The Lost City Hydrothermal Field, often referred to simply as Lost City, is an area of marine alkaline hydrothermal vents located on the Atlantis Massif at the intersection between the Mid-Atlantic Ridge and the Atlantis Transform Fault, in the Atlantic Ocean. It is a long-lived site of active and inactive ultramafic-hosted serpentinization, abiotically producing many simple molecules such as methane and hydrogen which are fundamental to microbial life. As such it has generated scientific interest as a prime location for investigating the origin of life on Earth and other planets similar to it.
Expedition history
The Lost City was first identified on December 4, 2000, using DSV Alvin and ROV ArgoII on cruise AT03-60 of the RV Atlantis. The cruise lasted 34 days, during which photographs and vent chimney samples were taken. The discovery of the Lost City prompted the National Science Foundation to fund a second, 32-day voyage (AT07-34) to the site in 2003 in order to use Alvin and the autonomous vehicle ABE with a greater emphasis on scientific sampling and creating a high-resolution bathymetric map of the vent field. ABE would participate in a combined 17 dive expeditions including follow-up visits, creating a bathymetry profile for 3.3 square kilometres (1.3 sq mi) of the massif. The first visit by the Integrated Ocean Drilling Program took place with Expedition 304 in late 2004, when a series of holes were drilled into the Atlantis Massif to collect large cores of rock from the site. Expedition 305 followed suit in early 2005, and 340T in 2012. In July 2005, Lost City was explored for nine days by Hercules and Argus on the National Oceanic and Atmospheric Administration vessel Ronald H. Brown, with video streamed live to the University of Washington in Seattle. Lost City was also explored on cruise 50 of the Akademik Mstislav Keldysh, which had a greater emphasis on exploring downslope south of the vent field. The RV Knorr sailed to the Atlantis Massif in May that year for hydroacoustic measurements of potential seismic activity. Furthermore, the French EXOMAR cruise on the vessel L'Atalante was conducted in July and August 2005 to study extremophile biodiversity in deep-ocean environments. 2015 saw a visit from the International Ocean Discovery Program Expedition 357, which emphasized drilling on the Atlantis Massif to explore off-axis circulation. A series of boreholes were left behind after cores from nine different sites were taken, which were sampled by Niskin bottles. Borehole plugs were installed on two sites to allow future endeavors to sample borehole fluids.
In July and August 2018, the French TRANSECT cruise was conducted on L'Atalante utilizing the ROV VICTOR to collect a variety of measurements and samples. The following month, American cruise AT42-01, nicknamed Return to the Lost City, was undertaken to revisit the vent field after many years, featuring many members of the original discovery team in 2000. Photographs, ambient gases, cells for cultures, rock, vent fluid, and ambient seawater samples were collected using the ROV Jason II and a CTD Niskin rosette. The mission's key objectives were to collect biological and geochemical samples for researching sources of energy for microbial life. They also followed up on the 2015 borehole expedition by attempting to sample from the drilled holes for access to residual fluids. In March 2023, the first cruise of the RV Falkor Too was undertaken to deploy a new in-situ methane sensor to search for hydrothermal activity similar to that of Lost City along the Mid-Atlantic Ridge. ROV dives were live-streamed to the Schmidt Ocean Institute's website. The cruise concluded on April 11, having identified new black-smoker vents.
Geography
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