Scientists drilling ice cores in Greenland have recovered what appear to be plant remains from nearly 3km (two miles) below the surface.
Some of the material looks like pine needles or blades of grass
Team members said reddish clumps of material, found in the muddy ice in the cores, contain what look like pine needles or blades of grass.
If confirmed, it will be the first organic material to be recovered from a deep ice core drilling project.
Scientists think the material could be several million years old.
The suspected plant material was recovered between the ice sheet and the bedrock at a drilling site in central Greenland, by a team belonging to the North Greenland Ice Core Project (NGrip).
"Several of the pieces look very much like blades of grass or pine needles," said Professor James White, a principal investigator on the NGrip project from the University of Colorado at Boulder.
They may date to before the ice sheet covered the island during the last Ice Age. Samples of the material will now be sent off to several laboratories for analysis.
"There is a big possibility that this material is several million years old, from a time when trees covered Greenland," said Professor Dorthe Dahl-Jensen, of the University of Copenhagen's Niels Bohr Institute.
She added that, if the remains are indeed organic, their presence would suggest that the Greenland ice sheet formed very fast.
In summer 2003, the drilling team reached the bedrock at a depth of 3,085m. Trapped gas in the cores could help researchers determine how the area's climate varied year on year over the past 123,000 years.
The cores were recovered from about 3km beneath the ice surface
After reaching the bedrock, reddish water flooded the lowest 45m of the bore hole. At this site, the ice sheet is melting at the bottom due to high geothermal heat.
The water is running in channels in and under the ice, and is part of a sub-glacial system that may have been isolated from the surface for several million years.
This year, the researchers returned to drill down into the reddish refrozen water and retrieved the ice cores with the suspected organic material. These ice cores also have a very high content of trapped gas.
Some of the project members even think there is a possibility exotic life forms might survive in this ice.
The cores are cylinders of ice 10cm (four inches) in diameter that have been drilled in the ice and brought to the surface in 3.5m (11.5ft) lengths. The researchers work to recover the cores in subsurface trenches where temperatures frequently fall to -30C (-22F).
Each yearly record of ice can reveal past temperatures and precipitation levels, the content of ancient atmospheres and even evidence for the timing, direction and magnitude of distant storms, fires and volcanic eruptions.
NGrip is an international project with members from the US, Japan and Europe.