Planetary Bombardment Model (VIDEO) Southwest Research Institute This video is under embargo. Please login to access this video. Caption A Southwest Research Institute-led team updated planetary bombardment models to understand how large impacts, such as the one illustrated here, may have affected oxygen levels in the Earth’s atmosphere in the Archean eon, 2.5 to 4 billion years ago. Credit SwRI/Simone Marchi Usage Restrictions Images/videos may be used by the media and the public for educational and informational purposes only License Original 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.