The Investigating Ocean Worlds project, or InvOW, will focus on improving how future missions interpret measurements of carbon-rich molecules that could indicate biological activity. Principal investigator Chris German, a senior scientist at WHOI, and the InvOW team will examine how physical, chemical, and possible biological processes on ocean worlds such as Europa and Enceladus influence the organic signatures that spacecraft detect when searching for life.

"If you are alive today, this is the first generation where the question of whether there is life elsewhere in the universe could be answered in your lifetime," said German. "Previously, this was an abstract, intellectual, and philosophical question. We now know enough to say that it is entirely plausible that there is life out there, within humanity's reach, and we just need to go and look."

InvOW links 16 laboratories across the United States and combines ocean, polar, and space science expertise using theoretical modeling, laboratory experiments, and fieldwork. The collaboration will investigate three major domains on ocean worlds: the rocky subseafloor, the overlying ocean, and the outer ice shell or cryosphere. A key objective is to track how organic materials that may be associated with life are altered as they move through these domains before they reach a spacecraft's detection system.

German noted that distinguishing biological carbon compounds in these environments will be demanding. "Identifying carbon compounds on ocean worlds that would provide unambiguous evidence for the presence of life is challenging," explained German. On Earth, ocean ecosystems use most available organic carbon, so biologically produced molecules stand out clearly against a relatively low non-biological background. On more distant ocean worlds that receive less solar energy, non-biological organic matter may be more abundant than any material produced by life, making the background signal dominant.

Under those conditions, separating potential biosignatures from abiotic organics becomes a central task. "On ocean worlds, identifying valid indicators of life might be a needle-in-a-haystack kind of problem," said German. "Seeing through the background noise to be able to pick out signals that are definitively due to life will require rigorous examination. We need to rule out all of the other ways that signals could be generated, by non-life processes, so that they don't otherwise confound mission scientists."

InvOW deputy principal investigator Tori Hoehler, Director of the Center for Life Detection at NASA's Ames Research Center, underscored the value of preparatory research for upcoming missions. "With focused research, there's a lot that can be done-a tremendous amount of groundwork that can be laid- to optimize the design and scientific yield of future missions," said Hoehler. "The InvOW award gives us the opportunity to do just that, by bringing together planetary scientists and Earth oceanographers to understand alien oceans the way we understand our own-as complex systems where geology, physics, chemistry, and possibly biology, work together in concert. That perspective, and our team's ability to fluidly integrate a diversity of expertise, has been and will be at the heart of our efforts to conduct the foundational science on which future exploration will be built."

Project co-investigator Susan Lang, an associate scientist at WHOI, highlighted the need to track life's chemical traces from their formation to where spacecraft can sample them. "As we search for signs of life beyond Earth, it is essential to understand not only how those signs are first produced, but also the forces that shape and obscure them over time," said Lang. "This project is especially compelling because it takes a planetary-scale view, exploring how processes ranging from below the ocean to the surfaces of ice sheets affect the life signatures that rise to the outermost layers of an ocean world, where future missions will search for evidence of life."

InvOW co-investigator Brandy Toner, a professor in the Department of Soil, Water, and Climate at the University of Minnesota Twin Cities, noted how the project builds on decades of work. "This project is exciting because it pulls together all 25 years of my academic, scientific, and professional experiences," said Toner. "It is humbling and motivating because the work pushes me to the edges of my knowledge and requires the insights, innovation, and genuine collaboration of 15 other research teams. It is our job to help NASA apply what we have learned about Earth's oceans to other places in our solar system; what to expect, what to measure, how to interpret data returns, and maybe someday, sample returns. As a kid, I wanted to be an astronaut. I think this might be even better."

The InvOW project extends previous NASA-funded work under the Exploring Ocean Worlds initiative, or ExOW, which German also led with many of the same collaborators. ExOW concentrated on physical and geological processes on ocean worlds, while InvOW turns to the challenge German sees as central for upcoming missions: interpreting organic molecules detected by spacecraft, starting with Europa Clipper. During the cruise phase to Europa, the team aims to refine how to distinguish organic compounds that signal life or habitability from those that do not point to any specific biological process.

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