William Atkins
Friday, 10 April 2009 20:35
Science -
Space
Page 1 of 4
The Theia hypothesis, developed from the Giant Impact hypothesis, implies that the Moon was created when a Mars-sized planet (called Theia) crashed into the Earth 4.5 million years ago. Can we find Theia? The twin STEREO probes of NASA may piece together an answer.
Theia, sometimes called Thea or Thia, and also named Euryphaessa, is the mythological Greek Titan who gave birth to the Moon goddess Selene.
And, the Theia hypothesis is the dominant scientific hypothesis for the formation of the Moon, however, other hypotheses also exist such as the Moon forming at the same time as the Earth; the Moon forming elsewhere in the solar system but being captured by Earth’s gravitational field, and the Moon spinning off from centrifugal force of the rotating Earth.
However, most scientists contend that the Theia hypothesis makes the most sense. Check out the “
Big Splash” illustration showing the possible action by Theia taken out of its orbit and onto Earth.
The May 19, 2004 ArXiv article “
Where Did The Moon Come From?” by German-American theoretical mathematician
Edward Belbruneo and American astrophysicist
J. Richard Gott III, both from Princeton University, states,
“The current standard theory of the origin of the Moon is that the Earth was hit by a giant impactor the size of Mars causing ejection of iron poor impactor mantle debris that coalesced to form the Moon.”
They ask the question:
“But where did this Mars-sized impactor come from?”
And, answer:
“Isotopic evidence suggests that it came from 1AU (one astronomical unit, or rough distance between Sun and Earth) radius in the solar nebula and computer simulations are consistent with it approaching Earth on a zero-energy parabolic trajectory.”
They ask another question:
“But how could such a large object form in the disk of planetesimals at 1AU without colliding with the Earth early-on before having a chance to grow large or before its or the Earth's iron core had formed?”
The answer appears on page two.
