This drawing illustrates how forming moons drew gas to themselves.
Image from: The New Solar System
The Co-Formation Theory
The co-formation theory explains the origin of the moon as an object which formed out of the initial cloud of gas and dust
at the same time and roughly the same place as the Earth. As shown in this picture, while they were forming in the solar nebula, the beginning of the moons-to-be (called protomoons) drew material
to themselves from the cloud of gas and dust around them.
Because the proto-moon was so close to the proto-earth the gas out of which they both formed ought to be very similar, composed mostly of something which would form rock.
The co-formation theory explains why the moon appears in the location it does but it does not explain the evidence that the Earth and Moon do not appear to be made of the same stuff.
Shop Windows to the Universe Science Store!
Learn about Earth and space science, and have fun while doing it! The games
section of our online store
includes a climate change card game
and the Traveling Nitrogen game
You might also be interested in:
The position of the planets in the solar nebula affected how big they became and what they were made of. The blue line in the picture shows where it became so cold that ice began to form. Planets that...more
The co-formation theory explains the origin of the moon as an object which formed out of the initial cloud of gas and dust at the same time and roughly the same place as the Earth. As shown in this picture,...more
People used to think that moons such as the Earth's moon had no atmosphere whatsoever. Now, however, measurements have shown that most of these moons are surrounded by a *very* thin region of molecules...more
Unlike the Earth, which has a protective shield around it called the magnetosphere, the surface of the moon is not protected from the solar wind. This picture shows the magnetosphere surrounding the Earth,...more
Do you know anybody who has a nickname? Did you know that the Full Moon has a bunch of nicknames? Native Americans who lived in the North and East parts of North America had many nicknames for the Full...more
Altocumulus clouds are part of the Middle Cloud group. They are grayish-white with one part of the cloud darker than the other. Altocumulus clouds usually form in groups. Altocumulus clouds are about...more
Altostratus clouds belong to the Middle Cloud group. An altostratus cloud usually covers the whole sky. The cloud looks gray or blue-gray. The sun or moon may shine through an altostratus cloud, but will...more