Scientists have discovered signs of life in mud samples extracted from the bottom of a sub-glacial lake in Antarctica. 
The researchers from the British Antarctic Survey uncovered microbes that date back nearly 100,000 years, along with organisms that were previously unknown to science, the team said in a statement detailing the research. 
To recover the samples, the scientists drilled though an ice sheet covering Lake Hodgson on the Antarctic Peninsula. The lake currently has a covering of ice about 10 to 13 feet thick. But more than 100,000 years ago -- during the last Ice Age -- the lake was covered with ice more than 1,300 feet thick. Rising global temperatures have greatly contributed to the thinning of the ice over Lake Hodgson. 
The researchers drilled almost 305 feet deep into the lake to reach its bottom, employing "clean core" drilling to avoid any contamination of the surrounding area. This drilling style uses sterilized equipment in order to protect the team's samples from contamination concerns, Forbes reports.
The upper few centimeters of the core contained recent organisms. But as the scientists continued drilling, they found fossilized fragments of DNA belonging to numerous microbes that appeared to have adapted to the extreme conditions over the millennia. The team found several types of bacterial species known to science in the lakes. But they also concluded that 23 percent of the organisms present in the samples could only be labeled as “unidentified bacterium.”
“The subglacial units in the Lake Hodgson sediment cores have demonstrated that a high diversity of life at relatively low biomass is present in Antarctic subglacial lake sediments,” according to researchers in their paper published in the journal Diversity.
Pearce says additional studies will continue to determine more information about the life forms and how they succesfully thrive in the extreme conditions of the Arctic. This information could also help scientists better understand the possibility and limits of life on other planets with similarly extreme environments. 
“The fact these organisms have survived in such a unique environment could mean they have developed in unique ways which could lead to exciting discoveries for us,” said lead researcher David Pearce in a statement. “This is the early stage and we now need to do more work to further investigate these life forms.”