Impact heating and the hidden Hadean.
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| Title: | Impact heating and the hidden Hadean. |
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| Authors: | Johnson, Tim E. (AUTHOR), O'Neill, Craig (AUTHOR), Turner, Simon (AUTHOR), Kirkland, Christopher L. (AUTHOR) |
| Source: | Science. 6/25/2026, Vol. 392 Issue 6805, p1408-1412. 5p. |
| Subjects: | Hadean, Crust of the earth, Heat engineering, Earth (Planet), Geodynamics, Continental crust |
| Abstract: | The nature of Earth's crust during the Hadean eon [≥4.03 billion years ago (Ga)] is uncertain. Numerical models of early Earth geodynamics emphasize the control of mantle temperature but generally consider only internally derived heat, despite empirical evidence for an intense Hadean impact flux. Using a stochastic model of that flux, we show that the time-integrated heat due to impacts would have dwarfed that produced internally throughout the Hadean. Earth's Hadean crust would have been extensively molten at depths below a few kilometers, causing gravitational segregation of dense, iron- and magnesium-rich material and driving average crustal compositions to become increasingly silica rich. Globally, impact heating would have become much less important after 3.9 Ga, allowing the crust to thicken. That enduring continental crust appeared around this time is likely not a coincidence. Editor's summary: There are few crustal remnants from Earth's first 500 million years. The delayed generation and preservation of the crust has been mostly linked to early tectonic modes, as driven by internal heat. Impacts, however, would have also raised the temperature, a process Johnson et al. modeled based on rescaled lunar flux in one- and two-dimensional geodynamic simulations (see the Perspective by Yuan). Their results showed that until about 4.0 billion years ago, the heat from impacts was at least an order of magnitude higher than the internal heat and was capable of keeping the crust thin and partially molten at depths of just a few kilometers. —Angela Hessler [ABSTRACT FROM AUTHOR] |
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| Database: | Psychology and Behavioral Sciences Collection |
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| Abstract: | The nature of Earth's crust during the Hadean eon [≥4.03 billion years ago (Ga)] is uncertain. Numerical models of early Earth geodynamics emphasize the control of mantle temperature but generally consider only internally derived heat, despite empirical evidence for an intense Hadean impact flux. Using a stochastic model of that flux, we show that the time-integrated heat due to impacts would have dwarfed that produced internally throughout the Hadean. Earth's Hadean crust would have been extensively molten at depths below a few kilometers, causing gravitational segregation of dense, iron- and magnesium-rich material and driving average crustal compositions to become increasingly silica rich. Globally, impact heating would have become much less important after 3.9 Ga, allowing the crust to thicken. That enduring continental crust appeared around this time is likely not a coincidence. Editor's summary: There are few crustal remnants from Earth's first 500 million years. The delayed generation and preservation of the crust has been mostly linked to early tectonic modes, as driven by internal heat. Impacts, however, would have also raised the temperature, a process Johnson et al. modeled based on rescaled lunar flux in one- and two-dimensional geodynamic simulations (see the Perspective by Yuan). Their results showed that until about 4.0 billion years ago, the heat from impacts was at least an order of magnitude higher than the internal heat and was capable of keeping the crust thin and partially molten at depths of just a few kilometers. —Angela Hessler [ABSTRACT FROM AUTHOR] |
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| ISSN: | 00368075 |
| DOI: | 10.1126/science.aeb5402 |
