In the search for habitable exoplanets, atmospheric conditions play a key role in determining if a planet can sustain liquid water. Suitable candidates often sit in the “Goldilocks zone,” a distance that is neither too close nor too far from their host star to allow liquid water. With the launch of the James Webb Space Telescope (JWST), astronomers are collecting improved observations of exoplanet atmospheres that will help determine which exoplanets are good candidates for further study.

In an open-access paper published today in The Astrophysical Journal Letters, astronomers used JWST to take a closer look at the atmosphere of the exoplanet TRAPPIST-1e, located in the TRAPPIST-1 system. While they haven’t found definitive proof of what it is made of — or if it even has an atmosphere — they were able to rule out several possibilities.

“The idea is: If we assume that the planet is not airless, can we constrain different atmospheric scenarios? Do those scenarios still allow for liquid water at the surface?” says Ana Glidden, a postdoc in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS) and the MIT Kavli Institute for Astrophysics and Space Research, and the first author on the paper. The answers they found were yes.

The new data rule out a hydrogen-dominated atmosphere, and place tighter constraints on other atmospheric conditions that are commonly created through secondary-generation, such as volcanic eruptions and outgassing from the planet’s interior. The data were consistent enough to still allow for the possibility of a surface ocean.

“TRAPPIST-1e remains one of our most compelling habitable-zone planets, and these new results take us a step closer to knowing what kind of world it is,” says Sara Seager, Class of 1941 Professor of Planetary Science at MIT and co-author on the study. “The evidence pointing away from Venus- and Mars-like atmospheres sharpens our focus on the scenarios still in play.”

The study’s co-authors also include collaborators from the University of Arizona, Johns Hopkins University, University of Michigan, the Space Telescope Science Institute, and members of the JWST-TST DREAMS Team.

Improved observations

Exoplanet atmospheres are studied using a technique called transmission spectroscopy. When a planet passes in front of its host star, the starlight is filtered through the planet’s atmosphere. Astronomers can determine which molecules are present in the atmosphere by seeing how the light changes at different wavelengths.

“Each molecule has a spectral fingerprint. You can compare your observations with those fingerprints to suss out which molecules may be present,” says Glidden.

JWST has a larger wavelength coverage and higher spectral resolution than its predecessor, the Hubble Space Telescope, which makes it possible to observe molecules like carbon dioxide and methane that are more commonly found in our own solar system. However, the improved observations have also highlighted the problem of stellar contamination, where changes in the host star’s temperature due to things like sunspots and solar flares make it difficult to interpret data.

“Stellar activity strongly interferes with the planetary interpretation of the data because we can only observe a potential atmosphere through starlight,” says Glidden. “It is challenging to separate out which signals come from the star versus from the planet itself.”

Ruling out atmospheric conditions

The researchers used a novel approach to mitigate for stellar activity and, as a result, “any signal you can see varying visit-to-visit is most likely from the star, while anything that’s consistent between the visits is most likely the planet,” says Glidden.

The researchers were then able to compare the results to several different possible atmospheric scenarios. They found that carbon dioxide-rich atmospheres, like those of Mars and Venus, are unlikely, while a warm, nitrogen-rich atmosphere similar to Saturn’s moon Titan remains possible. The evidence, however, is too weak to determine if any atmosphere was present, let alone detecting a specific type of gas. Additional, ongoing observations that are already in the works will help to narrow down the possibilities.

“With our initial observations, we have showcased the gains made with JWST. Our follow-up program will help us to further refine our understanding of one of our best habitable-zone planets,” says Glidden.

Just a few months after Elon Musk’s retreat from his unofficial role leading the Department of Government Efficiency (DOGE), we have a clearer picture of his vision of government powered by artificial intelligence, and it has a lot more to do with consolidating power than benefitting the public. Even so, we must not lose sight of the fact that a different administration could wield the same technology to advance a more positive future for AI in government.

To most on the American left, the DOGE end game is a dystopic vision of a government run by machines that benefits an elite few at the expense of the people. It includes AI ...

"I wanted to choke some people," Cameron Hamilton said in a podcast interview last week.

Energy Secretary Chris Wright said he would promote natural gas during his upcoming trip to Europe.

Major transportation systems are cutting bus and rail service in an effort to stay afloat.

The potential is enormous. So are the hurdles of getting the water out and puzzling over who owns it, who uses it and how to extract it.

A nascent carbon market faces questions about whether it reduces emissions and if nations are unfairly getting credit for climate projects.

The bloc’s biggest players want to delay a vote on the 2040 emissions-cutting milestone.

More than 1,900 fires have been sparked across the EU, scorching a record 3,806 square miles.

With some 4 million people now living in Dubai, compared with around 255,000 in 1980, pressure on water consumption continues.

Nature Climate Change, Published online: 08 September 2025; doi:10.1038/s41558-025-02433-8

Election and policy inaction

Nature Climate Change, Published online: 08 September 2025; doi:10.1038/s41558-025-02431-w

Activity changes during heatwaves

Nature Climate Change, Published online: 08 September 2025; doi:10.1038/s41558-025-02432-9

Unpredictable impacts of previous stress

Nature Climate Change, Published online: 08 September 2025; doi:10.1038/s41558-025-02430-x

Understanding unexpected slowdown

Nature Climate Change, Published online: 08 September 2025; doi:10.1038/s41558-025-02440-9

Terrestrial ecosystems take up approximately a third of anthropogenically emitted carbon and are a key component of climate mitigation strategies. However, recent evidence indicates constraints on land-based carbon uptake and mitigation potential.

