Please do not remove this tag or merge the pages until a decision has been made.
Theia is a hypothetical planetary body proposed to have existed in the early Solar System. According to the widely accepted Giant-impact hypothesis, Theia collided with the early Earth approximately 4.5 billion years ago, leading to the formation of the Moon. This impact is considered one of the most significant events in Earth's geological and astronomical history.[1]
Characteristics
Theia is thought to have been a Mars-sized protoplanet, with an estimated diameter of about 6,000–8,000 kilometers. It likely formed in a Lagrange point of the proto-Earth's orbit, a region of relative gravitational stability. The orbital resonance with the proto-Earth eventually destabilized, leading to the collision.[2]
Theia's composition is believed to have been similar to that of Earth and other terrestrial planets in the inner Solar System, consisting primarily of silicate rock and metal. This similarity is supported by isotopic evidence from lunar rocks, which share nearly identical oxygen isotope ratios with Earth's mantle.[3]
The Giant-impact hypothesis
Main Article: Giant-impact hypothesis
The Giant-impact hypothesis suggests that Theia collided with the proto-Earth at a glancing angle. The impact ejected vast amounts of debris into orbit around Earth, which eventually coalesced to form the Moon. The energy released by the collision significantly altered Earth's rotation, tilt, and composition, contributing to the planet's differentiation into a metallic core and silicate mantle.[4]
The hypothesis is supported by several lines of evidence:
- Isotopic Similarity: Lunar rocks returned by the Apollo missions have isotopic compositions almost identical to those of Earth's mantle, indicating a shared origin.[5]
- Moon's Low Iron Content: The Moon has a lower iron content compared to Earth, consistent with material derived primarily from Earth's mantle and Theia's outer layers.[6]
- Computer Simulations: Numerical models of the impact scenario reproduce the observed properties of the Earth-Moon system, including the Moon's mass and orbit.[7]
Fate of Theia
Most of Theia's material is believed to have been absorbed by Earth or incorporated into the Moon. The remnants of Theia's core likely merged with Earth's core, contributing to its current size and density.[8]
Controversies and Alternative Theories
While the Giant-impact hypothesis is widely accepted, some questions remain unresolved. For example, the near-identical isotopic composition of Earth and the Moon suggests that the debris cloud from the collision was thoroughly mixed, which is difficult to explain with simple impact scenarios. Alternative theories, such as multiple smaller impacts or a synestia (a rapidly spinning, donut-shaped mass of vaporized rock), have been proposed to address these issues.[9]
Trivia
- Theia has been widely regarded as the object that formed the moon.
- Theia was most likely an Earth trojan, before colliding with Earth.
- Theia's page used to be the target of mass vandalism by Fandom users, who are much disliked by the Solar System Wiki.
- The largest edit in terms of byte size was made on this page on August 20, 2023. The edit was over 2 megabytes in size. See the edit here.
- The original image that was used to represent Theia on this page used to depict a random brown rocky planet with a set of craters on its surface. In actuality, Theia wouldn't really have had the time to cool down that fast and wouldn't have been able to support an atmosphere with clouds during its formation and eventual collision with Earth. The image was eventually changed to a more accurate depiction of what Theia would look like.
- Similar to what happened with Tarqeq, Theia's original image became somewhat of a popular depiction of the planet.
| Solar System Wiki Register of Historical Content | |
|---|---|
| Inducted for wiki cultural impact | |
| Vandalism of Theia (Before Move) • Tarqeq Face Troll (Tarqeq Face) • Old Wiki Main Page • Wiki-wordmark.png (Old wiki logo) • User:MrScience12 | |
| Inducted as milestone pages | |
| 599px-The Earth seen from Apollo 17.jpg (First file) • Earth (First page) • Category:Planets (First category) • Template:Isonoe (First template) | |
Gallery
References
- ↑ https://www.nhm.ac.uk/discover/how-did-the-moon-form.html#:~:text=Before%20Earth%20and%20the%20Moon,history%2C%20these%20two%20bodies%20collided.&text=During%20this%20massive%20collision%2C%20nearly,'
- ↑ https://www.astronomy.com/science/theia-slammed-into-earth-left-marks-and-then-formed-the-moon-study-suggests/
- ↑ https://science.nasa.gov/moon/formation/#:~:text=Earth's%20Moon%20is%20thought%20to,space%20that%20became%20the%20Moon.
- ↑ https://www.vaia.com/en-us/textbooks/geography/earth-portrait-of-a-planet-5-edition/chapter-1/problem-12-describe-how-the-moon-was-formed/#:~:text=The%20Giant%20Impact%20Hypothesis%2C%20also,coalesced%20to%20form%20the%20Moon.
- ↑ https://science.nasa.gov/moon/formation/#:~:text=Perhaps%20most%20importantly%2C%20the%20rock,to%20the%20top%20of%20magma.
- ↑ https://science.nasa.gov/moon/formation/
- ↑ https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JE005098#:~:text=Giant%20Impact%20simulations%20are%20becoming,used%20to%20constrain%20disk%20models.
- ↑ https://www.caltech.edu/about/news/the-remains-of-an-ancient-planet-lie-deep-within-earth#:~:text=This%20new%20study%20suggests%20that%20most%20of,from%20the%20impact%20coalesced%20into%20the%20Moon.&text=The%20researchers'%20simulations%20showed%20that%20much%20of,than%20estimated%20by%20earlier%2C%20lower%2Dresolution%20impact%20models.
- ↑ https://www.researchgate.net/publication/347165865_A_History_of_a_Ruling_Paradigm_in_the_Earth_and_Planetary_Sciences_That_Guided_Research_for_Three_Decades_The_Giant_Impact_Model_for_the_Origin_of_the_Moon_and_the_Earth-Moon_System