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A New Cross-Disciplinary Collaboration for Upcoming NASA Missions and Mission Concepts

Scientists have long been captivated by the possibility of discovering evidence for extraterrestrial life in the universe. While many of the world鈥檚 largest telescopes are pointed toward distant galaxies and star systems, some think there鈥檚 a strong possibility that life could be detected much closer to home.

In a new collaboration with a scientist at NASA鈥檚 (JPL), Professor Nagissa Mahmoudi of the Department of Earth and Planetary Sciences is investigating potential biosignatures on two of our solar system鈥檚 moons: Europa, orbiting Jupiter, and Enceladus, orbiting Saturn. Despite thick layers of solid ice and dramatically low surface temperatures, scientists think that, under the surface, these water worlds could possess the right conditions to support microbial life.

It鈥檚 an unexpected avenue of research for Mahmoudi, a geomicrobiologist who studies how microbes interact with organic compounds in deep-sea environments on Earth. 鈥淭he study of organic molecules in our oceans has revealed chemically stable compounds dating back thousands of years, thanks to microbial processes,鈥� she explained. 鈥淥ur hunch is that if there is life under the icy surfaces of these ocean moons, we may be able to detect it in the form of microbial byproducts.鈥�

While the icy shells of Europa and Enceladus are thought to be up to tens of miles thick, both moons show signs of hydrothermal activity below the surface, which could create environments hospitable to life. Observations have also revealed at least 100 watery jets erupting from Enceladus, and there are indications that similar plumes may exist on Europa. An orbiting spacecraft could potentially pass through these plumes, researchers say, and analyze their icy particles. Doing so may provide new insights into chemical or even biochemical processes taking place deep below the icy surface.

With NASA鈥檚 set to launch in 2024, Mahmoudi and her collaborator, JPL Research Scientist , are working to test this theory using the same advanced scientific instrumentation that will be aboard the spacecraft when it departs Earth. (While no mission to Enceladus is currently in progress, the proposed Enceladus Orbilander mission concept envisions a potential departure in the 2030s.) If mission control knows what to look for, the thinking goes, it will help them determine which measurements to take 鈥� and how to interpret them 鈥� when the spacecraft arrives at its destination.

But what might alien microbial life look like, and how would we know if we found it? Working out of her lab in the Adams Building, Mahmoudi and her students are cultivating, under highly controlled conditions, a diverse range of different microbes found in deep-sea hydrothermal environments. These microbes could hypothetically appear in the oceans of Europa and Enceladus, given what is known and hypothesized about conditions on these gelid moons. Mahmoudi鈥檚 team will then isolate their metabolic byproducts 鈥� in other words, their 鈥榩oop鈥� 鈥� to get a better sense of what these compounds might look like in a plume.

鈥淭he reason we鈥檙e looking at byproducts is that we know, at least in ocean environments on Earth, they are stable and stick around a lot longer than life itself,鈥� Mahmoudi said. 鈥淔or this reason, we think byproducts are ideal to explore as potential biosignatures, as they are more likely to persist in environments such as the plume of Enceladus or the surface of Europa. In addition, they are detectable with current instrumentation, including the instruments that will be aboard the Europa Clipper mission.鈥�

Next, these samples will be shipped off to Cable鈥檚 lab at JPL for analysis with mass spectrometry to gain a deeper understanding of their chemical profiles. Using technology available at Caltech and JPL, Cable will replicate a close flyby of Europa by the spacecraft, creating icy particles sputtered from the moon鈥檚 surface or emitted via a plume and impacting them at spacecraft flyby velocities (~3 km/s). By analysis of the post-impact products in the same way as the instrument aboard Europa Clipper, Cable and Mahmoudi will test whether the scientific payload will be capable of detecting and distinguishing these microbial byproducts鈥� unique chemical signatures.

If the team can isolate distinct chemical 鈥榝ingerprints鈥� for life and confirm the possibility of measuring them in upcoming missions and proposed mission concepts to these watery moons, the implications could be profound. 鈥淭his is a new avenue for my research, and I鈥檓 excited to see where it goes,鈥� Mahmoudi said. 鈥淚t鈥檚 a thrill to work on such a fundamental mystery, and I hope our proposed work helps us develop a better understanding of the possibilities for extraterrestrial life in our universe.鈥�

Mahmoudi and Cable鈥檚 collaboration emerged at a recent meeting of the , sponsored by the and the . The gathering brought together some 50 early-career scientists from a wide range of disciplines to exchange ideas on developing new approaches to the search for extraterrestrial biosignatures. In a breakout room during the meeting, Mahmoudi and Cable started a casual discussion about the potential for deep-sea research on Earth to advance understanding of biosignatures on Europa and Enceladus. Before the end of the meeting, they had written up a joint proposal and pitched it to the event sponsors, which awarded them a one-year grant to pursue their novel research.

Learn more about the event and the supported research at the .

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