Scientists have returned to learn more about the marine life living at extreme depths in the Cayman Trough.
Throughout this month, a team of oceanographers and astrobiologists will explore hydrothermal vents in the depths of the Caribbean Sea. The vent sites were discovered during earlier expeditions in 2009 and 2010.
Researchers are using the hybrid underwater robotic vehicle Nereus to explore the Mid-Cayman Rise, an ultra-slow moving centre between the Cayman Islands and Jamaica*, where two plates gradually move apart and upwelling magma creates new crust, and the adjacent Cayman Trough, also known as the Cayman Trench.
Led by Chris German from the Woods Hole Oceanographic Institution, the expedition includes international scientists from Woods Hole, British Geological Survey, NASA Jet Propulsion Lab and the Marine Biological Laboratory.
“By exploring this extreme and previously uninvestigated section of the Earth’s deep seafloor, this research seeks to extend our understanding of the limits (in terms of extreme environments) to which life can exist on Earth, to understand how geologic processes might generate the prebiotic materials believed to have been an essential precursor to life on Earth, and to help prepare for future efforts to explore for life on other planets,” wrote Mr. German on the expedition’s website, on which he is maintaining a blog.
Among the team is astrobiologist Max Coleman, who searches for signs of life outside the Earth. He has joined the expedition because the Cayman Trough location is believed to be the closest thing Earth has to the deep hydrothermal vents thought to exist on Europa, a moon of Jupiter. While previous explorations of the vents allowed the scientists to develop protocols for searching for hydrothermal vents on Europa, the next phase of this part of the expedition focuses on understanding the possibilities of finding life associated with these kinds of vents.
The crew is aboard the research vessel R/V Falkor, which set sail from St. Petersburg, Florida, on 30 May. The ship was originally scheduled to stop off in Grand Cayman this weekend to before setting off again for the Mid-Cayman Rise on 19 June, but Mr. German said the plan now is to go to Jamaica instead for its port call. The expedition is due to be completed by 30 June.
From water-column analyses, scientists say the Mid-Cayman Rise has at least four vent sites, each in a distinct geologic setting. So far, only two – Von Damm and Piccard – have been located. The other two, Europa and Walsh, have yet to be traced to their source.
“The mission is two-fold,” Mr. German told the Caymanian Compass in an email sent from the ship Tuesday. “This leg we have been exploring for the two “missing” vent-fields. We tracked one to within 1 kilometre but were stymied with making any better progress so we have moved to the other site - Europa - and will be spending the rest of this week tracking that down.
“Next leg, we will be converting our free-swimming vehicle into a remotely piloted ROV and using that to collect samples and send video feeds live from the seabed to the internet so you can follow along with us,” he said, adding that the planned dates for the live feeds are 20-29 June.
An earlier expedition collected samples of blind vent shrimp, echinoderms, tubeworms, lobsters, sponges, corals and anemones, some of which have only been found in and around the vents.
At the Von Damm site, about 1.4 miles below the surface, a new species of shrimp was discovered, as well as two species of tubeworm during earlier explorations. Thirty miles away and three miles deep, the Piccard site has three active centres – the Beebe Vents, Beebe Wood and Beebe Sea sites. The Beebe Vents is an active black smoker, the deepest vent yet discovered and also the hottest, reaching temperatures greater than 400 degrees Celsius.
Although no tube worms have been found at this site, shrimp of the same species as at Von Damm were discovered, but were much smaller, suggesting a distinct and isolated population.
During the current expedition, the researchers are doing conductivity, temperature and depth of seawater casts, high resolution vent site mapping, chemical and physical data collection, interactive research, observation and sampling of associated biological communities, and satellite teleoperations with shore-side scientists.
The Nereus, built and operated by Woods Hole Oceanographic Institution engineers, can swim freely as an autonomous underwater vehicle to survey and map large areas of the sea floor and sense for chemical anomalies in the water column. When it finds something of interest to the scientists on board the ship miles above, it can be transformed into a remotely operated vehicle tethered to the ship via a microthin, fibre-optic cable.
Through this cable, the robot can transmit high-quality, real-time video images back to the ship and follow commands to collect samples or conduct experiments with a manipulator arm.
Editor's note: This story has been corrected from the original.