Earth-Moon (IMAGE) Southwest Research Institute Caption Scientists at Southwest Research Institute combined dynamical, thermal, and chemical Moon formation models to explain key differences between the composition of lunar rocks and the Earth's. The Moon's lack of easily vaporized elements provides evidence about how the Earth-Moon system formed 4.5 billion years ago. Credit Image Courtesy of NASA/Southwest Research Institute Usage Restrictions Image Courtesy of NASA/Southwest Research In License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.