ScienceShots from science online
Shine a light. Galactic centers are usually hidden by so much dust and gas that they're difficult to probe. But a powerful x-ray burst, represented in orange in this artist's rendering, should provide new insights. The flare erupted after a supermassive black hole bit into an errant star that moved too close for comfort, and the burst in turn heated up and illuminated nearby galactic material (purple). That gave astronomers a rare look at the structure and chemical composition of the galaxy's heart, they report in the 1 May issue of The Astrophysical Journal Letters, a view that may shed literal light on how galaxies evolve. (Image: MPE/ESA)
Bat breath. Does alcohol cloud bats' judgment? When given the choice between an ethanol-based nectar containing sucrose and one containing fructose, the animals preferred the former. That may not be the wisest decision, as fructose helps them metabolize alcohol faster, say researchers, who report the results of a bat breathalyzer test online 18 April in the Journal of Experimental Biology. Because ripe fruits contain ethanol and a variety of different sugars, such cloudy judgment could affect which fruits bats eat--and hence which seeds they disperse--in the wild
Two for tea. A rose with any other gene ... would not smell as sweet. Tea roses emit an earthy, spicy fragrance composed mainly of the compound 3,5-dimethoxytoluene (DMT). Two enzymes are needed to make DMT, and tea roses and their hybrid descendants are the only roses that have the genes for both. Reporting online 15 April in the Proceedings of the National Academy of Sciences, researchers say the gene for the second enzyme in tea roses probably started out as a duplication of the first. Eventually, simple mutations in the extra copy gave the plant the ability to make DMT and sweeten many a bouquet.
Ultimate ancestor. This innocuous-looking comb jelly might just be the direct progeny of the first animal on Earth. A massive analysis of the evolutionary biology of animals suggests that the earliest member of the kingdom that includes insects, fish, reptiles, birds, mammals, and humans--plus a host of others--was related to the comb jelly. That's a major surprise, a team reports in the 10 April issue of Nature, because the jelly possesses distinct tissues and a nervous system, whereas the previous candidate for the planet's first true animal, the sponge, lacks both. The discovery is a blow to the mindset that evolution automatically means increasing complexity, say the researchers. (Photo: Casey Dunn)
Tiny tempest. Physicists have replicated Jupiter's stormy weather in soap bubbles. There's even a miniature equivalent of the Great Red Spot. The trick has to do with a process known as thermal convection, or the transfer of heat within fluid systems. The researchers report in the 7 April issue of Physical Review Letters that when they heated the bubbles at their equators and cooled them at their poles, the resulting dynamics closely resembled convection patterns on Jupiter's surface. The stormy bubbles could shed light on similar dynamics in Earth's atmosphere and deep beneath its surface. They're also just neat to watch.
Breathless. Scientists have identified the first known lungless frog in the Indonesian region of Borneo. The amphibian, commonly known as the Bornean Flat-headed frog (Barbourula kalimantanensis), was first discovered in the 1970s, but scientists didn't know it was lungless until they autopsied it in the field. The frog draws air through its skin, and the absence of lungs may allow it to sink to the bottom of the frigid, fast-flowing waters in which it lives. Although there are several other lungless amphibians, including some salamanders, lunglessness is a rare evolutionary trait that has probably occurred only three times, the team reports online 17 April in Current Biology.
Paddle on. Many species of aquatic snakes propel themselves with flat, paddlelike tails. How did such tails evolve? Researchers recently devised a novel method to find out: They attached various sizes of fake paddles to tiger snakes, which are mostly terrestrial. The larger paddles didn't work so well, but the smaller paddles allowed the snakes to swim 25% faster than usual--although the paddles slowed the snakes’ slithering on land by 17%. That kind of advantage might have been enough to encourage the snakes, bit by bit, to commit to the water, the authors suggest in April's issue of Functional Ecology.
Common gold. Nearly all of the gold artifacts found by archaeologists in the Americas have come from the treasure troves of ancient kings. But not this necklace of gold and turquoise. The necklace apparently was fashioned from gold deposits near Lake Titicaca, Peru, by hunter-gatherers who were settling down to subsistence farming. The necklace was found with the bones of its wearer, which lacked royal accoutrements, so the researchers suspect that he was a local big shot but probably not a king. Made an estimated 3700 to 4000 years ago, it's the oldest gold object ever found in the Western Hemisphere, researchers report online this week in the Proceedings of the National Academy of Sciences.
Crunchy calamari. The Humboldt squid (Dosidicus gigas) should have a big problem at mealtime. It dispatches its prey with a sharp beak that resembles a parrot's bill, yet unlike a parrot, the squid has no skeleton to anchor its bite. So why doesn't the ultra-hard beak tear into the squid's soft flesh as it eats? The answer, researchers report in the 28 March issue of Science, is that the base of the beak is 100 times more pliable than the pointy tip. The gradient is governed by protein and water concentrations in the beak--a trick engineers hope they can someday mimic to ease boundaries between hard and soft materials such as those in prosthetics. (Image: © 2008 Science)
Showoffs. Amazon River dolphins toss and thrash clumps of leaves, sticks, and even rocks. They're not just playing: Researchers say it's the first example of an aquatic mammal using props for sexual display. In more than 6000 dolphin sightings, observers spied 221 instances of prop-carrying, mostly by adult males. The behavior was most common near adult females and was especially frequent in July, 14 months before most females bear their young, the team reports online 25 March in Biology Letters. (No one knows exactly how long Amazon dolphins gestate their young, but other dolphins and small whales take 11 to 15 months
Blinding light. This innocuous-looking fireball is the brightest object ever spied from Earth. What you're seeing is the afterglow of a gamma-ray burst, the most powerful type of explosion in the universe, captured by NASA's Swift satellite on 19 March. Billions of years before our planet formed, a giant star exploded--or two black holes collided--in the direction of the constellation Boötes, releasing titanic amounts of energy. How bright was it? Astronomers estimate the object was 2.5 million times more luminous than the brightest supernova recorded so far--and billions of times brighter than our sun. That made it radiant enough to been seen with the naked eye despite its vast distance of some 7.5 billion light-years. Zap! Call it supercharged static electricity. This image, taken by the Hubble Space Telescope in ultraviolet light, shows auroras encircling Jupiter's north pole. On Earth, auroras, or Northern Lights, occur when the planet's magnetic field traps particles in the solar wind, causing them to fluoresce. Something different happens on Jupiter. Its close-orbiting moon Io boasts its own magnetic field, which blocks the flow of electrically charged solar particles whipping through Jupiter's magnetosphere. Every so often, enough charge builds up to send waves of glowing plasma blasting 400,000 kilometers or more back into Jupiter's upper atmosphere, researchers report 15 March in Geophysical Research Letters. Cue the light show. (Photo: LPAL/ Université de Liège)
Trinket. Cheapskates take note: Researchers have fashioned the smallest ever diamond ring. Australian physicists used a laser to carve the gem--a simple band 5 millionths of a meter wide and 300 billionths of a meter thick--from a much larger, artificial diamond. As they reported this week at the annual meeting of the American Physical Society in New Orleans, Louisiana, the researchers designed the ring to capture and process individual photons as part of a device called a quantum computer, which would operate thousands of times faster than today's best microprocessors.

