On the horizon

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'Hot Jupiters' may help planets form

Earth-sized, water-drenched planets may lurk in solar systems where gas balls as big as Jupiter orbit close to their suns.

That conclusion – based on computer simulations conducted by scientists from the University of Colorado and Penn State University – are likely to arch a few eyebrows. If confirmed, they would give these "hot Jupiters" an unexpected role in planet formation.

Giant gas planets form relatively far from a star. Yet some 40 percent of the "exoplanets" found so far are hot Jupiters – orbiting close in. Gas giants larger than Jupiter have been found orbiting just 2 million miles from their sun – as if Jupiter hurtled around the sun far inside Mercury's orbit (36 million miles from the sun). Many researchers reason that these giants migrate inward from their birthplaces. As they do, their massive gravity sweeps up or ejects material that might otherwise form rocky planets at distances just right for liquid water to exist on the surfaces.

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Instead, the Colorado-Penn State simulation suggests, the gas giants' migrations might actually cause rocky material to clump together into planets and even send water-rich objects hurtling in to seed them with moisture. The study suggests that more than one-third of the hot Jupiters found so far could have Earth-like cousins with oceans miles deep.

The work is part of an effort to find likely targets for a new generation of space-based telescopes designed to hunt for Earth-like planets. The results appear in the current edition of the journal Science.

Stone-age humans in Gibraltar

Gibraltar has long been viewed as a strategic spot where the Mediterranean Sea meets the Atlantic. It now appears to have been a haven for some of the last Neanderthals in Europe as well.

A team of scientists from Europe, Canada, and Japan has unearthed 103 stone tools and a series of hearths in a deep-set cave there. They say the find indicates that Neanderthals lived there as recently as 28,000 years ago and that they used the site repeatedly. The find indicates that Neanderthals may have coexisted with anatomically modern humans longer than recent estimates suggest. Over the years, other scientists have claimed to have found similar evidence for more-recent Neanderthals. But that evidence has all been dismissed for various reasons.

Gibraltar would have been a good place to hang out, the researchers note. It would have been rich in plants and animals, as it was at an intersection of several productive ecosystems.

The research appears in today's issue of the journal Nature.

Human activity fuels fiercer storms?

The causes behind a rise in strong Atlantic hurricanes and Pacific tropical cyclones are a hot-button issue among climate scientists: Is it global warming or not? The storms draw their fuel from warm waters at the ocean's surface.

Now, an international group of scientists concludes that global warming is the probable trigger for warmer ocean-surface temperatures in the places where the storms form. The team, including researchers from the National Oceanic and Atmospheric Administration, NASA, and the Lawrence Livermore National Laboratory, used 22 climate models to see if natural cycles or a climate "forced" by industrial greenhouse-gas emissions could better account for sea-surface temperature trends.

From 1906 to 2005, "we find an 84 percent chance that external forcing explains at least 67 percent" of the increase in tropical sea-surface temperatures, the team said. Although natural cycles may still play a role, the main driver seems to be global warming. The results appear in the current issue of the Proceedings of the National Academy of Sciences.

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