Moon Undergoing Subsurface Sparking (image) NASA/Goddard Space Flight Center Caption This illustration shows a permanently shadowed region of the moon undergoing subsurface sparking (the 'lightning bolts'), which ejects vaporized material (the 'clouds') from the surface. Subsurface sparking occurs at a depth of about one millimeter. Image not to scale. Credit Andrew Jordan/UNH Usage Restrictions None 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.