Cosmic Dust Grain (IMAGE) NASA/Goddard Space Flight Center Caption A sample of cosmic dust collected from Earth's stratosphere. The grain is about five micrometers across - approximately the size of a human red blood cell. Credit NASA's Johnson Space Center/Cosmic Dust Collection Program Usage Restrictions None 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.