External Sources of Heavy Metals for Tool Use by Developing Intelligences on Exoplanet Ocean Worlds

Abstract

We model the influx of metals and other compounds into the atmospheres of giant ocean worlds around other stars. There are over 4800 known exoplanets (planets outside of our solar system), 6% of which account for ocean world planets with oceans of liquid water that contain more than 1% of their mass in the form of water. These oceans have depths that range from 100 km on planetary moons to 12,000 km on planets that are seven times the mass of the Earth (e.g., the exoplanet GJ 1214b). Quantifying the input of metals into ocean world atmospheres has implications for the chemistry of the early oceans soon after their formation and thus on the prebiotic environment for the formation of life. It also has implications for the development of intelligent entities because this influx of metals will be a source of materials from which to make tools, eventually technology. For a case study, we consider the ocean world GJ 1214b, which is 6.3 times Earth mass, and 2.8 times Earth's radius. We calculate the influx of asteroidal and cometary material by assuming the nominal flux equals that at the Earth. We scale that flux to the size of GJ 1214b, including the effect of gravitational focusing. We find that the influx is 96 kg/m^2/yr early in the history of this planet, decreasing to about .96 mg/m^2/yr now. The next step to understand the metal evolution of GJ 1214b is to observe the system's asteroid belt and develop models of the sedimentation and chemistry of metals inside the planet.