Heatwaves That Feed Themselves, Dinosaur Heme and Atoms Colder Than Ever in Orbit

Read the episode (Narration script)

Today we start with heat, finish with wasps that bothered Charles Darwin, and pass through the coldest spot anyone has managed in orbit.

Across much of the mid-latitudes, the most extreme heatwaves have been getting hotter faster than ordinary hot spells, and climate models have been underestimating that trend. A new study in Science Advances, led by Yinglin Tian at the Potsdam Institute for Climate Impact Research with colleagues including Kai Kornhuber of IIASA in Austria, offers a physical reason.

Three ingredients are involved. A dome of high pressure parks overhead, letting sunshine pour in. The soil holds water, and damp ground cools itself the way sweat cools skin: water evaporates and carries heat away. And there's the temperature itself. Using a machine-learning method built so its reasoning can be inspected, the team found that past a critical temperature those three start feeding each other. Heat dries the soil, dry soil stops cooling the surface, and the hot, dry surface helps keep the high pressure in place, which brings more heat. In Europe, that switch flips at around four degrees above a normal summer day, roughly twenty-nine Celsius. Once it's on, the loop adds about ten percent to the peak of the most extreme events, across around a quarter of the humid mid-latitude regions studied. So in a heatwave running ten degrees above normal, roughly one of those degrees is the loop.

The odd part is why models miss it. Their soils start too dry. When a heatwave begins in a model, there's little moisture left to lose, so the drying step barely happens and the loop never properly engages. You can't wring much out of a towel that's already dry. That gives modellers something specific to fix. And that threshold is being reached more often: the chance of Central Europe crossing it rose from about six percent in the early 1980s to about twenty-three percent between 2018 and 2022.

Now to northeastern Brazil, and Aratasaurus, a meat-eating dinosaur that lived about a hundred and fifteen million years ago. A team led by Kliti Grice at Curtin University in Perth looked inside its leg bones, in the tiny channels that once carried blood vessels, and found crowds of little oval bodies, each about a fiftieth of a millimetre across. They argue these are red blood cells, turned to mineral.

Fossils are full of suggestive blobs, so the real interest in this PNAS paper is the chemistry. Extracts of the bone contained heme B, the iron-holding ring at the heart of hemoglobin, along with a chemically weathered version of it. The neat check was the rock around the bone. It gave a different signal entirely, rings from chlorophyll and bacterial pigments, the stuff of plants and microbes in ancient mud. Other instruments placed the heme signal inside the oval bodies themselves, alongside a manganese mineral called hausmannite that may have sealed them up.

This isn't liquid blood, intact hemoglobin protein or DNA. And the cells are still argued over. Mary Schweitzer, who has spent decades finding soft tissue in dinosaur bone, points out that a dinosaur's red blood cells, like a bird's, should keep their nucleus and bulge in the middle. These curve inward. So: a strong case for molecules from dinosaur blood, in containers whose identity is still up for debate.

From warm blood to extreme cold. Aboard China's Tiangong space station, a team led from Peking University has chilled about twenty thousand rubidium atoms to an equivalent temperature of 9.7 picokelvin, less than ten trillionths of a degree above absolute zero. That's about a quarter of the previous record. At this scale, temperature is really a measure of how slowly the atoms drift apart once released. The cloud forms a Bose-Einstein condensate, thousands of atoms acting as one quantum wave. On the ground, gravity drags a released cloud away within a second or so. In orbit, everything falls together, so the team could watch it spread for seven seconds. They held the atoms with focused laser light rather than magnets, a first for a condensate in microgravity. The goal is exquisitely sensitive measurement, such as testing whether everything really falls at the same rate.

Back on Earth, things are loud. In Science, Hansjoerg Kunc and Rouven Schmidt of Queen's University Belfast pooled 214 experiments on 177 species, on land and in water, across six continents. Human-made noise changed at least one aspect of body, development or behaviour in eight species out of ten. Animals in noisy places were about a third less abundant. Predators put in around two and a half times the hunting effort and caught roughly a quarter fewer prey, while their prey spent more time looking over their shoulders. There are winners as well as losers, but the authors argue quiet now deserves protecting alongside habitat.

Finally, those wasps. In 1860 Darwin wrote to the botanist Asa Gray that he couldn't believe a kindly creator had made ichneumon wasps to feed "within the living bodies of caterpillars." There are more than twenty-five thousand known species of these Darwin wasps. Some paralyse their host for good, a living larder. Others let it keep eating and growing while their larva develops. Writing in Current Biology, a team led from the Museum für Naturkunde in Berlin built a family tree from 697 species and found the switch from paralysing to letting the host carry on happened at least twenty-three separate times, with no sign of any lineage going back. Lead author Bernardo Santos calls it an evolutionary ratchet. Evolution can repeat itself, but it doesn't always keep the exits open.

That's us for today. If it's warm where you are, water the garden. Turns out damp soil is doing more work than it looks.