RT Journal Article SR Electronic T1 Snowball Earth Has Melted Back To a Profound Wintry Mix JF Science JO Science FD American Association for the Advancement of Science SP 1186 OP 1186 DO 10.1126/science.327.5970.1186 VO 327 IS 5970 A1 Kerr, Richard A. YR 2010 UL http://science.sciencemag.org/content/327/5970/1186.abstract