Miles below the ocean’s surface lies one of the most inhospitable habitats on the planet. Deep inside subterranean cracks, where seawater seeps through the perpetually hot rock in Earth’s crust, there’s a surprisingly rich ecosystem of microorganisms. Scientists have long been eager to study these creatures—along with the larger geological setting—but drilling holes in the seafloor large enough to drop instruments down floods the habitat with cold water and kills off the fauna. That’s where a type of rig called a Circulation Obviation Retrofit Kit, or CORK, comes in. Researchers install these observatories in boreholes, with a two-story-tall wellhead that forms a seal to protect the environment below—and a half mile or so of instrumentation. Here’s how.

• RESEARCH SHIP
  Scientists on research vessels use sonar to help determine where to place the CORKs. They later deliver the components and drilling equipment. After installation, they visit periodically to retrieve samples and data and to service the observatory.
• BOREHOLE
  Holes are drilled a kilometer down into the seafloor. The borehole is dug in stages, with concentric steel casings inserted to stabilize it. When the casings are in place and sealed with cement and rubber, researchers lower the CORK structure to seal off the hole.
• INSTRUMENTS
  Sensors and sampling devices are positioned throughout the CORK’s shaft to measure water pressure and temperature and collect samples.
• ROV PLATFORM
  The CORK can be left in place for 10 years. The observatory is serviced by remotely operated vehicles, which are lowered to its 13-foot-wide platform.
• LIFE-FORMS
  The initial drilling inevitably upsets the ecosystem, but it returns to its natural state in a few years. Researchers recently opened a four-year-old CORK and discovered a colony of unknown microbes that might have been impossible to find any other way.

Illustration: James Provost