The striking image on the cover of the latest issue of Philosophical Transactions A provides an artist’s impression of the giant impact that scientists believe created the Moon. Published online today, the issue summarises the current state of our understanding about the origin of the Moon, and looks at the challenges that still remain.

moon origin


The image, which comes courtesy of William K. Hartmann at the Planetary Science Institute, Tucson, is an acrylic painting providing a visualization of conditions approximately one hour after a giant impact between the Earth and another planetary body (often called Theia) 4.5 billion years ago, based on numerical modeling results. The model involves a near tangential impact, which has sheared off parts of the proto-Earth (right) and the impactor. The impactor, now slowed, begins to loop around toward a second impact, in a chaos of incandescent material. So great was the impact, that it left the Earth in a molten state, taking almost 10 million years to solidify.

In addition to contributing a remarkable cover image, William Hartmann also provides the opening article in the issue – a discussion of the past, present and future of the giant impact hypothesis, which you can access for free until the end of August.

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