[DLS] Seth Jacobson (MSU)

“The first planetesimals came in twos and threes: gravitational collapse products in the inner solar system”

An intermediate step in the core accretion theory of planet formation is the creation of the first gravitationally bound solid objects within the planetary system. Rather than their slow accumulation through pairwise collision events, these first planetesimals likely formed through relatively sudden gravitational collapse events from swirling clouds of astrophysical pebbles, which are mm- to cm-sized aggregates of micron-sized dust and ice grains held together by weak surface forces. This gravitational collapse process shortcuts growth barriers and simulations of this process produce planetesimal systems that resemble relict planetesimals leftover in the solar system including their sizes, shapes, and spin states. Furthermore, simulated planetesimals are rarely formed alone but rather birthed in large groups and with many bound subsystems including binaries, ternaries, and even higher multiplicity systems. Planetesimal formation is a fast dramatic process with long-term consequences for how the solar system appears today.

EAPS Department Lecture Series —

Weekly talks aimed to bring together the entire EAPS community, given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. Runs concurrently with class 12.S501.

Contact: eapsinfo@mit.edu