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1 June 2013 | NewScientist | 17 Earth won’t end up as a Venus-like hell PHEW! Earth’s evil twin Venus was born that way, so our planet may not be destined to become a hellish wasteland, after all. Venus and Earth are the same size, made of similar materials and are next-door neighbours in the solar system. But while Earth is wet and lush with life, Venus is desiccated, acidic and very hot. Planetary scientists have long assumed that whatever happened to Venus to send it down this dark path could one day befall Earth. Now, Keiko Hamano of the University of Tokyo, Japan, and colleagues have created a new model that suggests Venus was always that way. Heat from the collisions that form planets leaves infant worlds covered in molten magma. Earth and Venus may have formed atmospheres of steam that held some of the heat. According to Hamano, planets like Earth that form far enough from the sun can cool within a few million years, their steamy atmospheres condensing into liquid oceans. By contrast, the atmospheres of planets like Venus born closer to the sun would be stripped away by the solar wind before they could form oceans (Nature, DOI: 10.1038/nature12163). Was louse with jumbo sperm the forerunner of copulation? THE male produces a single sperm, wraps it in a package, and sticks it on the female’s abdomen. It’s then up to her to transfer this lone giant sperm into her genital tract. Most insects abandoned this primitive mating system millions of years ago, but it turns out the ground louse, Zorotypus impolitus, has stuck with it. Romano Dallai of the University of Siena in Italy inspected sperm packages, or spermatophores, that males left on female ground lice. He found that they were small packages concealing a large surprise. Each was just 0.1 millimetres across, but the solitary sperm it held was about 3 millimetres long, uncoiled – roughly the same length as the female (Naturwissenschaften, doi.org/mks). Males generally want to maximise their chances of fertilising eggs, so why produce only one giant sperm? Dallai says it may be a way of outcompeting other males. “The sperm is so large, it can fill the space in the female’s [genital tract],” he says. That plugs it up, IT MAKES you scratch just thinking about it: a protein that plays a central role in itching. Its discovery could lead to new ways to treat skin conditions. Mark Hoon at the National Institute of Dental and Craniofacial Research in Bethesda, Maryland, and colleagues found that killing certain spinal nerves in mice stops them from feeling itchy sensations. They also stopped making a protein called neuropeptide natriuretic polypeptide B (NPPB). To pin down its role, the team genetically engineered mice to lack the protein. These mice hardly responded when compounds that cause itching, like histamine, were daubed on their skin. Injecting NPPB into the mice’s skin produced no effect. But injecting it into the spine made both genetically engineered and ordinary mice scratch themselves furiously with their hind paws (Science, doi.org/mms). Hoon hopes that the findings will hint at new treatments for itchy skin conditions such as eczema and psoriasis. But NPPB also plays a role in the heart, so it is unlikely to be a good target for itch-relieving drugs. Instead, Hoon hopes to identify other target proteins involved in itching. Protein clue to itchy skin complaints PLAINPICTURE/MYLÈNE BLANC ensuring no other male can mate with her. In this respect, Z. impolitus is something of an exception among winged insects. All others have evolved to mate by copulation, where males insert their sperm directly into females. But some primitive wingless insects still reproduce by external sperm transfer, with males depositing a spermatophore on the ground for females to pick up. Z. impolitus, Dallai says, may represent an intermediate stage in the evolution of true copulation. Ancient bling was out of this world THINK iron jewellery is down-to- earth? Not for the ancient Egyptians, it wasn’t. A 5300-year-old necklace bead found in an Egyptian tomb was made with iron from a meteorite. Evidence for iron smelting in Egypt dates back to the 6th century BC, but archaeologists have found much older iron artefacts in the region, including in Tutankhamun’s tomb. Such artefacts are “pretty much exclusive to high-status tombs”, says Diane Johnson of the Open University in Milton Keynes, UK. Previous analyses of the oldest of these – nine iron beads from a cemetery near the Nile – proved inconclusive on their origins. Now Johnson and colleagues have taken another look at one of the beads (pictured, below) and concluded that it is indeed from a meteorite. The surface of the bead had low levels of nickel, but the levels inside were as high as they would be in a meteorite. But the clincher was evidence of a distinctive crystal structure – known as the Widmanstätten pattern – that only forms when iron and nickel cools very slowly, as it does in meteoroids (Meteoritics & Planetary Science, doi.org/mmb). It is “very convincing” that the beads come from a meteorite, says Meenakshi Wadhwa of the Center for Meteorite Studies at Arizona State University in Tempe. ANDY TINDLE/OPEN UNIVERSITY For new stories every day, visit newscientist.com/news
