Earth's gravity makes asteroids go pale
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14 | NewScientist | 23 January 2010 IS IT a bird, is it a plane? No, it’s a rock falling into a pool of water, but the jet of air it produces flies faster than a speeding bullet. When an object such as a pebble drops into water, an air-filled cavity is created which ejects air at supersonic speeds, discovered Stephan Gekle at the University of Twente in the Netherlands, and colleagues. Using high-speed photography, the team spotted a cavity of air forming in an hourglass shape – with the top of the hourglass at the surface of the water and its base at the sinking object. To measure the speed of air rushing out upwards, they marked the air with smoke before the splash. Even though their camera took 15,000 frames per second, they still couldn’t measure the fastest speeds directly, so they simulated Pregnant drinking alters fetal DNA DRINKING too much while pregnant chemically alters the fetus’s DNA and changes gene activity, a study in mice suggests. When a pregnant woman drinks excessively, fetal alcohol syndrome can do permanent damage to her child. Suyinn Chong at the Queensland Institute of Medical Research in Herston, Australia, wondered whether “epigenetic” chemical changes to DNA – changes not in the genetic code itself but in the activity of certain genes – might be to blame. Chong’s team bred mice with genes for brown and yellow fur that are known to be modified by epigenetics. The offspring of mothers that drank alcohol were brown more often than you would expect from their DNA alone, indicating that alcohol had altered fetal gene activity (PLoS Genetics, DOI: 10.1371/journal.pgen. 1000811). These mice also weighed less and had smaller skulls. Tentacled snakes can feel their way to a midnight feast THE mysterious moustache of an aquatic snake may help it “see” in murky waters by detecting subtle currents generated by its prey. Ken Catania and colleagues at Vanderbilt University in Nashville, Tennessee, used a hair to deflect the upper-lip tentacles of tentacled snakes (Erpeton tentaculatum), and recorded the resulting nerve activity. The tentacles proved to be exquisitely sensitive to even the tiniest deflection. Mapping the path of the tentacle nerves showed that they feed into an area of the brain that processes sensory signals, close to where it responds strongly to visual CHRIS MATTISON/FLPA IN BRIEF Little splash makes a supersonic air jet the behaviour they had observed. They found that shortly before the cavity closes, the pressure of the air at the bottom of the hourglass becomes higher relative to the “neck”. This difference pushes the air out at speeds faster than sound (Physical Review Letters, DOI: 10.1103/PhysRevLett.104.024501). Jeffrey Aristoff of Princeton University is impressed by the research. The presence of supersonic flow was far from obvious, he says. signals. “This suggests that [the snakes] are putting the two parts of the information together,” Catania says. To test how well the snakes could hunt by either sense alone, the team put them in a tank with a clear bottom, through which they displayed a movie of cartoon fish swimming. The snakes struck at the fish accurately, suggesting they can capture prey using vision alone. They were then put with live fish in a pitch-black tank, and filmed with an infrared camera. Although the snakes struck out less often, they could “strike at and capture fish swimming several centimetres from the head and tentacles,” Catania says. He suggests the tentacles may enable snakes to catch prey at night or in murky waters (The Journal of Experimental Biology, DOI: 10.1242/jeb.039685). ASTEROIDS are known to have caused cataclysms on Earth – now it seems that Earth can hit back. Research led by Richard Binzel of the Massachusetts Institute of Technology shows that Earth’s gravity may cause landslides on asteroids that come within 100,000 kilometres of our planet, exposing fresh, underlying rock. This could explain why some asteroids that venture into the inner solar system are pale, while most others are stained a darker hue by the bombardment of space particles (Nature, DOI: 10.1038/ nature08709). The idea will be tested in 2029, when the asteroid Apophis is due to come within 40,000 kilometres of Earth. Binzel expects it to be resurfaced and change colour. Asteroids pale at the sight of Earth
Transcript of Earth's gravity makes asteroids go pale
14 | NewScientist | 23 January 2010
IS IT a bird, is it a plane? No, it’s a rock falling into a pool of water, but the jet of air it produces flies faster than a speeding bullet.
