Giant pumice raft on ancient Mars

摘要

A HUGE floating raft of volcanic rock called pumice may have drifted across an ancient Martian ocean and created one of the most mysterious features we can see on the planet's surface today. The Medusae Fossae Formation (MFF), found near Mars's equator, comprises about 5000 kilometres of rolling hills and mounds. Scientists have suggested that it was made of volcanic ash from the nearby Olympus Mons or Elysium Mons volcanoes.