SCIENCE

Scott Pletcher, a geneticist at the Huffington Center on Aging at Baylor College of Medicine in Houston, knew that the mere scent of food could block some of the life-extending effects of caloric restriction in tiny, soil-dwelling worms. So he and his colleagues conducted similar tests in flies.

Sure enough, when calorie-restricted flies -- which tend to live about 50 percent longer than normal -- were housed in containers with the smell of fresh yeast (a favorite food of flies) wafting in, the life-extending benefits of their diet were reduced by about 20 percent.

In separate tests, mutant flies with defective senses of smell lived 56 percent longer than their smell-enabled counterparts, even though they ate all they wanted.

Because odor has the same effect in worms and flies, it may affect people the same way, Pletcher said. He noted that food smells alone trigger a raft of biochemical and hormonal changes in people that, while not as intense as those that occur when eating, nonetheless appear to be implicated in the aging process.

Pletcher doubts that people can do much about the life-shortening effects of being well-fed by blocking their sense of smell alone. But exposure to food smells might blunt the life-extending effects of limiting calories, he speculated.

Further work may reveal the mechanisms that link olfaction and longevity, he said, and point the way to effective anti-aging drugs.

-- Rick Weiss

A Deeper Probe of Life on Mars

Scientists probing for life on Mars should look a little deeper, say British researchers.

Current probes might turn up evidence that life once existed on the red planet, but they have little chance of finding anything alive now because they do not drill to depths where cellular life could escape the deadly cosmic radiation that bathes the surface, according to a study published last week in the journal Geophysical Research Letters.

Researchers from University College London created a model of cosmic radiation levels at various depths on Mars, accounting for geographical differences in surface conditions. They concluded that a probe would have to dig several meters down to have any hope of finding life. Mars, unlike Earth, is not shielded from radiation by a thick atmosphere and a global magnetic field.

"It just isn't plausible that dormant life is still surviving in the near-subsurface of Mars," said lead author Lewis Dartnell. "Finding life on Mars depends on liquid water surfacing on Mars, but the last time liquid water was widespread on Mars was billions of years ago. Even the hardiest cells we know of could not possibly survive the cosmic radiation levels near the surface of Mars for that long."

The best places to look for life, he said, are in a frozen sea beneath the surface in the equatorial Elysium region and in recently formed craters.

-- Christopher Lee