WeknowmoreaboutthesurfaceoftheplanetMarsthanweknowabout...
問題詳情：WeknowmoreaboutthesurfaceoftheplanetMarsthanweknowaboutwhatisatthebottomofEarth'soceans.Untilrecently,scientistshadmappedonlyabout20percentoftheseafloor.Butourknowledgeofthedeepseasischanging...