Exploring Oceanfloor Hydrothermal Vents- Geysers that Entice Astrobiologists

Hydrothermal vents on the seafloors are thought to be possible sites for the origin of life on Earth. A hydrothermal vent is a geyser on the seafloor. A team of scientists from Woods Hole Oceanographic Institution and NASA Astrobiology Institute, explored the 68-mile-long Mid-Cayman rise deep beneath the surface of the Caribbean and discovered the deepest known hydrothermal vent in the world.

Hydrothermal vents continuously gushes super-hot, mineral-rich water. Though the gushing water from hydrothermal vents may be as hot as 500 deg Celsius, this super-heated water does not boil due the pressure from the ocean water above. These geysers deep under water, on the sparsely populated seafloor, supports a diverse community of organisms. It is believed that Jupiter's moon, Europa, is composed of rock like that on Earth but is covered by a deep ocean topped with a shell of ice and life in the liquid ocean may be survived by similar mechanisms as seen near the hyrdrothermal vents.

Using an autonomous, submersible robotic vehicle NASA and Woods Hole scientists explored three different sites on the ocean floor and obtained valuable information on the life forms survived by these geysers. This study was published in a recent issue of PNAS.

The team performed chemical and microbiological sampling of the vent area. They identified the site of the deepest hydrothermal vent so far discovered at approximately 5 km. In a surprisingly short distance they identified three vent types hosted at different depths in different rock types. It is expected that abiotic organic matter from these vents form part of the base of a food chain for the local ecosystem, which is such a great distance from photosynthetic primary production. When the ecosystem on the surface of the earth is sustained by solar energy, the ecosystem near the hydrothermal vent is likely to be sustained by chemicals in the hydrothermal fluid.

With the acquired DNA and other information, the authors speculate that their new results will provide insight into the evolution and dispersion of the biological organisms at the deep seafloor vent.

The expedition in the Caribbean south of Grand Cayman Island, identified prospective vent targets in the preliminary simulation of what will be needed to explore under the ice on Europa. Mars and Europa, give hints that they might harbor liquid water beneath their surfaces. Also, NASA's Cassini spacecraft discovered a giant plume of water gushing from cracks in the surface over Saturn's icy moon Enceladus, indicating that there was a reservoir of water beneath the ice. With continuing efforts to identify extraterrestrial life forms and speculation on the mechanism of origin and maintenance of such life forms, results from studies such as this may be critical.

The studies published in the issue of PNAS report evidence for previously unknown, diverse, and very deep hydrothermal vents along the 110 km long, ultraslow spreading Mid-Cayman Rise.

References:

PNAS publication

Europas Hidden Ice Chemistry

Hydrothermal vents, University of Delaware