From The Woods Hole Oceanographic Institution
6.24.24
Freshly emplaced (since 2018) lava mounds (black with yellow hydrothermal mineral staining) at the crater floor of KSM (Jan 2023). ROV Jason prepares to insert a temperature senor into a newly formed hydrothermal vent (yellow stained area, bottom right) within the recently erupted lavas. (©Woods Hole Oceanographic Institution)
A new study led by team members at UC Santa Cruz have used a complex computer model to investigate how the influence of low gravity, as found on ocean worlds in our outer solar system, could influence flows of water and heat below their seafloors.
The work was conducted as part of a multi-institutional “Exploring Ocean Worlds” NASA program, led by Woods Hole Oceanographic Institution (WHOI) Senior Scientist Chris German. It has shed new light on the potential for seafloor hydrothermal venting —which hosts some of the most primitive life forms on Earth — to occur on other “Ocean World” moons orbiting giant planets in the outer Solar System.
ROV Jason’s manipulator arm using an Isobaric Gas-Tight (IGT) sampler to collect warm (~40°C) vent-fluids at the Kama’ehuakanaloa Seamount (KSM), January 2023. (©Woods Hole Oceanographic Institution)
Our solar system contains many “ocean worlds,” planets and moons that currently have, or have had in the past, a liquid ocean. Some of these ocean worlds may release enough heat internally to drive hydrothermal circulation – water that flows into the seafloor, circulates, and is warmed, and flows back out. On Earth, these flows can carry heat and chemicals, some of which are key to supporting lush seafloor ecosystems. These rock-heat-fluid systems were discovered on Earth’s seafloor in the 1970s, and many scientists think they may exist elsewhere in our solar system – this is a topic of great interest, especially because there is potential to support life. The research team at UC Santa Cruz, in collaboration with colleagues at the Blue Marble Space Institute of Science, WHOI, and Nantes Université, have published their new study in the Journal of Geophysical Research: Planets, showing how hydrothermal systems like those seen on Earth might differ under lower gravity conditions of other ocean worlds.
Many people have heard about high-temperature vents on Earth’s seafloor, sometimes called “black smokers,” where fluids heated above 300 °C (much hotter than the boiling point of water at sea level on Earth) jet into the ocean, depositing metal ores and helping to support exotic life. While these high-temperature systems are driven mainly by subseafloor volcanic activity, a much larger volume of fluid flows in and out of Earth’s seafloor at lower temperatures, driven mainly by “background” cooling of the planet.
“The flow of water through low-temperature venting is equivalent, in terms of the amount of water being discharged, to all of the rivers and streams on Earth, and is responsible for about a quarter of Earth’s heat loss,” said Andrew Fisher, study lead author and a distinguished professor of earth and planetary sciences (EPS) at UC Santa Cruz. “The entire volume of the ocean is pumped in and out of the seafloor about every half-million years.”
“Many previous studies of hydrothermal circulation on Europa and Enceladus (moons of Jupiter and Saturn) have considered higher temperature fluids, and cartoons and other drawings often illustrate systems on their seafloors that look like black smokers on Earth,” explained Donna Blackman, an EPS researcher at UC Santa Cruz and third author on the new paper. “Lower temperature flows are at least as likely to occur, if not more likely.”
A Temperature sensor in shimmering warm vent fluids (~30°C) emanating from recently erupted (black) lavas. Yellow orange staining is due to hydrothermal mineralization (iron oxide) generated as a by-product of microbial life fueled by the warm fluids. ©Woods Hole Oceanographic Institution
Kristin Dickerson, the paper’s second author and a Ph.D. candidate in EPS at UC Santa Cruz, explained the basis for the study, “We looked at a seawater circulation system beneath Earth’s seafloor that has been studied for years. It was discovered deep in the northwestern Pacific Ocean, where cool bottom water flows in through one seamount (an extinct volcano), travels for 50 km, then flows out through another seamount.” This water gathers heat as it flows and comes out warmer than when it flowed in, and with very different chemistry. The researchers used a computer model that was developed for that Earth system, changing the value of gravity, and examining how flows would vary under a wide range of conditions (like different amounts of heating, rock properties, fluid circulation depth).
The flow from one seamount to another is driven by buoyancy, because water gets less dense as it warms, and more dense as it cools. Differences in density create differences in fluid pressure in the rock, and the system is sustained by the flows themselves. “We call it a hydrothermal siphon,” said Fisher, “and it can run as long as there is a supply of heat and rock properties continue to allow circulation.” Some ocean worlds are heated by large tides, which can generate heat as an ocean world is flexed during an eccentric orbit around a giant planet.
The new paper shows that, when gravity is lower than on Earth, there is a smaller buoyancy force driving flow in and out of the seafloor – this tends to slow circulation of water and remove heat. At the same time, less buoyancy when gravity is lower also results in less secondary mixing below the seafloor, a process that tends to use up energy and so reduce the flow between outcrops.
