University or Bern | 2019 Oct 09
A hot, molten Earth would be around 5% larger than its solid counterpart. This is the result of a study led by researchers at the University of Bern. The difference between molten and solid rocky planets is important for the search of Earth-like worlds beyond our Solar System and the understanding of Earth itself.Artist’s impression of the interior of a hot, molten rocky planet (with labels).
© University of Bern, illustration: Thibaut Roger
Rocky exoplanets that are around Earth-size are comparatively small, which makes them incredibly difficult to detect and characterise using telescopes. What are the optimal conditions to find such small planets that linger in the darkness? “A rocky planet that is hot, molten, and possibly harboring a large outgassed atmosphere ticks all the boxes,” says Dan Bower, astrophysicist at the Center for Space and Habitability (CSH) of the University of Bern. Such a planet could be more easily seen by telescopes due to strong outgoing radiation than its solid counterpart. The SNSF Ambizione and CSH Fellow continues: “Granted, you wouldn’t want to vacation on one of these planets, but they are important to study since many if not all rocky planets begin their life as molten blobs, yet eventually some may become habitable like Earth.
Rocky planets are built from the leftovers of the leftovers. “Everything that doesn’t make its way into the central star or a giant planet has the potential to end up forming a much smaller terrestrial planet,” says Bower: “We have reason to believe that processes occurring during the baby years of a planet’s life are fundamental in determining its life path.” Therefore, Bower and a team of post-docs - dominantly from within the PlanetS network - were intrigued to uncover the observable nature of such a planet. Their study is now published in the journal Astronomy & Astrophysics. It shows that a molten Earth would actually be around 5% larger in radius than a solid Earth, and this is due to the difference in the behavior of molten versus solid materials at the extreme conditions of a planetary interior. “In essence, a molten silicate occupies more volume than its equivalent solid, and this increases the size of the planet,” Bower explains. ...
Linking the Evolution of Terrestrial Interiors and an Early Outgassed
Atmosphere to Astrophysical Observations ~ Dan J. Bower et al