Lost City Hydrothermal Field

The Lost City Vent Field or Lost City is a series of alkaline hydrothermal vents located on the Atlantis Massif at the intersection between the Mid Atlantic Ridge and the Atlantis Transform Fault. It is a long-lived site of active and inactive ultramafic-hosted serpentinization, abiotically producing many molecules such as methane and hydrogen that are fundamental to microbial life. It is a prime location for investigating the origin of life on Earth and other planets similar to it.Olivine(Fe,Mg)2SiO4 + Watern·H2O + Carbon dioxideCO2 → SerpentineMg3Si2O5(OH)4 + MagnetiteFe3O4 + MethaneCH4    (Methanogenesis)Fayalite (Olivine)3 Fe2SiO4 + water2 H2O → Magnetite2 Fe3O4 + Silica (aqueous)3 SiO2 + Hydrogen2 H2    (Hydrogenesis)A white carbonate spire in the Lost City vent field.Hercules maneuvers around rocky spires.View of a flange from the underbelly of an ROV.Warm vent fluids coming from the pristine interior of a broken flange.Iron plates dropped on the seafloor as ballast.A 9.1 metres (30 ft) chimney at Lost City. The Lost City Vent Field or Lost City is a series of alkaline hydrothermal vents located on the Atlantis Massif at the intersection between the Mid Atlantic Ridge and the Atlantis Transform Fault. It is a long-lived site of active and inactive ultramafic-hosted serpentinization, abiotically producing many molecules such as methane and hydrogen that are fundamental to microbial life. It is a prime location for investigating the origin of life on Earth and other planets similar to it. The Lost City was identified on the 4th of December, 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 to use Alvin and the autonomous vehicle ABE with a greater emphasis on scientific sampling and creating a high-resolution bathymetric map of the field. ABE would do a combined 17 dive expeditions including following 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 in late 2004 with Expedition 304, when a series of holes were drilled into the Atlantis Massif to collect large cores of rock from the site. Expeditions 305 followed suit in early 2005, and 340T in 2012. In July 2005, Lost City was explored for 9 days by Hercules and Argus on the NOAA vessel the 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 hydoacoustic measurements of potential seismic activity. 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 9 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 September 2018, cruise AT42-01 nicknamed 'Return to the Lost City' was undertaken to revisit the vent field, 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. Lost City is located on the seafloor mountain Atlantis Massif approximately the size of Mount Rainier. The site is described as a long-lived vent field, estimated to be older than 120,000 years by carbon dating the oldest chimney deposits of the field. However, this is significantly younger than the age of the Atlantis Massif itself, which may be as old as 2 million years. Lost City is located on a shelf approximately 70 m (70 metres (230 ft)) below the massif summit at a depth of around 750–900 m (2,460–2,950 ft), with an approximate area of 500 square metres (5,400 sq ft). The massif itself may originate in a similar manner to many other ocean core complexes. Lost City is a location dominated by steep cliffs to the south, chimneys, and mounds of carbonate material deposited from chimneys that collapse as they age. Breccia, gabbros, and peridotites are dominating rock types as one maneuvers away from the field, which are prone to mass-wasting as bathymetry steepens. Mass-wasting events of the past are evident by bountiful scarps on the slope of the massif. Rubble tends to accumulate at areas no steeper than 60 degrees bounding the field, and can undergo lithification depending on how far it is located from Lost City.