TAP Colloquium- Rock 'n roll in the Solar system and beyond: outside-the-box thinking on planet and moon formation

Abstract: Planet formation begins with the collisional growth of small planetesimals accumulating into larger ones. Such growth occurs while planetesimals are embedded in a gaseous protoplanetary disc. However, small planetesimals experience collisions and gas drag that lead to their destruction on short time-scales, not allowing, or requiring fine-tuned conditions for the efficient growth of ̃meter-sized and larger objects.  I will discuss how the same problematic gas-drag which initially gave rise to the meter-size barrier can also serve to solve it, and as well as assist in other planetary growth problems. In particular, I will show that interstellar planetesimals like the recently discovered ones going through the Solar system could be gas-drag captured into protoplanetary disks and serve the seed for early efficient planetesimal growth. These can provide a novel "outside the box" scenario to alleviate the "meter-size" barrier or at least making it exponentially easy to solve. We will then change gears to discuss the origins of the peculiar contact binary discovered by New-Horizons at the edge of the Solar system (Ultima-Thule), and show how Lidov-Kozai - like processes operate in the Solar system. Finally, if time permits, I will suggest a new multiple-impact model for the origin of Earth-Moon (and other terrestrial moons/exomoons). Since the final stage of terrestrial planet formation involves many giant impacts, we suggest that the natural outcomes are the large-impact formation of many moons around the proto-Earth during its evolution. In particular, Earth-moon had had many older moon siblings, and itself might be the product of the mergers of several moons over time, rather than the product of a single giant impact.

Refreshments served at 3:15 pm in the Kuiper Atrium