Images of Io's Sodium Cloud

See allHide authors and affiliations

Science  03 Feb 1978:
Vol. 199, Issue 4328, pp. 531-533
DOI: 10.1126/science.199.4328.531


The first direct images of Io's sodium cloud are reported and analyzed. The observed cloud extends for more than 105 kilometers along Io's orbit and is a somewhat "banana-shaped" partial toroid. More sodium atoms precede Io than follow it. A model based on the escape of sodium from a specific localized area on Io provides a reasonable fit to the observed intensity distribution whereas isotropic escape does not.