The multi-institutional Center for Lunar Origin and Evolution (CLOE) explores how our planetary system formed and evolved and how this record bears on both the geophysical/geochemical make-up of the Moon and the lunar cratering record. CLOE goals are (i) to use the Moon to tell us about the origin and history of the rest of the solar system, and (ii) to use the solar system to inform us on how the Moon formed and evolved.
CLOE’s scientific research comprises three main scientific themes:
Theme 1, “Formation of the Moon”: CLOE is modeling the evolution of the moon from its origin in a giant impact on Earth through to the end of the Moon’s accumulation. A first step in understanding the origin of the Moon within this paradigm is to develop computer simulations of collisions between planet-sized objects.
Theme 2, “Observational Constraints on the Bombardment History of the Moon”: CLOE is employing inventive techniques to deduce new physical constraints on the lunar impact rate over the last 4.5 billion years. Researchers have counted craters on a wide variety of lunar terrains and analyzed terrestrial and lunar samples that are sensitive to, and have information on, the record of ancient impacts on the Earth-Moon system. CLOE’s goal is to use lunar and meteoritic samples to establish an early lunar bombardment chronology.
Theme 2a: Thermochronometry and the Bombardment History of the Moon. CLOE graduate student and postdoc research followed the following themes: (i) Impact processes in silicate crusts (Earth, Moon, asteroids); (ii) Bombardment record of the early Earth; and (iii) The thermal evolution of planetary surfaces from impacts and radionuclides. Highlights of our thermal-chemical studies of impacts include lunar samples and the asteroid Vesta.
Theme 2b: Relative Lunar Crater Chronology. Researchers have analyzed the Moon’s cratering impact record to better understand its bombardment history, from the later portions of the Late Heavy Bombardment until the present. The team has compiled craters counts of Imbrium and Birkhoff basins from newly digitized Lunar Orbiter images, generating a new dataset of smaller craters within lunar basins.
Theme 3: Determining Lunar Impact Rates. Once the surface of the Moon solidified, it mainly has been shaped by impacts. As a result, the surface of the Moon stands as a witness to the late stages of planet formation and the evolution of the planetary system as a whole. The goal of Theme 3, therefore, is to construct the most complete theoretical models of the impact history on the Moon based on new dynamical models of the Solar System.
Theme 3a. Understanding Planet Formation In Order to Constrain the Moon’s Earliest History. CLOE has constructed the most advanced code to date to study the end-to-end process of planet formation, referred to as the Lagrangian Integrator for Planetary Accretion and Dynamics (LIPAD). LIPAD’s greatest strength is that it can accurately model the wholesale redistribution of planetesimals due to gravitational interaction with embryos, which has recently been shown to significantly affect the growth rate of planetary embryos. Initial LIPAD work shows significant differences with previous works.
Theme 3b. Understanding Giant Planets Migration and the Late Heavy Bombardment. The Late Heavy Bombardment (LHB) is an epoch that is believed to have ended ~3.8 Ga with the formation of Orientale basin. The Nice model argues the LHB was set into motion by the rearrangement of the outer giant planets. The Nice model is compelling because it quantitatively explains the orbits of the jovian planets and the capture of comets into several different small body reservoirs in the outer solar system (e.g., Trojans of Jupiter/Neptune, the Kuiper belt/scattered disk, the irregular satellites). These accomplishments are unique among models of outer solar system formation.
Read the team summary report for years 1-3