PNAS Science Sessions

Water and the possibility of life on Mars

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, researchers explain what we know about the potential for water and life on Mars and what we might learn from analysis of returned samples.

In this episode, we cover: •[00:00] Introduction •[01:04] Mark Thiemens explains the importance of bringing samples from Mars back to Earth. •[02:37] Arya Udry explains the current gaps and limitations in the geological record provided by Martian meteorites. •[03:55] Bruce Jakosky explains what we currently know about the presence and history of water on Mars. •[05:26] Monica Grady explains how analyzing volatile species in Martian samples could provide insight into the planet's past climate. •[06:58] Rachel Slank describes the potential presence of liquid brines on Mars. •[08:27] Vashan Wright used recordings from a seismometer onboard NASA's InSight lander to estimate the volumes of liquid water that might be contained in the Martian mid-crust. •[10:14] Mark Sephton explains what biomarkers are and what kinds we might expect to find in Martian samples. •[11:34] Caroline Freissinet describes the discovery of long-chain organic molecules on Mars and the difficulties of conclusively identifying organic molecules as biomarkers. •[13:32] Thiemens explains the potentially far-reaching value of continuing to support the Mars Sample Return mission. •[14:37] Final thoughts and conclusion.

About Our Guest: Mark Thiemens Distinguished Professor of Chemistry and Biochemistry University of California at San Diego

Arya Udry Associate Professor – Graduate coordinator University of Nevada, Las Vegas

Bruce Jakosky Professor Emeritus University of Colorado Boulder

Monica Grady Professor Emirita Open University

Rachel Slank Postdoctoral Fellow Lunar and Planetary Institute

Vashan Wright Assistant Professor University of California, San Diego

Mark Sephton Professor Imperial College London

Caroline Freissinet Researcher Laboratory for Atmospheres, Observations, and Space French National Centre for Scientific Research

View related content here: https://www.pnas.org/doi/10.1073/pnas.2421996121 https://www.pnas.org/doi/10.1073/pnas.2415280121 https://www.pnas.org/doi/full/10.1073/pnas.2404254121 https://www.pnas.org/doi/full/10.1073/pnas.2321080121 https://www.pnas.org/doi/full/10.1073/pnas.2404260121 https://www.pnas.org/doi/full/10.1073/pnas.2321067121 https://www.pnas.org/doi/full/10.1073/pnas.2409983121 https://www.pnas.org/doi/full/10.1073/pnas.2404256121 https://www.pnas.org/doi/full/10.1073/pnas.2420580122

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Using reinforcement learning to plan for an uncertain climate future

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, Ning Lin talks about how reinforcement learning methods plant to mitigate climate risk despite uncertainty in climate change risk forecasts.

In this episode, we cover: •[00:00] Introduction •[1:04] Civil engineer Ning Lin introduces why climate forecast uncertainty complicates risk management planning. •[02:41] Lin explains how reinforcement learning works. •[03:26] She talks about why the team studied risk management for Manhattan. •[04:54] Lin explains the results of the reinforcement learning study. •[05:40] She recounts the results that surprised her. •[07:25] Lin explains the takeaways from the study for emergency planners. •[09:00] She enumerates the caveats and limitations of the study. •[10:11] Conclusion.

About Our Guest:

Ning Lin Professor Princeton University

View related content here: https://www.pnas.org/cgi/doi/10.1073/pnas.2402826122

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Insights in route planning from London taxi drivers

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, Hugo Spiers, Pablo Fernández Velasco, and Eva-Marie Griesbauer share what they learned about human route planning from talking with London taxi drivers.

In this episode, we cover: •[00:00] Introduction •[00:59] Cognitive neuroscientist Hugo Spiers reviews previous studies on human route planning. •[01:29] Cognitive scientist and philosopher Pablo Fernández Velasco talks about why they chose to study London taxi drivers. •[01:49] Spiers describes the test that qualifies London taxi drivers. •[02:39] Spiers explains the experimental procedure. •[04:01] A recording of a taxi driver describing a route. •[04:57] Fernández talks about the data analysis. •[05:22] Psychologist Eva-Maria Griesbauer talks about the experience of interviewing taxi drivers. •[05:56] Fernández, Spiers, and Griesbauer recount the results of the study. •[08:43] Fernández and Spiers talk about the implications for the study of human route planning. •[10:22] Fernández describes the caveats and limitations of the study. •[11:15] Conclusion.

