sentences:  Scientists suggested that the lake could possess a unique habitat for ancient bacteria with an isolated microbial gene pool containing characteristics developed perhaps 500,000 years ago.In January 2011, the head of the Russian Antarctic Expedition, Valery Lukin, announced that his team had only of ice left to drill in order to reach the water.The researchers then switched to a new thermal drill head with a "clean" silicone oil fluid to drill the rest of the way.