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September 11, 2025—The biggest black holes, the extent of hallucinogens in "magic mushroom" edibles and the role of nostalgia in keeping friends close. —Robin Lloyd, Contributing Editor | | NASA's Perseverance Mars rover took this selfie, made up of 62 individual images, on July 23, 2024. A rock nicknamed "Cheyava Falls," which bears tantalizing features suggesting it may contain ancient microbial fossils, is to the left of the rover near the center of the image. NASA/JPL-Caltech/MSSS | | - A rock analyzed by the Perseverance rover may hold proof of life on Mars. It is setting the stage for bringing Martian samples back to Earth to test for microbes on the Red Planet. | 4 min read.
- "Magic mushroom" edible products tested by researchers were found to contain no psilocybin, but most contained undisclosed ingredients, including synthetic drugs for which safety hasn't been tested in humans. | 4 min read
- One quarter of heat waves between 2000 and 2023 would have been "virtually impossible" without global warming—and can be attributed to the emissions of individual energy producers, according to a new study. | 4 min read
- Early experiments demonstrate a fast-acting antidote to carbon monoxide poisoning. The treatment relies on a new protein that snags the gas before it latches onto blood cells. | 2 min read
| | Black holes like the one shown in this illustration can grow astonishingly massive by feeding on immense amounts of matter. But just how big can they get? Pitris/Getty Images | | With findings in recent years demonstrating that a supermassive black hole sits at the center of every large galaxy, astronomers have wondered just how big black holes can get. Based on known black holes' mass measurements, which often have large uncertainties and cannot account for all the involved physics, the biggest black holes could reach a few tens of billions of solar masses, writes science communicator Phil Plait. Theoretically, it is possible, though not plausible, for a black hole to grow as large as 270 billion solar masses, one researcher estimates. It's more likely, however, that the largest supermassive black hole that astronomers will ever find "will be close to a mere 50 billion [solar masses] or so," Plait says.
How it works: The big discrepancy between the above estimates involves the rarity of anything falling into a black hole, Plait writes. Most material captured by a black hole is drawn into its orbit (not into "the cosmic dumpster's maw," Plait writes), where it forms an accretion disk. The friction generated by disk material eventually creates such heat that the intense radiation repels newer approaching matter. Magnetic fields in the disk also can pull matter away from the center of the hole. What the experts say: "The universe is smarter than we are, and it's still possible an even more colossal black hole might exist. If so, that'll give astronomers a chance to do their favorite thing: go back to their assumptions and try to figure out what they missed, learning more about these behemoths in the process. In that way, our knowledge grows, and, hopefully, there's no upper limit to that," Plait concludes. | | | Nostalgia Keeps Friendships Alive
| People who are more prone to nostalgia have a larger number of close friends, according to research by Kuan-Ju Huang, a graduate student at Kyoto University who studies emotion and social interaction, and colleagues. Also, they are more motivated to meet new people and put in the time to strengthen their existing friendships and other connections. Nostalgia earlier in life also predicted a larger network of close friends later in life, the team found in a follow-up study. How it works: The finding that nostalgia might have an impact over time was most exciting to Huang and his colleagues. Nostalgia mitigated the trend of cutting ties and losing contact with close friends as we grow older, often due to moving to a new region or focusing on raising children. What the experts say: "We suspect that nostalgia acts as a psychological resource, helping people counteract the loss of close friendships and relationships as they age. As such, it joins many other human emotions that have evolved to serve important social functions," Huang writes. | | | | |
Kang-Chun Cheng for Nature | | Erasto Job is a technician at TR├н, a company that makes electric versions of three-wheeled vehicles. Many people in Tanzania rely on such vehicles because they are among the cheapest and safest modes of transportation there, he says. He assembles the vehicles and fixes any mechanical or electrical issues that arise in TR├н's products. "I love this part of my job: tracing where the problem is coming from, figuring out how to fix it then making sure the fix works." Nature | 3 min read | | "Nostalgia is a complex emotion," wrote Kuan-Ju Huang at the start of the essay mentioned above. Sentimentality is not a useful input in many scientific settings, so I was intrigued to read about work that puts nostalgia in a new and more positive light. | | We always like to hear from you. Please send any feedback, questions or comments to: newsletters@sciam.com. —Robin Lloyd, Contributing Editor
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![To the left of the rover near the center of the image is the arrowhead-shaped rock nicknamed "Cheyava Falls, " which has features that may bear on the question of whether Mars was home to microscopic life in the distant past. The small dark hole in the rock is where Perseverance took a core sample, which is now in a sample tube stored in the rover's belly. The white patch to the right of the hole is where the rover used an abrasion tool to clear away the top surface, allowing science instruments to study the rock's composition](https://d3k81ch9hvuctc.cloudfront.net/company/WEer5A/images/b3bac55e-57f3-4a0a-aa68-068af2a0935e.png "To the left of the rover near the center of the image is the arrowhead-shaped rock nicknamed "Cheyava Falls, " which has features that may bear on the question of whether Mars was home to microscopic life in the distant past. The small dark hole in the rock is where Perseverance took a core sample, which is now in a sample tube stored in the rover's belly. The white patch to the right of the hole is where the rover used an abrasion tool to clear away the top surface, allowing science instruments to study the rock's composition")
