Shop Windows to the Universe

Earth Science Rocks! Select one of our four cool NESTA t-shirts from our online store, and express your love of Earth and space science!
This is an illustration of the Chicxulub impact.
Click on image for full size
NASA/JPL

The Collisional Ejection Theory

Currently, the theory that best explains all the evidence is the collisional ejection theory. This theory holds that the Moon formed from debris ejected from the Earth when a large object (possibly as large as Mars) crashed into the Earth. Simulations of this scenario show that energy from such a collision produces a stream of vaporized rock from the impact. The Moon forms from this cooled material.

This theory explains many of the known properties of the Moon's orbit and composition. The ejected material would have coalesced in or near the ecliptic plane, putting the Moon into an orbit much like the one it has. The Moon, which is believed to have a small iron core, could have retained this core through the collision. Volatile elements would have been vaporized during the impact. Also, this collision could have tipped the Earth's axis, causing the seasons we now know.

The problem with this theory is that it does not seem very likely.

Shop Windows to the Universe Science Store!

Our online store includes issues of NESTA's quarterly journal, The Earth Scientist, full of classroom activities on different topics in Earth and space science, as well as books on science education!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Element (Chemical Element)

An element (also called a "chemical element") is a substance made up entirely of atoms having the same atomic number; that is, all of the atoms have the same number of protons. Hydrogen, helium, oxygen,...more

Charon - Pluto's biggest moon

Charon is a moon of Pluto. Pluto has // Call the moon count function defined in the document head print_moon_count('pluto'); moons. Charon is much larger than Pluto's other moons. James Christy discovered...more

The Co-Formation Theory

The co-formation theory explains the origin of the moon as an object which formed out of the primitive solar nebula at the same time and roughly the same place as the Earth. As shown in this picture, while...more

The Lunar Atmosphere

People used to think that moons such as the Earth's moon or the moons of Jupiter had no atmosphere whatsoever. Now, however, measurements have shown that most of these moons are surrounded by a *very*...more

The Moon's Magnetosphere

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

The Many Names for the Full Moon

Sometimes, in the fall, you may hear people call a Full Moon the "Harvest Moon". That's because farmers can stay in their fields late, after sunset, harvesting their crops by the bright light of a Full...more

Altocumulus

Altocumulus clouds are part of the Middle Cloud group (2000-7000m up). They are grayish-white with one part of the cloud darker than the other. Altocumulus clouds usually form in groups and are about...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF