Synonyms
Definition
Theia is the name given to a hypothetical protoplanet or planetesimal, roughly the size of Mars, which is thought to have collided with the proto-Earth, ejecting material into orbit to form the Moon. The hypothesis of Moon formation by Theia is called the “Moon-forming Giant Impact hypothesis.”
Overview
The impactor’s name comes after the mythical Greek goddess Theia who gave birth to the Moon goddess, Selene. The most widely accepted model for the Moon origin is that Theia struck the proto-Earth at an oblique angle, adding 10% of the Earth’s mass and generating a hot, partly vaporized debris disc from which the Moon accreted (Canup and Asphaug 2001). The timing of the impact and the nature of the impactor have been the focus of numerous studies and speculations, not completely solved.
The timing of the impact could be solved either precisely determining the age of the Moon (Halliday 2008) or the age of the Earth’ core differentiation, if the impact...
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References and Further Reading
Avice G, Marty B (2014) The iodine–plutonium–xenon age of the Moon–Earth system revisited. Philos Trans R Soc A 372:20130260
Canup RM, Asphaug E (2001) Origin of the Moon in a giant impact near the end of the Earth’s formation. Nature 412:708–712
Halliday AN (2008) A young Moon-forming giant impact at 70–110 million years accompanied by late-stage mixing, core formation and degassing of the Earth. Philos Trans R Soc A 366:4163–4181
Herwartz D, Pack A, Friedrichs B, Bischoff A (2014) Identification of the giant impactor Theia in lunar rocks. Science 344:1146–1150
Jacobson SA, Morbidelli A, Raymond SN, O’Brien DP, Walsh KJ, Rubie DC (2014) Highly siderophile elements in Earth’s mantle as a clock for the Moon-forming impact. Nature 508:84–87
Further Reading
Hartmann WK (2014) The giant impact hypothesis: past, present (and future?). Philos Trans R Soc A 372:20130249
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Pinti, D.L. (2022). Theia. In: Gargaud, M., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-27833-4_1578-4
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DOI: https://doi.org/10.1007/978-3-642-27833-4_1578-4
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