Nature Climate Change, Published online: 08 September 2025; doi:10.1038/s41558-025-02398-8

Few studies have evaluated how climate change may affect dietary habits and nutritional health. Here, using transaction data in the USA, the authors show that added sugar consumption increases with temperature, especially between 12 °C and 30 °C, with stronger effects among lower-income and lower-education groups.

Nature Climate Change, Published online: 08 September 2025; doi:10.1038/s41558-025-02426-7

Scientists increasingly assess interventions against misinformation mainly via truth discernment. However, pursuing truth discernment may not be sufficiently beneficial to society if interventions do not improve behaviour and other outcomes.

Artificial intelligence optimization offers a host of benefits for mechanical engineers, including faster and more accurate designs and simulations, improved efficiency, reduced development costs through process automation, and enhanced predictive maintenance and quality control.

“When people think about mechanical engineering, they're thinking about basic mechanical tools like hammers and … hardware like cars, robots, cranes, but mechanical engineering is very broad,” says Faez Ahmed, the Doherty Chair in Ocean Utilization and associate professor of mechanical engineering at MIT. “Within mechanical engineering, machine learning, AI, and optimization are playing a big role.”

In Ahmed’s course, 2.155/156 (AI and Machine Learning for Engineering Design), students use tools and techniques from artificial intelligence and machine learning for mechanical engineering design, focusing on the creation of new products and addressing engineering design challenges.

“There’s a lot of reason for mechanical engineers to think about machine learning and AI to essentially expedite the design process,” says Lyle Regenwetter, a teaching assistant for the course and a PhD candidate in Ahmed’s Design Computation and Digital Engineering Lab (DeCoDE), where research focuses on developing new machine learning and optimization methods to study complex engineering design problems.

First offered in 2021, the class has quickly become one of the Department of Mechanical Engineering (MechE)’s most popular non-core offerings, attracting students from departments across the Institute, including mechanical and civil and environmental engineering, aeronautics and astronautics, the MIT Sloan School of Management, and nuclear and computer science, along with cross-registered students from Harvard University and other schools.

The course, which is open to both undergraduate and graduate students, focuses on the implementation of advanced machine learning and optimization strategies in the context of real-world mechanical design problems. From designing bike frames to city grids, students participate in contests related to AI for physical systems and tackle optimization challenges in a class environment fueled by friendly competition.

Students are given challenge problems and starter code that “gave a solution, but [not] the best solution …” explains Ilan Moyer, a graduate student in MechE. “Our task was to [determine], how can we do better?” Live leaderboards encourage students to continually refine their methods.

Em Lauber, a system design and management graduate student, says the process gave space to explore the application of what students were learning and the practice skill of “literally how to code it.”

The curriculum incorporates discussions on research papers, and students also pursue hands-on exercises in machine learning tailored to specific engineering issues including robotics, aircraft, structures, and metamaterials. For their final project, students work together on a team project that employs AI techniques for design on a complex problem of their choice.

“It is wonderful to see the diverse breadth and high quality of class projects,” says Ahmed. “Student projects from this course often lead to research publications, and have even led to awards.” He cites the example of a recent paper, titled “GenCAD-Self-Repairing,” that went on to win the American Society of Mechanical Engineers Systems Engineering, Information and Knowledge Management 2025 Best Paper Award.

“The best part about the final project was that it gave every student the opportunity to apply what they’ve learned in the class to an area that interests them a lot,” says Malia Smith, a graduate student in MechE. Her project chose “markered motion captured data” and looked at predicting ground force for runners, an effort she called “really gratifying” because it worked so much better than expected.

Lauber took the framework of a “cat tree” design with different modules of poles, platforms, and ramps to create customized solutions for individual cat households, while Moyer created software that is designing a new type of 3D printer architecture.

“When you see machine learning in popular culture, it’s very abstracted, and you have the sense that there’s something very complicated going on,” says Moyer. “This class has opened the curtains.” 

New research (paywalled):

Editor’s summary:

Cephalopods are one of the most successful marine invertebrates in modern oceans, and they have a 500-million-year-old history. However, we know very little about their evolution because soft-bodied animals rarely fossilize. Ikegami et al. developed an approach to reveal squid fossils, focusing on their beaks, the sole hard component of their bodies. They found that squids radiated rapidly after shedding their shells, reaching high levels of diversity by 100 million years ago. This finding shows both that squid body forms led to early success and that their radiation was not due to the end-Cretaceous extinction event...

I am pleased to announce the imminent publication of my latest book, Rewiring Democracy: How AI will Transform our Politics, Government, and Citizenship: coauthored with Nathan Sanders, and published by MIT Press on October 21.

Rewriting Democracy looks beyond common tropes like deepfakes to examine how AI technologies will affect democracy in five broad areas: politics, legislating, administration, the judiciary, and citizenship. There is a lot to unpack here, both positive and negative. We do talk about AI’s possible role in both democratic backsliding or restoring democracies, but the fundamental focus of the book is on present and future uses of AIs within functioning democracies. (And there is a lot going on, in both national and local governments around the world.) And, yes, we talk about AI-driven propaganda and artificial conversation...