Banded iron formation, Isua, Greenland. (IMAGE) University of Oxford Caption Study co-author Athena Eyster standing in front of a large exposure of banded iron formation, the iron rich deposit from which ancient magnetic field signals were extracted. Credit: Claire Nichols. Credit Claire Nichols. Usage Restrictions The image can be used for editorial purposes ONLY and MUST be credited. The image MUST NOT be sold on to third parties. 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.