The newly proposed planetary shape is called a synestia
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.
S. Lock. The structure of terrestrial bodies: Impact heating, corotation limits, and synestias. Journal of Geophysical Research: Planets. Published online May 22, 2017. doi: 10.1002/2016JE005239.
A. Yeager. Watery exoplanet’s skies suggest unexpected origin story. Science News. Vol. 191, June 10, 2017, p.11.
T. Sumner. Competing ideas abound for how Earth got its moon. Science News. Vol. 191, April 15, 2017, p. 18.