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Mooning About: Cassini Turns 10

cassiniNASA’s Cassini mission celebrated its tenth year last week by releasing images of the solar system’s preening beauty, Saturn, and its fawning entourage of moons and rings. Eagle-eyed researchers spotted “moonlets” plowing through the delicate rings and reported the results in this week’s issue of Nature.

The moonlets measure just 30 to 70 meters across, but most of the debris in the rings measures less than 10 meters, so the moonlets leave a traceable wake. Saturn’s rings vary in thickness from about 100 meters to slightly more than 1 km.

In the image, Epimetheus (116 km across) floats just above Titan (5150 km), the largest of Saturn’s moons. The light-colored streaks in the ring may be caused by moonlets. The dark-colored section in the middle of the ring is the 325-km-wide Encke gap, probably caused by a gravitational resonance.

Cassini has mapped 60% of Titan’s northern hemisphere, which is home to lakes, rivers, and seas of liquid methane and ethane. The southern half is slated to be mapped next.

Originally appeared in Science Magazine as a Random Sample: [html] [pdf]

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Psyching Out the Fruit Fly

Fruit fly brains are useful for studying genes implicated in neurological disorders such as Alzheimer’s and Parkinson’s disease. Getting at them, however, requires messy dissections that can damage tissue. Now, a new technique may offer a hands-off peek into the miniature mind of Drosophila.

A team led by Leeanne McGurk of the Medical Research Council’s Human Genetics Unit in Edinburgh, U.K., takes flies bred with genetic markers that make the nervous systems fluoresce (blue, in photo) and bleaches their exoskeletons, making the bodies translucent. Optical projection tomography reveals the 3D structure of the organs and allows researchers to virtually slice the flies’ brains on any axis, the authors report online on 5 September in PloS One. The procedure may one day be automated, collaborator Liam Keegan says, and–with better resolution and longer-lived fluorescence–could make hand-dissection of fruit fly brains a thing of the past.

Originally appeared in Science Magazine as a Random Sample: [html] [pdf]

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Pass the Salt

Since ancient times, people have been salting meat for storage. Now Iranian archaeologists are using the same trick to preserve the body of a man who mined some of that salt millennia ago.

The body is the sixth found since modern mining operations resumed in the Chehr Abad mine in Zanjan province in 1992. The other five are on display in museums in Tehran and Zanjan, but Iran’s Cultural Heritage, Handicrafts, and Tourism Organization says the museum specimens are degrading. So when the most recent body was unearthed this year, archaeologists decided to reinter it. Iranian, German, and British experts will meet in Iran this autumn to plan long-term preservation.

University of Oxford archaeologist Mark Pollard, who has studied samples from the remains, says the six bodies most likely belonged to miners who died in cave-ins. Pollard hopes to find out where the miners came from by comparing strontium isotopes in their bones with the isotopes in nearby areas, which the miners would have absorbed from their food and drinking water. Field surveys show no sign of habitation within 30 kilometers of the mine during the Achaemenid (550-330 B.C.E.) and Sassanid (224-651 C.E.) dynasties, when the miners lived.

Originally appeared in Science Magazine as a Random Sample: [html] [pdf]

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Multifaceted Menace

Mosquitoes can walk on water as well as any waterbug, or stick to a wall like Spiderman. Now Chinese bioengineers are figuring out what makes them such versatile pests.

A team led by C. W. Wu at the Dalian University of Technology in China mounted a mosquito‘s leg on a needle and pushed it down onto a tub of water on a digital balance. By varying the angle, they found that a single leg could hold 23 times a mosquito‘s weight before becoming submerged, they report in July’s Physical Review Letters.

Scanning electron microscope images revealed that the insect’s legs are equipped with tiny scales, each with up to a dozen longitudinal ridges connected by fine transverse ribs. The scientists speculated that air trapped between the ribs may form “nanocushions” that contribute to buoyancy, but their experiments also indicated the importance of the angle of the leg in not breaking through the surface. As the authors note, mosquitoes are equally at home on dry land. It turns out that their feet are equipped with tiny hooks and covered in adhesive hairs similar to those on a fly.

Mathematician David Hu of New York University notes that understanding water-repellent nanostructures will be useful for anyone who wants to make an all-terrain robotic insect. “If it’s ever going to fly in the rain, water repellency is going to be important.”

Originally appeared in Science Magazine as a Random Sample: [html] [pdf]