Fill in the blanks with the appropriate words:

The accidental ____(1)____of marine organisms on a boulder on the sea floor beneath 900 metres (3,000ft) of Antarctic ice shelf has led scientists to rethink the limits of life on Earth. Researchers stumbled on the life-bearing rock after sinking a borehole through nearly a kilometre of the Filchner-Ronne ice shelf on the south-eastern Weddell Sea to ____(2)____ a sediment core from the seabed. While the boulder ____(3)____ their chances of obtaining the core, footage from a video camera sent down the hole captured the first images of organisms ____(4)____ to a rock far beneath an ice shelf. Ice shelves form when frozen water from the continent’s interior flows to the coast and floats on to the surrounding sea. As the ice flows over the land, it can pick up boulders that become ____(5)____ in the base of the ice shelf before dropping out on to the sea floor.