Delivery of Organics


OBJECTIVE 3: HOW ARE ORGANICS IN PROTOPLANETARY DISKS DELIVERED TO HABITABLE ZONE PLANETS?

Team Lead: Fred Ciesla

The objective of our team is to understand how biocritical elements are delivered to habitable planets.  We will carry out a series of numerical investigations to understand how organics and volatiles are incorporated into planetary building blocks and then trace the dynamical evolution of these building blocks throughout the period of planetary assembly.  The results of such models will be compared to the ever growing exoplanet database, as we work to understand what conditions are necessary to produce the observed exoplanet systems, both in terms of their orbital architectures and atmospheric compositions.  In this way, we will catalog the possible paths that given planetary systems took during their early evolution in our Genesis Database, and make predictions about the properties of habitable zone planets throughout the galaxy.

 


Project 3.1: HOW WERE ORGANICS INCORPORATED INTO MINOR BODIES?

Lead: Krishna Muralidharan

Project 3.1 will provide a quantum chemical window into the nature, type and amount of organics that could be delivered to habitable planets. To achieve this we will work closely with Project 1.1, and study how organics and volatiles chemically bind to grain surfaces present in the planetary accretion disk. Molecular dynamics and density functional theory will be employed to catalog the binding energy of adsorption of a host of organic compounds as identified by Project 1.1, onto mineral grains. Simultaneously, the ability of surface mediated formation of complex organics will also be examined. The binding energy of the organic compounds will serve as the input for kinetic Monte Carlo techniques that will be used in tandem with the dynamic compound wavelet matrix method to assess and quantify the organics’ stability at conditions pertaining to the accretion disk. The success of this project will serve as an important step towards developing a multiscale atomic units to astronomical units model for predicting the inventory of organics that will be incorporated into planetesimals and ultimately habitable planets.


Project 3.2:  DISK-PLANET CONNECTION: THE GENESIS DATABASE

Lead: Fred Ciesla and David O’Brien

In Project 3.2, we will simulate the accretion of terrestrial planets in order to understand the amount of biocritical elements that would be delivered to habitable zone planets.  In tracking the growth of planets, we will track the provenances of the building blocks that each planet accretes in order to determine the volatile and organic budget of these bodies.

To do this, we will carry out a large number of N-body accretion simulations.  We will investigate how accretion occurs in the presence of a photoevaporating protoplanetary disk, accounting for planet-disk interactions and gas drag.  We will also explore a large parameter space, investigating how the final planetary system architecture and planetary properties are influenced by the planetesimal disk surface density and size.

Given the stochastic nature of planetary accretion, each realization of a protoplanetary disk will be modeled ~tens of times in order to provide statistically significant outcomes that will allow us to quantify the confidence of results.  Further, we will catalog each run in the Genesis Database, recording the initial conditions and evolutionary pathway each model system took to produce a final result.  Such outcomes will allow us to understand how different processes and conditions combine to yield the diversity of systems that we observe.


Project 3.3: GENESIS DATABASE VS OBSERVED PLANETARY ARCHITECTURES

Lead: Ilaria Pascucci

In Project 3.3 we will explore the statistical relationships between the properties of planetary systems, and develop a tool for linking the properties and formation histories of the planetary systems in the Genesis Database to the planetary systems in the galaxy. In doing so, we will test our models for planet formation and evaluate the probability that habitable planets are present around stars of various types.


Project 3.4: TOWARD DENSITIES AND ATMOSPHERIC COMPOSITION OF SUPER-EARTHS

Lead: Daniel Apai

In Project 3.4 we will expand our ongoing ACCESS exoplanet spectroscopy survey and – from Year 4 – include TESS-discovered super-earths, compiling the largest transmission spectral library of exoplanets, including 20 super-earths. We will compare the exoplanets’ dominant atmospheric components as a function of host star properties (composition and mass) and planet properties (mass, density, irradiation, orbital radius) to trends from the planet formation models and the Genesis database we developed (Projects 3.2 and 3.3).