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      Check out some of the weird rocks that have turned up on Mars

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      As the Mars rover Perseverance crested the top of Witch Hazel Hill, its operators back on Earth expected amazing things. This area on the western rim of the Jezero crater, along an ancient river delta that Perseverance has been exploring since it landed in 2021, is thought to contain some of the oldest rocks on the planet’s surface. The light-toned, layered materials promise a record of a wetter time, possibly one that hosted life.

      The team did not expect what they found on March 11: a dark rock resembling a clutch of frog’s eggs. Dubbed St. Paul’s Bay, the rock looks nothing like its neighbors. Where it came from and how it formed are a mystery. More

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      A nebula’s X-ray glow may come from a destroyed giant planet

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      The decades-long mystery of a never-ending explosion of X-rays around the remains of a dead star may have finally been solved. The radiation probably originates from the scorching-hot wreckage left behind by a giant planet’s annihilation.

      This discovery stems from four decades of X-ray observations of the Helix Nebula, located 650 light-years from Earth. The stream of X-ray radiation remained effectively constant over at least 20 years, researchers report in the January Monthly Notices of the Royal Astronomical Society. The best explanation, the scientists say, is that the ruins of a Jupiter-sized world continuously fall onto the nebula’s white dwarf star, getting frazzled and glowing in X-rays. More

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      JWST spots the earliest sign yet of a distant galaxy reshaping its cosmic environs

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      The James Webb Space Telescope has caught a distant galaxy blowing an unexpected bubble in the gas around it, just 330 million years after the Big Bang.

      The galaxy, dubbed JADES-GS-z13-1, marks the earliest sign yet spotted of the era of cosmic reionization, a transformative period in the universe’s history when the first stars and galaxies began to reshape their environment, astronomers report in the March 27 Nature.

      “It definitely puts a pin in the map of the first point where [reionization] very likely has already started,” says astrophysicist Joris Witstok at the University of Copenhagen. “No one had predicted that it would be this early” in the universe’s history. More

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      A map of 14 million galaxies and quasars deepens a dark energy mystery

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      ANAHEIM, Calif. — Change is in the air. New data strengthen a hint that dark energy, long thought to be constant force in the universe, might change over time.Dark energy explains the observation that the universe’s expansion rate is accelerating. But its origins are unknown. It’s typically expected to have constant density across the billions of years of the universe’s history. So when researchers from the Dark Energy Spectroscopic Instrument, or DESI, reported in 2024 that dark energy might vary over time based on their first year of data, it shook cosmology to its core.

      Many scientists expected that the standard picture would prevail with additional data from DESI. But that hasn’t happened. Instead, with three years of DESI data, the preference for a changing, or dynamical dark energy has grown. More

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      The nearest single star to Earth has four small planets

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      The nearest single star to the sun, Barnard’s star, has a brood of planets all its own. The red dwarf star, about six light-years from Earth, hosts four close-in planets each about two to three times the mass of Mars, astronomers report in the March 20 Astrophysical Journal Letters.

      “Barnard’s star has a long history of claimed detections, but none of them could be confirmed for a long time,” says astronomer Ritvik Basant of the University of Chicago. “It’s pretty exciting to know what’s orbiting the nearest stars.” More

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      New baby pictures of the universe deepen a cosmic mystery

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      The clearest pictures yet of the newborn cosmos strengthen the prevailing model of the universe but deepen a mystery about its expansion rate.

      Measurements of this rate, known as the Hubble constant, have produced conflicting results. Cosmologists hoped that new data from the Atacama Cosmology Telescope in Chile, which examines the oldest light in the universe, would clear things up and possibly reveal physics that diverges from the standard model of cosmology. But those results, announced March 18 in a webinar, only affirmed that model. More

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      A new iron compound hints ‘primordial’ helium hides in Earth’s core

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      Scientists have coaxed one of the universe’s most stubborn elements into a new compound.

      Formed under intense pressures, the newly discovered compound packs helium atoms into crystalline iron, researchers report February 25 in Physical Review Letters. The compound joins a short list of materials that incorporate the normally unreactive element and suggests that helium from the early solar system could be stored in the iron that makes up Earth’s core.

      Helium is one of the least reactive elements on the periodic table. Like the other noble gases, helium doesn’t gain or lose electrons easily and so does not normally form chemical compounds. But under extremely high pressures, helium can interact with a few other elements, including nitrogen and sodium — and now iron, research shows.

      An iron-helium compound, shown here in artificial color using a technique called secondary ion mass spectrometry, forms under high temperature and pressure. Blue and black areas mark the background, while the orange and red area represents the sample. ©2025 Hirose et al. CC-BY-ND

      To make the new iron compound, physicist Kei Hirose of the University of Tokyo and his colleagues squeezed iron and helium together in a diamond anvil cell, a high-pressure device that subjected the elements to pressures greater than 50,000 Earth atmospheres and temperatures above 1,000 degrees Celsius. This compression formed crystals containing both iron and helium.

      The volume of the crystal formed was larger than that of a crystal of pure iron at the same pressure, the team found. The researchers attributed this increase to helium ions packing into interstitial sites, the tiny spaces between iron atoms in the crystal. But the helium atoms don’t bond directly to iron — they’re too unreactive, even at extreme conditions. More

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      Uranus emits more heat than previously thought

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      Uranus emits more energy than it gets from the sun, two new studies report — a discovery that contradicts findings from the venerable Voyager spacecraft.

      When Voyager 2 sped past Uranus on January 24, 1986, the spacecraft detected no significant excess heat from the planet, making it seemingly unique among the sun’s giant worlds. However, new observations from space- and ground-based telescopes reveal that Uranus does in fact radiate more energy than sunlight provides, two research teams report in work submitted to arXiv.org in late February. More