When an object such as a pebble drops into water, an air-filled cavity is created which ejects air at supersonic speeds, discovered Stephan Gekle at the University of Twente in the Netherlands, and colleagues.
Using high-speed photography,
the team spotted a cavity of air forming in an hourglass shape – with the top of the hourglass at the surface of the water and its base at the sinking object. To measure the speed of air rushing out upwards, they marked the air with smoke before the splash.
Even though their camera took 15,000 frames per second, they still couldn’t measure the fastest speeds directly, so they simulated
Pregnant drinking alters fetal DNA
DRINKING too much while pregnant chemically alters the fetus’s DNA and changes gene activity, a study in mice suggests.
When a pregnant woman drinks excessively, fetal alcohol syndrome can do permanent damage to her child. Suyinn Chong at the Queensland Institute of Medical Research in Herston, Australia, wondered whether “epigenetic” chemical changes to DNA – changes not in the genetic code itself but in the activity of certain genes – might be to blame.
Chong’s team bred mice with genes for brown and yellow fur that are known to be modified by epigenetics. The offspring of mothers that drank alcohol were brown more often than you would expect from their DNA alone, indicating that alcohol had altered fetal gene activity (PLoS Genetics, DOI: 10.1371/journal.pgen.1000811). These mice also weighed less and had smaller skulls.
Tentacled snakes can feel their way to a midnight feast
THE mysterious moustache of an aquatic snake may help
it “see” in murky waters by detecting subtle currents
generated by its prey.
Ken Catania and colleagues at Vanderbilt University in
Nashville, Tennessee, used a hair to deflect the upper-lip
tentacles of tentacled snakes (Erpeton tentaculatum), and
recorded the resulting nerve activity. The tentacles proved
to be exquisitely sensitive to even the tiniest deflection.
Mapping the path of the tentacle nerves showed that
they feed into an area of the brain that processes sensory
signals, close to where it responds strongly to visual
CH
RIS
MA
TT
ISO
N/
FL
PA
IN BRIEF
Little splash makes a supersonic air jet the behaviour they had observed. They found that shortly before the cavity closes, the pressure of the air at the bottom of the hourglass becomes higher relative to the “neck”. This difference pushes the air out at speeds faster than sound (Physical Review Letters, DOI: 10.1103/PhysRevLett.104.024501).
Jeffrey Aristoff of Princeton University is impressed by the research. The presence of supersonic flow was far from obvious, he says.
signals. “This suggests that [the snakes] are putting the
two parts of the information together,” Catania says.
To test how well the snakes could hunt by either sense
alone, the team put them in a tank with a clear bottom,
through which they displayed a movie of cartoon fish
swimming. The snakes struck at the fish accurately,
suggesting they can capture prey using vision alone.
They were then put with live fish in a pitch-black tank,
and filmed with an infrared camera. Although the snakes
struck out less often, they could “strike at and capture
fish swimming several centimetres from the head and
tentacles,” Catania says.
He suggests the tentacles may enable snakes to catch
prey at night or in murky waters (The Journal of
Experimental Biology, DOI: 10.1242/jeb.039685).
ASTEROIDS are known to have caused cataclysms on Earth – now it seems that Earth can hit back.
Research led by Richard Binzel of the Massachusetts Institute of Technology shows that Earth’s gravity may cause landslides on asteroids that come within 100,000 kilometres of our planet, exposing fresh, underlying rock. This could explain why some asteroids that venture into the inner solar system are pale, while most others are stained a darker hue by the bombardment of space particles (Nature, DOI: 10.1038/nature08709 ).
The idea will be tested in 2029, when the asteroid Apophis is due to come within 40,000 kilometres of Earth. Binzel expects it to be resurfaced and change colour.
Asteroids pale at the sight of Earth
