The First Billion Years

The First Four Billion Years

Life: the first two billion years.

Microfossils, stromatolites, preserved lipids and biologically informative isotopic ratios provide a substantial record of bacterial diversity and biogeochemical cycles in Proterozoic (2500-541 Ma) oceans that can be interpreted, at least broadly, in terms of present-day organisms and metabolic processes. Archean (more than 2500 Ma) sedimentary rocks add at least a billion years to the recorded...

The first billion years: new insights from geochemistry

Prologue: (V)ast globes. . . after reaching the last stages of ebullition, were coveredwith scoriae like bubbling foam. And the crust which covered the molten matter of the globe and which hardened from the fused condition would be like scoria, as happens with metals in the furnace. If then the great framework of the earth, the exposed rocks, the imperishable silicates, are almost entirely vitr...

SCORCH I: The Galaxy-Halo Connection in the First Billion Years

SCORCH (Simulations and Constructions of the Reionization of Cosmic Hydrogen) is a new project to study the Epoch of Reionization (EoR). In this first paper, we probe the connection between observed high-redshift galaxies and simulated dark matter halos to better understand the primary source of ionizing radiation. High-resolution N-body simulations are run to quantify the abundance of dark mat...

A sawtooth-like timeline for the first billion years of lunar bombardment

We revisit the early evolution of the Moon’s bombardment. Our work combines modeling (based on plausible projectile sources and their dynamical decay rates) with constraints from the lunar crater record, radiometric ages of the youngest lunar basins, and the abundance of highly siderophile elements in the lunar crust and mantle. We deduce that the evolution of the impact flux did not narrow imp...