About Our Guests:

Hugo Spiers Professor University College London

Pablo Fernández Velasco Postdoctoral researcher University of York

Eva-Maria Griesbauer Postdoctoral researcher University College London

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2407814122

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Individual decision-making and collective animal behavior

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, researchers explore advances in the modeling of collective animal behaviors.

In this episode, we cover: •[00:00] Introduction •[00:48] Conor Heins incorporated cognitive processes into a model of collective behavior. •[02:13] Eva Kanso analyzed how confinement influences collective behavior. •[03:41] Andreu Puy considered the role of speed in the leader-follower dynamics of schooling fish. •[04:45] Daniel Kronauer explored how a colony of clonal raider ants collectively responds to rising temperatures. •[06:02] Sonja Friman quantified the energy savings of starlings flying in complex formations. •[07:27] Daniele Carlesso modeled how weaver ants decide to form chains to explore their environment. •[08:43] Ashkaan Fahimipour explored how reef fish minimize the spread of misinformation. •[10:11] Clare Doherty explored the individualism of terrestrial hermit crabs moving in groups. •[11:44] Final thoughts and conclusion.

About Our Guests: Conor Heins Machine Learning Researcher Verses AI / Max Planck Institute of Animal Behavior

Eva Kanso Zohrab A. Kaprielian Fellow in Aerospace and Mechanical Engineering University of Southern California

Andreu Puy PhD Student Polytechnic University of Catalonia

Daniel Kronauer Stanley S. and Sydney R. Shuman Professor Rockefeller University

Sonja Friman Postdoctoral Fellow Lund University

Daniele Carlesso Postdoctoral Researcher University of Konstanz

Ashkaan Fahimipour Assistant Professor Florida Atlantic University

Clare Doherty Research Associate Ulster University

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2320239121 https://www.pnas.org/doi/full/10.1073/pnas.2406293121 https://www.pnas.org/doi/full/10.1073/pnas.2309733121 https://www.pnas.org/doi/full/10.1073/pnas.2123076119 https://www.pnas.org/doi/full/10.1073/pnas.2319971121 https://www.pnas.org/doi/full/10.1073/pnas.2216217120 https://www.pnas.org/doi/full/10.1073/pnas.2215428120 https://www.nature.com/articles/s41598-022-11469-1

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Modeling extreme heat waves

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, Kai Kornhuber explains how and why climate models struggle to reproduce extreme heat wave trends.

In this episode, we cover: •[00:00] Introduction •[00:53] Extreme weather climatologist Kai Kornhuber explains why modeling heat waves is important. •[01:38] He talks about how the study modeled hotspots of anomalous heat wave activity. •[03:01] Kornhuber tells where the hotspots are located. •[04:17] He explains how well climate models reproduce these trends. •[06:43] He talks about ways climate modelers can improve model representation of heat waves. •[07:48] Kornhuber describes the caveats and limitations of the study. •[09:08] He enumerates the key takeaways. •[10:18] Conclusion.

About Our Guest:

Kai Kornhuber Senior Research Scholar International Institute for Applied Systems Analysis

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2411258121

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Reconsidering the social cost of carbon

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, Frances Moore presents a re-analysis of how the social costs of carbon emissions are quantified.

In this episode, we cover: •[00:00] Introduction •[00:50] Climate economist Frances Moore explains the "social cost of carbon." •[02:21] She describes the background of the study. •[03:35] She talks about the methods of the study, which included a survey of experts. •[05:18] Moore presents the results, including underestimation of the social cost of carbon. •[07:02] She talks about the policy implications of the study. •[08:35] Moore discusses the caveats and limitations of the study. •[09:21] Conclusion.

About Our Guest:

Frances Moore Associate professor University of California, Davis

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2410733121

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How hula hoops stay aloft

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, Olivia Pomerenk reveals the physics of hula hooping.

In this episode, we cover: •[00:00] Introduction •[00:49] Applied mathematician Olivia Pomerenk talks about the history of hula hooping. •[01:52] Pomerenk explains the fascinating nature of hula hoop motion as well as her own personal experiences with the children's toy. •[02:44] She describes the experimental setup with robotic hula hoopers, as well as the mathematical model that arose from experiments. •[04:44] Pomerenk enumerates the forces needed for successful hula hooping. •[05:51] She explains how body shape affects hula hooping. •[07:17] She explores potential applications of the findings. •[08:01] Pomerenk discusses the caveats and limitations of the study. •[08:44] Conclusion.

