The real 1%: Volatiles in planetary accretion and the rapid development of habitability
Lindy Elkins-Tanton DTM, Carnegie Institution
Elkins-Tanton What period of time are we talking about? 542 542 Ediacaran Ediacaran 630 First appearance of Ediacaran Fauna Major ice ages
Neo- Cryogenian First appearance of metazoans and glacial deposits
proterozoic 13 850 First appearance of δ C anomalies
1000
Environment stability; ‘Rodinian’ reducing deep oceans
1500 Mesoproterozoic
First appearance of sulphidic 1780 marine deposits
Proterozoic Supercontinent formation ‘Columbian’ (Columbia/Nuna) 2000 2060 End of LJE / Start of shungite deposition ‘Jatulian’/ Lomagundi-Jatuli isotopic excursion ‘Eukaryian’ 13 2250 First appearance of +ve δ C anomalies +/or breakout magmatism
Paleoproterozoic ‘Oxygenian’ Glaciations; rise in atmospheric O2 2420 First appearance of glacial deposits 2500 Siderian Deposition of BIF; waning continental growth 2630 First appearance of Hamersley BIF ‘Methanian’ Major crustal growth and recycling Neoarchean First appearance of continental flood 2780 13 basalts and/or +ve δ C kerogen values ‘Pongolan’ Basin deposition on stable continents 3000 3020 First appearance of terrestrial basins Archean Growth of stable continental nuclei; ‘Vaalbaran’ oldest macroscopic evidence for life Mesoarchean
3490 First appearance of macroscopic 3500 fossils (stromatolites) First preserved sedimentary rocks, ‘Isuan’ with chemical traces of life
3810 Earth's oldest supracrustal rocks Oldest preserved pieces of continental crust
Paleoarchean ‘Acastan’ 4000 4030 Earth’s oldest rocks (Acasta Gneiss)
Rapid crust formation and recycling; continued heavy meteorite bombardement
‘Jack Hillsian’ or ‘Zirconian’ Earth’s oldest crustal material 4404 (detrital zircons) Accretion of giant Moon-forming Hadean 4500 ‘Chaotian’ impact event 4568 Formation of the solar system Van Kranendonk
Fig16.29 542 Ediacaran Ediacaran 630 First appearance of Ediacaran Fauna Major ice ages
Neo- Cryogenian First appearance of metazoans and glacial deposits
proterozoic 13 850 First appearance of δ C anomalies
1000
Environment stability; ‘Rodinian’ reducing deep oceans
1500 Mesoproterozoic
First appearance of sulphidic 1780 marine deposits
Proterozoic Supercontinent formation ‘Columbian’ (Columbia/Nuna) 2000 2060 End of LJE / Start of shungite deposition ‘Jatulian’/ Lomagundi-Jatuli isotopic excursion ‘Eukaryian’ 13 2250 First appearance of +ve δ C anomalies +/or breakout magmatism
Paleoproterozoic ‘Oxygenian’ Glaciations; rise in atmospheric O2 2420 First appearance of glacial deposits 2500 Siderian Deposition of BIF; waning continental growth 2630 First appearance of Hamersley BIF ‘Methanian’ Major crustal growth and recycling Neoarchean First appearance of continental flood 2780 13 basalts and/or +ve δ C kerogen values ‘Pongolan’ Basin deposition on stable continents 3000 3020 First appearance of terrestrial basins Archean Growth of stable continental nuclei; ‘Vaalbaran’ oldest macroscopic evidence for life Mesoarchean
3490 First appearance of macroscopic 3500 fossils (stromatolites) First preserved sedimentary rocks, ‘Isuan’ with chemical traces of life
3810 Earth's oldest supracrustal rocks Oldest preserved pieces of continental crust
Paleoarchean ‘Acastan’ 4000 4030 Earth’s oldest rocks (Acasta Gneiss)
Rapid crust formation and recycling; continued heavy meteorite bombardement
‘Jack Hillsian’ or ‘Zirconian’ Earth’s oldest crustal material 4404 (detrital zircons) Accretion of giant Moon-forming Hadean 4500 ‘Chaotian’ impact event 4568 FirstFormation solids inof thethe protoplanetarysolar system disk
Fig16.29
Van Kranendonk How do rocky planets obtain atmospheres?
1. Capture of nebular gases
2. Degassing from the interior
3. Later surface impacts What material are we working with? Lodders (2003) Data from Jarosewich (1990) Data from Jarosewich (1990) What processes make planets? Elkins-Tanton (2012) Ann.Rev. 1693: Leibniz suggests in his book Protogaea that the Earth was once molten
Gottfried Wilhelm Leibniz Bibliothek, Hannover Planets retain volatiles during accretion
• Moon, Mars, Mercury
• Water, carbon, …, helium!
NASA Elkins-Tanton. Some volatiles inside, some volatiles outside. The maximum water capacities of mantle minerals vary widely
Elkins-Tanton Maximum bulk water content retained in planetary mantle
Elkins-Tanton H O 2 Kind of meteorite: Dominant atmospheric specie
CM: H2O CI: H2O
LL: H2 H: H2
EH: H2 L: H2
CV: CO2 EL: CO Carbon Current day: N2 N2 Species Earliest degassed atmospheres vary with oxidation state, and all are a long way from current day
DATA from Schaefer and Fegley (2010), Hashimoto et al. (2007), Elkins-Tanton and Seager (2008) New York Times (2008) Life (1952) 0.7 H chondrites Carbonaceous chondrites Achondrites 0.6 L chondrites Enstatite chondrites
0.5 30 km deep ocean LL chondrites 0.4
0.3 Water [wt%] Water
0.2
0.1 5 km deep ocean
0.0 0.0 0.1 0.2 0.3 0.4 Carbon[wt%] Earth starting with 100 ppm bulk water produces dense atm that collapses upon cooling into global ocean 100s m deep Elkins-Tanton ; Data from Jarosewich (1990) Elkins-Tanton (2012) Ann.Rev. Elkins-Tanton (2010)