16 | NewScientist | 16 March 2013

IF YOU could lick Jupiter’s moon Europa, it would probably taste like seawater. A fresh look at the moon’s face has revealed magnesium salts – the best evidence yet that water can seep up from Europa’s ice-bound ocean.

The contents of this hidden ocean have long been a mystery. So Kevin Hand of NASA’s Jet Propulsion Laboratory in California and colleague Mike

Brown of the California Institute of Technology used the Keck Observatory in Hawaii to look at light reflected off Europa and tease out clues from its spectrum.

They found magnesium sulphate on the side of the moon that always faces away from Jupiter. This side is bombarded by radiation channelled by Jupiter’s magnetic field, and by sulphur from volcanoes on

Caffeine hit brings bees back for more

PLANTS may be spiking their nectar with addictive drugs to lure insects into spreading their pollen.

Geraldine Wright at Newcastle University, UK, and colleagues trained bees to associate a scent with a sugary reward. Bees given sugar water laced with caffeine were twice as likely to remember the scent – and stick their tongues out in anticipation – three days later, than bees fed on the sugar alone (Science, doi.org/kqq).

Small amounts of caffeine and other bitter chemicals such as nicotine exist naturally in the nectar of more than 100 plant species, but it was thought that plants use these to deter predators. “The fact that they are using them to manipulate behaviour in their own favour is cool,” says Serena Dudek of the US National Institute of Environmental Health Sciences in North Carolina.

The world’s biggest mouth hides a hot erectile secret

BOWHEAD whales are a superlative species with a problem. The cetacean with the world’s largest mouth and longest mammalian lifespan gets too hot. But help is at hand. It turns out it has an organ on the roof of its mouth – bizarrely similar to a penis – that helps it cool down.

In the early 1990s, Alexander Werth of Hampden-Sydney College in Virginia and colleagues dissected the heads of seven bowhead whales, killed by Alaskan hunters. The results, just published, show that each whale had a rod of tissue running along the middle of its palate made of soft, spongy tissue. The rod is filled with

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Jovian moon’s ocean has earthly flavour the neighbouring moon Io.Hand and Brown think that

magnesium chloride is welling up from Europa’s ocean and being broken down by radiation. A reaction with the sulphur then forms magnesium sulphate. Sodium and chlorine have also been seen on or around Europa, so if the ocean contains magnesium chloride, there’s a strong chance it has other chlorine salts such as sodium chloride, making the waters distinctly Earth-like.

blood vessels, and the team says it probably swells and becomes rigid when extra blood is pumped through it – much like a penis. They call it the corpus cavernosum maxillaris (The Anatomical Record, DOI: 10.1002/ar.22681).

The team found that the organ tended to stay 6 to 8 °C warmer than other tissues several hours after the whales had died. That suggests it sheds heat into the cold water, especially when engorged with warm blood.

Bowhead whales are almost too well insulated, Werth says. This keeps them keep warm in the freezing Arctic, but it may also make them prone to overheating when they’re working hard – during migrations for instance. To cool off, they simply crack open their mouths and let the cool water run over their blood-swelled palate.

A BASIC unit of cosmic distance just got a tad more precise.

Like the first centimetre on a cosmic ruler, the distance to the Large Magellanic Cloud (LMC), a small galaxy orbiting the Milky Way, is the basis for measuring how far away other objects are.

Now Grzegorz Pietrzynski of the University of Concepción in Chile and colleagues have pinned down that distance by watching binary stars. The dip in light when one star eclipses its partner can reveal the foreground star’s size. Comparing this with the size of its disc in the sky gives its distance.

Using the average distance to eight LMC binaries, the team found that the LMC is 162,900 light years away, to a record accuracy of 2.2 per cent (Nature, doi.org/kp9).

Binary stars refine cosmic centimetre

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