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The Table S1-S6 are curated breakout notes from the NSF-funded FUTURE 2024 Workshop (March 26-28, 2024).  During the workshop, the first day of discussions focused on “Critical science questions that require seafloor sampling,” where participants: (I) defined the important sample types/sampling environment of their research; (II) assessed how well this seafloor environment is currently sampled; (III) reviewed how sample repositories/databases are currently used; and, (IV) evaluated justifications for acquiring new samples. Each breakout session culminated with a discussion of (V) what important science questions could be addressed soon (5–10 years), with existing or forthcoming assets and technologies, versus (VI) what might take longer (10+ years) and/or require the development of new assets or technologies. These motivating topics fed into the second day of discussions, which focused on “Aligning seafloor sampling technology with critical science questions.” Groups were guided by a common set of prompts, including what current resources were essential to the participants’ research, and what were the greatest challenges they faced in recovering the materials needed. The participants also discussed whether they could acquire the materials needed to address their science questions given current US assets (Figure 1 in FUTURE 2024 PI-team, 2024, AGU Advances 2024AV001560), how sample repositories and databases could be optimized for science needs, and the justification for acquiring or developing new technologies. 

Vigorous seepage offshore Oregon provides insight into the relationship between margin permeability and megathrust slip behavior. 

Abstract We address in situ serpentinization and mineral carbonation processes in oceanic lithosphere using integrated field magnetic measurements, rock magnetic analyses, superconducting quantum interference device (SQUID) microscopy, microtextural observations, and energy dispersive spectroscopy phase mapping. A representative suite of ultramafic rock samples were collected, within the Atlin ophiolite, along a 100‐m long transect across a continuous outcrop of mantle harzburgite with several alteration fronts: serpentinite, soapstone (magnesite + talc), and listvenite (magnesite + quartz). Strong correlations between changes in magnetic signal strengths and amount of alteration are shown with distinctive contrasts between serpentinite, transitional soapstone, and listvenite that are linked to the formation and breakdown of magnetite. While previous observations of the Linnajavri ultramafic complex indicated that the breakdown of magnetite occurred during listvenite formation from the precursor soapstone (Tominaga et al., 2017,https://doi.org/10.1038/s41467-017-01610-4), results from our study suggest that magnetite destabilization already occurred during the replacement of serpentinite by soapstone (i.e., at lower fluid CO₂concentrations). This difference is attributed to fracture‐controlled flow of sulfur‐bearing alteration fluid at Atlin, causing reductive magnetite dissolution in thin soapstone zones separating serpentinite from sulfide‐mineralized listvenite. We argue that magnetite growth or breakdown in soapstone provides insight into the mode of fluid flow and the composition, which control the scale and extent of carbonation. This conclusion enables us to use magnetometry as a viable tool for monitoring the reaction progress from serpentinite to carbonate‐bearing assemblages in space and time with a caution that the three‐dimensionality of magnetic sources impacts the scalability of measurements. 

Abstract Recent changes in US oceanographic assets are impacting scientists' ability to access seafloor and sub‐seafloor materials and thus constraining progress on science critical for societal needs. Here we identify national infrastructure needs to address critical science questions. This commentary reports on community‐driven discussions that took place during the 3‐dayFUTURE of US Seafloor Sampling Capabilities 2024 Workshop, which used an “all‐hands‐on‐deck” approach to assess seafloor and sub‐seafloor sampling requirements of a broad range of scientific objectives, focusing on capabilities that could be supported through the US Academic Research Fleet (US‐ARF) now or in the near future. Cross‐cutting issues identified included weight and size limitations in the over‐boarding capabilities of the US‐ARF, a need to access material at depths greater than ∼20 m below the seafloor, sampling capabilities at the full range of ocean depths, technologies required for precise navigation‐guided sampling and drilling, resources to capitalize on the research potential of returned materials, and workforce development.