A dry planet and one with a thick atmosphere close together seems to be very weird. How about smashing one with a huge impactor?
How to form clumps in the intermediate ranges of massive protoplanetary disks? Could these later be planets?
A model that needs fewest parameters to explain a scenario is favourable. The fact that mm-size dust grains (chondrules) are present in the entire solar system brings rise to the question, whether all bigger solid objects are a collection of chondrules.
Last year, an image was released that took our breath away. Exquisite rings carved in a disk of material around a nearby star. Now, astronomers want to know if forming planets are responsible, and why the image might look different from the cartoon in your textbook.
Planets are ubiquitous in the Milky Way. Therefore, building them must be straightforward, right? Not at all!
Earth’s atmosphere is about 100 times less massive than Venus’ atmosphere. This gave rise to the idea that Earth had a more massive atmosphere, which got then depleted by impacts. This Astrobite discusses what would have been the optimal impactor size.