Samples of 2.5 billion-year-old mantle rocks found at spreading ocean ridges could put bounds on models of how the planet formed. And, researchers decreased the amount of lignin in poplar tree wood, making it stronger and slower to deteriorate.‘Time Capsule’ Rocks Provide Clues About Earth’s MantleIf you’re looking to really learn about the history of our planet, look to geology. Ancient rocks can provide a time capsule of the conditions in which they formed. But even the geologic record has its limits—rocks and minerals get weathered, buried, heated, melted, and recycled over time—so geologists need to search out rare super-old geologic holdouts to tell about the earliest times.Writing in the journal Nature in July, researchers described what they can learn about the chemical history of Earth’s mantle, the geologic layer beneath the planet’s crust, from studying 2.5 billion-year-old rocks collected at spreading ocean ridges. They found that these unusual mantle rocks didn’t necessarily have to have been formed in a world with less available oxygen, but could have been produced just by the mantle layer being hotter long ago.Dr. Elizabeth Cottrell, chair of the Department of Mineral Sciences at the Smithsonian’s National Museum of Natural History, joins Ira to talk about the research and why a collection of old rocks is an important part of international scientific infrastructure.Genetically Engineering Stronger Poplar Tree WoodTrees play a big role in the fight against climate change: They can soak up carbon dioxide from the air and store it for centuries in the form of biomass. But it turns out that trees could be doing even more.In 2023, Science Friday covered how the company Living Carbon had genetically engineered poplar trees to have a more efficient photosynthesis process. This allowed the trees to grow twice as fast and store 30% more carbon biomass than regular poplars, making them ideal for the carbon credit market.Recently, researchers at the University of Maryland also experimented with genetically modifying poplar trees. But this time, they had a different goal in mind. They modified the tree to reduce the amount of lignin in its wood. This made the wood stronger without the need for harsh chemical processing. It also slowed the deterioration rate of the wood, which allows it to store carbon for longer periods.To explain more about this “super wood,” SciFri guest host Sophie Bushwick is joined by the lead plant geneticist on the study, Dr. Yiping Qi, associate professor at Department of Plant Science and Landscape Architecture at the University of Maryland.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.