Scientists once suspected that a brutal, years-long winter starved the dinosaurs following an asteroid impact 66 million years ago. New evidence suggests a more violent end: widespread firestorms that may have burned even thick-skinned dinosaurs to a crisp within hours.

The roughly six-mile-wide (10-kilometer-wide) asteroid struck Mexico's Yucatán Peninsula, excavating the Chicxulub crater and vaporizing enormous quantities of rock. Some of that material condensed into tiny droplets called spherules, which spread around the planet before falling back through Earth's atmosphere at several miles per second.

As the spherules slowed, their kinetic energy became heat, producing an intense pulse of thermal radiation. Earlier models suggested the effect would have resembled a worldwide broiler that was potentially deadly to exposed, thin-skinned animals, but not powerful enough to ignite vegetation across the globe.

A new study argues that those calculations overlooked a crucial ingredient: a thick layer of fine silicate dust formed from rock vapor that did not initially condense into spherules. Evidence for that dust emerged in 2023 from the Tanis fossil site in North Dakota, where researchers identified a layer of extremely fine, impact-derived material deposited above the spherules. A similar dust layer has since been documented at the K–Pg boundary (which divides the "age of reptiles" and the "age of mammals") in Raton Basin across the Colorado–New Mexico border.

"It reinvigorated my interest in what happened to the leftover vapor — that's where this work started," lead author Brandon Johnson, a planetary scientist at Purdue University, said in a statement.

The dust would have acted like an insulating blanket, preventing thermal radiation from escaping into space and redirecting more heat toward Earth’s surface. The researchers estimated that the surface heat pulse could have been about 3.5 times more intense than what was suggested by models considering the falling spherules alone. "We're in the realm where we might be essentially killing off everything within that first hour or two," Johnson said.

The radiation may not have directly ignited thick pieces of wood, but it exceeded ignition thresholds for grass, lichen, and pine needles, which could have fueled larger fires. The study also found that exposed terrestrial animals may have received about 17 times the thermal dose considered lethal to humans.

Animals sheltering underground or in water would have had a better chance of surviving the initial heat pulse. Afterward, the same dust may have blocked sunlight for years, triggering the prolonged "impact winter" more typically blamed for the dinosaurs' extinction.

There is, however, a missing element: the wildfire evidence that supports this dust-caused inferno theory has only been found in North America. "It could be that we will eventually find the record of completely global wildfires," said Alfio Alessandro Chiarenza, a paleontologist at University College London who was not involved in the study. "We just don't have it so far."

The study was published on July 28 in the journal JGR Biogeosciences.

Scientists have found the first triple-lobed asteroid in the asteroid belt between Mars and Jupiter — and it has a small moon to boot.

The asteroid in question is 44 Nysa, which was discovered all the way back in 1857. Of course, back then it was just a pinprick of light in the sky, and subsequent observations — including some from the Hubble Space Telescope — had failed to tell us much about Nysa. Those previous observations suggested Nysa might be bi-lobed, like many asteroids and comets such as asteroid 52246 Donaldjohanson, which NASA's Lucy mission flew past in 2025.

However, new joint observations by the Large Binocular Telescope (LBT) on Mount Graham in Arizona and the Very Large Telescope (VT) on Paranal mountain in Chile have revealed that this asteroid actually seems to have three lobes, the first such object ever seen.

"The images reveal a remarkably unusual object," said lead researcher Kate Minker of Arizona's Lowell Observatory in a statement. "The most likely explanation is that Nysa is either a contact trinary, consisting of three connected components, or an extremely irregular coherent body unlike anything we've previously observed."

Obtaining the detailed images of Nysa was not easy. Key to the success were two high contrast imaging devices, the Italian-built SHARK-VIS on the LBT and SPHERE and its ZIMPOL polarimeter on the VLT, used in conjunction with adaptive optics that counteract the blurring effect of the atmosphere.

"These observations had to be combined with specially developed image-processing techniques to further sharpen the images and remove the bright halo surrounding the asteroid, potentially hiding faint companions," said Anthony Berdeu of the European Southern Observatory.

The images showed an irregular-shaped body 47 miles (75 kilometers) at its widest point, with two notable valleys or "colli" that wrap around the asteroid's circumference and which Minker's team interprets as being the necks of the different lobes. Furthermore, the images revealed a 0.6-mile-wide (1-km-wide) moon orbiting Nysa at a distance of at least 106 miles (170 km). The moon has been designated S/2026 (44) 1 for now. And, because it was seen independently during two different observing campaigns, it was possible to observe its motion around Nysa.

"We borrowed a specialized technique from another field of astronomy, known as high-contrast imaging, to detect the small moon whose faint light was overwhelmed by the intense brightness of the primary asteroid," said Gianluca Li Causi of the SHARK-VIS team at the Italian National Institute for Astrophysics (INAF).

Nysa is named after the mythical land where the ancient Greek god Dionysus was raised by nymphs. Al Conrad of the Large Binocular Telescope Observatory finds the name fitting because Dionysus was the Greek god of theater, which for the ancient Greeks often involved wearing masks and hiding one's true identity.

"We're finally unmasking the asteroid's true nature, long after it was discovered," said Conrad.

How such a bizarre object formed remains uncertain, but Minker's team does have a couple of ideas.

The team's preferred explanation is that Nysa is a contact trinary — three asteroid bodies being held together loosely by gravity. The best alternative, the researchers say, is that Nysa once upon a time had a close encounter with a much larger asteroid that slammed into it, thereby deforming it. In these situations, modeling suggests that gravitational tidal forces could have deformed Nysa's mantle, creating Nysa's odd shape and even ripping it apart into a bunch of fragments in a string-of-peals configuration. If this is the case, then where did the other fragments go? Such events usually produce a family of asteroids all sharing the same composition, but Nysa seems to be alone (barring its moon, of course).

There could be a way to distinguish between the two possible origins. By tracking the moon's orbital velocity and period, astronomers will be able to pin down the exact mass and density of Nysa and then see which model matches it best.

Nysa has been a subject of study because it can also tell us about the birth of our own planet Earth. Nysa is more reflective than many other asteroids thanks to its surface composition that is abundant in a silicate mineral called enstatite, which lacks iron. Asteroids like this are generally called E-types, and Nysa is the largest and brightest of all of them. E-type asteroids are thought to have formed close to the sun and therefore have been identified as potential building blocks of the inner planets. If Nysa is a relic of that time, it could tell us a great deal about conditions in the inner solar system 4.5 billion years ago.

The findings can be read on the arXiv archive, and have been submitted to the journal Astronomy & Astrophysics.