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STONE circles on Mars are prompting a rethink about the planet’s ancient climate.

Using cameras on NASA’s Mars Reconnaissance Orbiter, Matt Balme of the Open University in Milton Keynes, UK, and his colleagues mapped the Elysium Planitia, a region near the equator. They saw rings up to 23 metres across made up of stones sorted by size into concentric bands .

On Earth, similar structures form via repeated freezing and thawing of ice, but with the stones sorted into layers. Water in soil under stones freezes faster than in surrounding soil, and the expanding ice pushes the stones upwards. Larger stones rise faster, and so layers sorted by size form.

What sorts the material concentrically is a mystery, but if a freeze-thaw mechanism was responsible, there must have been liquid water near the surface recently. This would mean that the climate was once 40 to 60 °C warmer than conventional estimates suggest.

Peter Grindrod from University College London thinks that the circles “would be an interesting target to look for evidence of past water on Mars”.

Stone circles found on Mars

BRAIN activity that is “scrambled” in deaf cats develops normally if they are fitted with a cochlear implant shortly after birth. The finding may explain how deaf children given implants as babies can learn to speak almost as well as hearing children.

In hearing animals, sound vibrates hair cells in the inner ear, triggering neurons to send impulses to the brain. In deaf animals, these hair cells are often defective; cochlear implants compensate by stimulating neurons directly.

To see how this artificial stimulation affects the brain, Rob Shephard at the Bionic Ear Institute in Melbourne, Australia, and colleagues recorded electrical activity in the cortex of 17 8-month-old cats that were deaf from birth. As they monitored the cats’ brains, they activated each cat’s cochlear implant.

Ten of the cats had received the implant relatively recently and their electrical activity was “completely scrambled”, indicating that they did not perceive sound coherently: normal cortex activity

is key to perceiving sound and, in humans, to developing speech.

In the seven cats that received implants at 8 weeks old, however, activity was similar to that in hearing cats (The Journal of Comparative Neurology, DOI: 10.1002/cne.21886).

Some deaf people say it is unethical to operate on deaf babies , who would otherwise learn sign language. Neurologist Jim Pickles at the University of Queensland, Australia, says the latest work “increases the weight of evidence to implant children early”.

Cochlear implants prevent ‘scrambling’ in deaf brains

IF YOU are frying a steak and mindful of your health, then marinate it in either beer or red wine. So say food scientists who measured amounts of a family of carcinogens found in fried steaks after steeping them in booze.

Cooking food increases levels of cancer-causing compounds called heterocyclic amines (HAs) . Fried and grilled meat are particularly high in these compounds, because fiery temperatures convert the sugars and amino acids in muscle tissue into HAs. Various substances can reduce HA content: an olive oil, lemon juice and garlic marinade cut HAs in grilled chicken by 90 per cent, while red wine reduced HAs in fried chicken.

Now Isabel Ferreira and colleagues at the University of Porto in Portugal have looked at the effects of beer and red wine marinades on fried steak. Six hours of marinating in beer or red wine slashed levels of two types of HA by up to 90 per cent compared with unmarinated steak (Journal of Agricultural and Food Chemistry, DOI: 10.1021/jf801837s).

For a third type of HA, beer was more efficient at reducing its content than wine, cutting levels significantly in 4 hours, while wine took 6. Beer contains more water-retaining sugars than wine and Ferreira says that may hinder the transport of water-soluble molecules to the steak’s surface, where high heat converts them into HAs. Tasters also preferred the smell, taste and appearance of beer-marinated steak.

Beer and wine for a healthier steak

A NEARBY galaxy may have been mangled in a hit-and-run by a speeding cloud of dark matter.

Astronomers have long struggled to explain the lopsided shape of the Large Magellanic Cloud, a nearby dwarf galaxy (pictured). Many galaxies feature a central bar-shaped concentration of stars, but the one in the LMC is offset from its middle.

A recent collision with another galaxy might explain it, but none of those visible nearby have a trajectory that traces back to the LMC. Now simulations by Kenji Bekki at the University of New South Wales in

Sydney, Australia, suggest that the LMC was struck by an invisible cloud of dark matter. During the collision, the pull of the dark matter’s gravity would have shifted the galaxy’s outer stars relative to the bar in the centre, producing the LMC’s appearance. The study will appear in Monthly Notices of the Royal Astronomical Society.

Simulations of galaxy formation suggest numerous dark matter clouds in the right mass range should be moving around in this region, says Ben Moore of the University of Zurich, Switzerland. But Bekki’s models may exaggerate the effect of a dark matter cloud on the LMC, he adds, because to simplify the calculations they assumed an unrealistic concentration of the dark matter’s mass at a single point.

Dark matter trashed galactic neighbour

www.newscientist.com 3 January 2009 | NewScientist | 13