8 June 2013 | NewScientist | 17

Radiation too high for Mars round trip

BAD news for wannabe Mars explorers. The round trip alone would blast you with doses of radiation that come close to the acceptable limits set by NASA.

Charged, energetic particles like cosmic rays can wreak havoc on biological tissue. Earth’s magnetic field and atmosphere serve to block or deflect most cosmic rays. Astronauts on trips to Mars would be exposed to much higher doses, but exact figures were unknown.

Now measurements from a radiation detector on NASA’s Curiosity rover have been converted into sieverts, a measure of how a given dose of radiation affects the body. A crew on a 180-day journey to Mars would receive 0.331 sieverts, and the return trip would bring that up to 0.662 (Science, doi.org/mpq). That’s close to NASA’s lower limit for risk of exposure-induced death from cancer over a lifetime – and doesn’t include any trial runs to space or time on the Red Planet.

Adding more shielding to the spacecraft would reduce the dose, but the best option may be to try to get there faster, says Curiosity scientist Cary Zeitlin of the Southwest Research Institute in Boulder, Colorado.

Elderly stars like to shred their closest planetsOLD stars make rude hosts. A survey of ageing stars offers some of the first direct evidence that the cantankerous elders often rip their nearest planets to shreds.

Planet-hunting surveys have found many sun-like stars with hot Jupiters, giant worlds in close orbits. However, hot Jupiters are rarely found around older stars called subgiants, which have burned through their fuel and puffed up to several times their original size. This is widely thought to be because the puffy stars were up to twice the mass of

the sun when they were younger, and that might have influenced where their planets formed.

To help test this notion, Kevin Schlaufman and Joshua Winn of the Massachusetts Institute of Technology tracked the positions of 142 planet-hosting stars in our galaxy. Stars are born in clusters which disperse as they age. More massive stars burn out faster, so their elderly populations are usually found closer together.

But the team found that subgiants with planets are more spread out, so are older than

WITH their brutish looks and bulk, Florida manatees don’t look like highly sensitive creatures. But in one way they are: they have a talent for sensing tiny, nanoscale vibrations.

Sometimes called sea cows, the manatees live in the shallow waters of mangroves and seagrass meadows. Despite their size, they are adept at navigating muddy waters cluttered with obstacles like fallen trees. “They can get up to 30 kilometres an hour in short bursts, and still navigate without any trouble,” says Joe Gaspard of the Mote Marine Laboratory and Aquarium in Sarasota, Florida.

Their secret is their hair. Gaspard trained two manatees, Buffett and Hugh, to approach a vibrating sphere in the water. If they sensed the vibration, they nuzzled a paddle and were rewarded with treats – apples, carrots, beets and monkey biscuits.

By restricting their hairs with meshes, Gaspard found that the hairs on their face and body were picking up the minuscule vibrations. Hugh was slightly more sensitive than Buffett, detecting movements of just 0.9 nanometres (Journal of Comparative Physiology A, doi.org/mnx).

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expected, meaning that the stars were probably about the mass of our sun in their youth. That means more of them should have hot Jupiters. So where did they go?

The best conclusion, they say, is that the stars exerted extreme gravitational forces as they swelled up, stretching out their inner planets until they fell apart. The finding hints that the same fate may lie in store for Earth when the sun puffs up into a red giant in 6 billion years’ time.

The work has been accepted by The Astrophysical Journal.

Mon dieu! French wine is from Italy

FRENCH wine is renowned. But Parisians would be shocked by the wine their ancestors started out making around 500 BC: it was an Italian white.

Patrick McGovern of the University of Pennsylvania in Philadelphia analysed 2500-year-old amphoras from the south coast of France at Lattes, formerly Lattara. This is where Etruscans from what is now Italy traded with Celtic Gauls.

Amphoras are thought to have carried wine, but surprisingly, says McGovern, no one had verified this. It matters, because Etruscan amphoras streamed into southern France from about 600 BC, then a century later, distinctive local ones started leaving. If they held wine, that could reveal a great moment in European history: the start of French winemaking, copied from an Italian model. Archaeologists suspect the Gauls adopted the Etruscan tipple in place of their own fermented fruit and honey drinks, and brought vines from the eastern Mediterranean so they could export their own.

Chemicals in the clay show both Etruscan and local amphoras at Lattes did hold wine, confirming the hypothesis for the first time (PNAS, DOI: 10.1073/pnas.1216126110). It was no Beaujolais: made of grapes, yes, but with rosemary and possibly thyme or basil added, plus pine resin like modern Greek retsina.

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