One exciting result from simulations featured in the new paper is that, under very low gravity (like that found on the seafloor of Enceladus, a small moon of Saturn), circulation can continue with low to moderate temperatures for millions or billions of years – i.e. throughout the life of the Solar System. This could help to explain how small ocean worlds, with gravity much lower than on Earth, can have long-lived fluid circulation systems below their seafloors: the low efficiency of heat extraction could lead to considerable longevity. In addition, some simulations resulted in vent fluid temperatures up to 150 °C, just above the upper limits to life on Earth, despite relatively shallow circulation below the seafloor. Overall, these simulations show that low gravity significantly changes temperatures and flow rates, and therefore likely impacts the chemistry of discharging fluids compared to what would be found on Earth.
Planetary scientists are looking to observations from satellite missions to help determine what kinds of conditions are present or possible on ocean worlds. The author team for the new paper will be attending the launch of the Europa Clipper spacecraft at Cape Canaveral, FL later this fall, along with colleagues collaborating on the Exploring Ocean Worlds project.
According to WHOI’s German, who is also co-author on the paper, “A significant outcome from this study is that it suggests that low temperature (not too hot for life) hydrothermal systems could have been sustained on Ocean Worlds beyond Earth over timescales much longer than it took for similar life to first take hold on Earth. Thus, Ocean Worlds in the outer solar system could also be habitable and, perhaps, host life.”
See the full article here .
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Mission Statement
The Woods Hole Oceanographic Institution is dedicated to advancing knowledge of the ocean and its connection with the Earth system through a sustained commitment to excellence in science, engineering, and education, and to the application of this knowledge to problems facing society.
Vision & Mission
The ocean is a defining feature of our planet and crucial to life on Earth, yet it remains one of the planet’s last unexplored frontiers. For this reason, WHOI scientists and engineers are committed to understanding all facets of the ocean as well as its complex connections with Earth’s atmosphere, land, ice, seafloor, and life—including humanity. This is essential not only to advance knowledge about our planet, but also to ensure society’s long-term welfare and to help guide human stewardship of the environment. WHOI researchers are also dedicated to training future generations of ocean science leaders, to providing unbiased information that informs public policy and decision-making, and to expanding public awareness about the importance of the global ocean and its resources.
The Institution is organized into six departments, the Cooperative Institute for Climate and Ocean Research, and a marine policy center. Its shore-based facilities are located in the village of Woods Hole, Massachusetts and a mile and a half away on the Quissett Campus. The bulk of the Institution’s funding comes from grants and contracts from the National Science Foundation and other government agencies, augmented by foundations and private donations.
WHOI scientists, engineers, and students collaborate to develop theories, test ideas, build seagoing instruments, and collect data in diverse marine environments. Ships operated by WHOI carry research scientists throughout the world’s oceans. The WHOI fleet includes two large research vessels ( R/V Atlantis and R/V Neil Armstrong); the coastal craft Tioga; small research craft such as the dive-operation work boat Echo; the deep-diving human-occupied submersible Alvin; the tethered, remotely operated vehicle Jason/Medea; and autonomous underwater vehicles such as the REMUS and SeaBED.
WHOI offers graduate and post-doctoral studies in marine science. There are several fellowship and training programs, and graduate degrees are awarded through a joint program with the Massachusetts Institute of Technology. WHOI is accredited by the New England Association of Schools and Colleges . WHOI also offers public outreach programs and informal education through its Exhibit Center and summer tours. The Institution has a volunteer program and a membership program, WHOI Associate.
On October 1, 2020, Peter B. de Menocal became the institution’s eleventh president and director.
History
In 1927, a National Academy of Sciences committee concluded that it was time to “consider the share of the United States of America in a worldwide program of oceanographic research.” The committee’s recommendation for establishing a permanent independent research laboratory on the East Coast to “prosecute oceanography in all its branches” led to the founding in 1930 of the Woods Hole Oceanographic Institution.
A $2.5 million grant from the Rockefeller Foundation supported the summer work of a dozen scientists, construction of a laboratory building and commissioning of a research vessel, the 142-foot (43 m) ketch R/V Atlantis, whose profile still forms the Institution’s logo.
WHOI grew substantially to support significant defense-related research during World War II, and later began a steady growth in staff, research fleet, and scientific stature. From 1950 to 1956, the director was Dr. Edward “Iceberg” Smith, an Arctic explorer, oceanographer and retired Coast Guard rear admiral.
In 1977 the institution appointed the influential oceanographer John Steele as director, and he served until his retirement in 1989.
On 1 September 1985, a joint French-American expedition led by Jean-Louis Michel of IFREMER and Robert Ballard of the Woods Hole Oceanographic Institution identified the location of the wreck of the RMS Titanic which sank off the coast of Newfoundland 15 April 1912.
On 3 April 2011, within a week of resuming of the search operation for Air France Flight 447, a team led by WHOI, operating full ocean depth autonomous underwater vehicles (AUVs) owned by the Waitt Institute discovered, by means of sidescan sonar, a large portion of debris field from flight AF447.
In March 2017 the institution effected an open-access policy to make its research publicly accessible online.
The Institution has maintained a long and controversial business collaboration with the treasure hunter company Odyssey Marine. Likewise, WHOI has participated in the location of the San José galleon in Colombia for the commercial exploitation of the shipwreck by the Government of President Santos and a private company.
In 2019, iDefense reported that China’s hackers had launched cyberattacks on dozens of academic institutions in an attempt to gain information on technology being developed for the United States Navy. Some of the targets included the Woods Hole Oceanographic Institution. The attacks have been underway since at least April 2017.
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