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Horizons: What's new in sci-tech

New particle accelerator powers up, what bats have in common with rock stars, where to find the oldest asteroids.

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Researchers have long been intrigued with the way some birds, mammals, reptiles, insects, and other groups of creatures use Earth's magnetic fields to navigate. For birds, the compass mechanism remains somewhat mysterious. Now, researchers have shown that, in principle, light-driven chemical reactions in a bird's eye could play a key role. In essence, similar reactions could allow migratory birds to "see" the Earth's magnetic field as a visual pattern that they can use to orient themselves as they travel. The team, led by Kiminori Maeda at Oxford University, has demonstrated in the lab for the first time that the kind of chemical reactions needed to drive this visual compass can take place in a magnetic field as weak as Earth's. Until now, no one had demonstrated the effect.

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The use of a photochemical compass stands in contrast to another mechanism scientists have explored, based on the presence of tiny amounts of the mineral magnetite in the birds' bodies. Still, several scientists have inferred that a migratory songbird's eyes could play a key role in magnetic navigation. This has come in part through experiments that show that birds are unable to align themselves with Earth's magnetic field if one eye is blocked. And their ability to orient themselves seems to depend on the wavelength of ambient light. Both theory and experiments had started to narrow the mechanism down to light's interactions with chemicals in the birds' retinas. The results appear in this week's issue of the journal Nature.

Rock of ages

If you wanted to bring back a sample of some of the oldest material in the solar system, you couldn't do much better than the asteroid 234 Barbara. It lies in the main asteroid belt between Mars and Jupiter and astronomers say it's one of a trio they've found that represent the most ancient asteroids yet detected – some 4.55 billion years old.

The key to dating them lies in a unique blend of calcium and aluminum – among the first compounds thought to have condensed out of the nebula of dust and gas from which the solar system formed. A team led by University of Maryland astronomer Jessica Sunshine dated the asteroids through an analysis of the minerals' blend in meteorite samples, studies of the three asteroids, and some modeling.

They concluded that these three have remained largely free of the mixing and jumbling that have substantially altered thousands of other asteroids since the solar system formed. They contain two to three times more of these aluminum-calcium "inclusions" – and so are far older – than any meteorite that has fallen to Earth.

Knowing where these time capsules are, the team says, scientists could develop approaches to return samples. These would yield key insights into processes that took place during the first few million years the solar system was forming. The results appear in the current issue of the journal Science.

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