About Our Guests:

Olivia Pomerenk PhD Candidate Courant Institute of Mathematical Sciences, New York University

View related content here: https://www.pnas.org/doi/10.1073/pnas.2411588121

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Erosion, subsidence, and sea level rise on Arctic coastlines

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, Roger Creel describes how compounding forces could reshape a thawing Arctic coastline.

In this episode, we cover: •[00:00] Introduction •[00:57] Sea level geophysicist Roger Creel introduces the importance of subsidence in Arctic coastline erosion. •[02:04] Creel describes his firsthand experiences seeing how erosion, subsidence, and sea level rise are impacting Alaskan communities. •[03:43] He explains how his model of coastline impacts was constructed. •[05:49] He describes the results of the study. •[06:43] Creel talks about the risks to coastal infrastructure. •[08:10] He lists the caveats and limitations of the study. •[08:54] Creel says that the coastline impacts may differ in different parts of the Arctic, depending on glacial history. •[09:25] He explains the takeaways from the study. •[10:39] Conclusion.

About Our Guests:

Roger Creel Postdoctoral scholar Woods Hole Oceanographic Institution

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2409411121

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How brains and AI systems process moving images

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, Hollis Cline describes how neuroscience informed development of an artificial intelligence movie recognition system.

In this episode, we cover: •[00:00] Introduction •[00:55] Neuroscientist Hollis Cline introduces the background of the study. •[01:49] Cline talks about the current limitations of artificial intelligence movie recognition. •[02:58] She explains why Xenopus tadpoles were used as subjects in this study. •[03:29] Cline talks about the experimental setup and procedure. •[05:53] She explains the results of tadpole neurological monitoring. •[06:32] Cline adds findings about neural plasticity and learning. •[07:53] She describes how the findings led to an artificial intelligence system and the system's capabilities. •[09:53] Caveats and limitations of the study. •[10:22] Conclusion.

About Our Guests:

Hollis Cline Professor Scripps Research Institute

View related content here: https://www.pnas.org/doi/10.1073/pnas.2412260121

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Sustainability of plant-based meat alternatives

Science Sessions are brief conversations with cutting-edge researchers, National Academy members, and policymakers as they discuss topics relevant to today's scientific community. Learn the behind-the-scenes story of work published in the Proceedings of the National Academy of Sciences (PNAS), plus a broad range of scientific news about discoveries that affect the world around us.

In this episode, researchers discuss the environmental, health, and economic tradeoffs that limit the potential benefits of plant-based meat alternatives.

In this episode, we cover: •[00:00] Introduction •[01:19] Rodolphe Barrangou explains the potential opportunities and challenges for plant-based meat alternatives to help mitigate the environmental impact of meat. •[03:18] Marco Springmann compares plant-based meat and milk alternatives with both animal-sourced foods and unprocessed plant-based foods across multiple metrics. •[05:16] Bill Aimutis highlights the potential environmental impact of producing plant-based proteins. •[07:04] Ute Weisz finds significant variability in the amino acid scores and functional properties of commercially available plant protein ingredients. •[08:51] Zachary Neuhofer analyzes trends in plant-based meat alternative consumption, based on two years of grocery store scanning data. •[10:16] Evelyne Selberherr analyzes the microbial communities found in plant-based meat alternative products. •[11:56] Matin Qaim analyzes the impact of animal-sourced foods on child nutrition in five Sub-Saharan African countries. •[13:59] Final thoughts and conclusion.

About Our Guests: Rodolphe Barrangou Todd R. Klaenhammer Distinguished Professor North Carolina State University

Marco Springmann Senior Researcher | Professorial Research Fellow University of Oxford | University College London

Bill Aimutis Executive Director North Carolina Food Innovation Lab

Ute Weisz Professor Technical University of Munich

Zachary Neuhofer PhD Candidate Purdue University

Evelyne Selberherr Assistant Professor University of Veterinary Medicine Vienna

Matin Qaim Schlegel Professor of Agricultural Economics University of Bonn

View related content here: https://www.pnas.org/doi/full/10.1073/pnas.2400495121 https://www.pnas.org/doi/full/10.1073/pnas.2319010121 https://www.pnas.org/doi/full/10.1073/pnas.2319003121 https://www.pnas.org/doi/full/10.1073/pnas.2319019121 https://www.nature.com/articles/s41598-022-16996-5 https://www.nature.com/articles/s41538-024-00269-8 https://www.pnas.org/doi/full/10.1073/pnas.2319009121

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