Earth might once have resembled a hot, steamy doughnut

The newly proposed planetary shape is called a synestia

synestia illustration

PUFFED UP  Early in its development, a rocky planet may turn into a synestia (illustrated), a spinning disk of vaporized rock that looks like a jelly-filled doughnut with a small, solid core (gray).

S. Lock/Harvard Univ.

sin-es-ti-ə n.

A large spinning hunk of hot, vaporized rock that forms when rocky, planet-sized objects collide

Earth may have taken on a jelly doughnut shape early in its history. The rocky planet was spinning through space about 4.5 billion years ago when it smacked into a Mars-sized hunk of rotating rock called Theia, according to one theory (SN: 4/15/17, p. 18). That hit may have turned Earth into a synestia, a blob of mostly vaporized rock with an indented center, resembling a slightly squished jelly doughnut, new simulations suggest. This synestia wouldn’t have had much of a solid or liquid surface. And the structure could have spread to about 100,000 kilometers across or more, much larger than its original 13,000 kilo­meters or so. The added girth would have come from rock vaporizing and continuing to spin quickly, which would puff up and flatten the shape.

If Earth went through a synestia state, it was short-lived. An object Earth’s size would have quickly cooled and condensed back into a solid, spherical rock in 100 to 1,000 years, researchers write online May 22 in the Journal of Geophysical Research: Planets. Rocky bodies may become synestias several times before settling into a permanent planet shape, say planetary scientists Simon Lock of Harvard University and Sarah Stewart of the University of California, Davis. They came up with the term synestia from syn-, meaning together, and Hestia, the Greek goddess of home, hearth and architecture.

No one has seen a synestia in space. But the weird structures could be out there, waiting to be discovered in solar systems far away.

Ashley Yeager is the associate news editor at Science News. She has worked at The Scientist, the Simons Foundation, Duke University and the W.M. Keck Observatory, and was the web producer for Science News from 2013 to 2015. She has a bachelor’s degree in journalism from the University of Tennessee, Knoxville, and a master’s degree in science writing from MIT.

More Stories from Science News on Planetary Science