Did the Moon or planets form in a manner similar to that of Earth?
Did the moon or planets accrete in ways similar to Earth, in the same time frame, or both? How do the accretion histories of the moon and other planets compare with that of Earth?
It is unlikely that the moon formed in the same way as earth, i.e., as a rocky core in orbit around the juvenile sun, accreting material from debris in the young solar system. A more likely scenario is the moon as a by-product of an impact between early earth (after the core had formed, but before earth had fully accreted) and a Mars-sized rocky body.
Planets between the sun and the asteroid belt are all composed largely of silicate rocks. That is, most of their mass consists of elements and compounds that vaporize at "very high" temperatures. All such terrestrial planets formed in similar ways, leading to similar vertical layers within them (typically core, mantle, and crust). But the material that accreted to make them varied somewhat, possibly in narrow bands, with distance from the young sun. A good example is the difference in the K/Th mass fraction ratio as well as in the mass fraction of Fe between Earth and Mars.
Clear and detailed descriptions of the origin of the moon are available at the following sites:
Issues with the impact-origin theory is highlighted in a well-cited Wikipedia entry as well.
Two additional concise but insightful descriptions on the origin of the moon are available at:
Get More 'Curious?' with Our New PODCAST:
- Podcast? Subscribe? Tell me about the Ask an Astronomer Podcast
- Subscribe to our Podcast | Listen to our current Episode
- Cool! But I can't now. Send me a quick reminder now for later.
How to ask a question:
If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist
This page has been accessed 9634 times since September 19, 2007.
Last modified: September 19, 2007 8:26:27 PM
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.
Warning: Your browser is misbehaving! This page might look ugly. (Details)