference in which the abstract provides this definition: "The age of the Solar System can be defined as the time of formation of the first solid grains in the nebular disc surrounding the proto-Sun" https://doi.org/10.1038/ngeo941 https://doi.org/10.1038/ngeo941 "The age of the Solar System can be defined as the time of formation of the first solid grains in the nebular disc surrounding the proto-Sun. This age is estimated by dating calcium–aluminium-rich inclusions in meteorites. These inclusions are considered as the earliest formed solids in the solar nebula. Their formation marks the beginning for several long- and short-lived radiogenic clocks that are used to precisely define the timescales of Solar System events, such as the formation and evolution of planetary bodies1,2,3. Here we present the 207Pb–206Pb isotope systematics in a calcium–aluminium-rich inclusion from the Northwest Africa 2364 CV3-group chondritic meteorite, which indicate that the inclusion formed 4,568.2 million years ago."
  - cbkeller 7y ago
    Yeah, that's it -- since the first solid material also means the first material we can determine an age of!

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xefer 7y ago

How is the time of "solar system formation" defined? Presumably a system slowly forms out of gas and dust but at what point does the accumulating material cross some threshold to where it is considered a new system? Solar ignition?

xefer 7y ago
I found this reference in which the abstract provides this definition: "The age of the Solar System can be defined as the time of formation of the first solid grains in the nebular disc surrounding the proto-Sun" https://doi.org/10.1038/ngeo941 https://doi.org/10.1038/ngeo941 "The age of the Solar System can be defined as the time of formation of the first solid grains in the nebular disc surrounding the proto-Sun. This age is estimated by dating calcium–aluminium-rich inclusions in meteorites. These inclusions are considered as the earliest formed solids in the solar nebula. Their formation marks the beginning for several long- and short-lived radiogenic clocks that are used to precisely define the timescales of Solar System events, such as the formation and evolution of planetary bodies1,2,3. Here we present the 207Pb–206Pb isotope systematics in a calcium–aluminium-rich inclusion from the Northwest Africa 2364 CV3-group chondritic meteorite, which indicate that the inclusion formed 4,568.2 million years ago."
- cbkeller 7y ago
  Yeah, that's it -- since the first solid material also means the first material we can determine an age of!