New method evaluates past meteorite strikes from changes
in sea chemistry

Ancient meteorite impacts can be detected from minute changes in the composition of sea water, according to American researchers.

By analysing changes in the ratio of osmium isotopes you can work out the timings of past impacts of stony meteorites called chondrites. What's more, you can also tell how large these impacts were, claims François Paquay of the University of Hawaii, Honolulu.

Paquay and his colleagues used the method to study known impacts, including the blast thought to have wiped out the dinosaurs 65 million years ago, and another one thought to have hit Earth some 35 million years ago. As the team reports in Science ¹, the chemicals of seabed sediments can give an indication of the size of what hit us.

Indirect estimates

The new method produces estimates that are substantially different from those based on crater sizes, Paquay’s team admits. But they argue that the new method has substantial advantages over previous techniques. If the new method is correct, it could mean revising the estimated sizes of several past blasts.

“We do not need a preserved impact crater,” explains Paquay. “We just need a site or two with well-preserved and well-dated deep marine sediments, as the osmium isotopes are well mixed in the global ocean.”

Because the new method does not study impact craters directly, it could identify impacts that have so far gone undetected. “We do hope to find unrecognized impact events, especially deep-ocean impact events, as 70% of Earth’s surface is made of water,” says Paquay.

Normally, sea water has a high ratio of osmium-187 to osmium-188. Chondrite meteorites, which represent roughly 80% of known impacts, according to Paquay, generally have a lower ratio. When a large meteorite hits and vaporizes and its osmium ends up in the sea, this will alter the ratio of isotopes left behind in the sea.

How far back it will be possible to go is up for debate.

“It’s an interesting and new method to arrive at such numbers,” says Christian Köberl, head of the Department of Lithospheric Studies at the University of Vienna, Austria. “I am a little more sceptical, though, that too many impacts will be studied that way, because the osmium isotopic signal in the oceans only goes back maybe 100 million years, and there are not too many large impacts during that time period besides the two already studied by Paquay et al .”

Does size matter?

Previously, the diameter of impacting meteorites has been estimated in two ways. The first involves looking at iridium levels around the world. Iridium is relatively scarce naturally, so relatively large amounts of it in a soil layer can indicate a big rock smashing into Earth.

The second method involves modelling the impact, mainly on the basis of the size of the crater.

“Each of those methods has its problems,” says Köberl.

With the iridium method you have to assume the element is distributed homogeneously around the world, he explains, and you have to know what type of meteorite it was. You also need to assume no iridium has been removed since it was deposited.

For impact simulations, he says, the variety of velocities and angles involved means that estimated diameters can sometimes be wrong by a factor of three.

One problem in evaluating the new method is that, as estimated in the cases investigated in the new paper, the different methods don’t all give the same answer.

While Paquay’s osmium estimates are similar to those arrived at from iridium data, they differ substantially from those generated using impact simulations.

For example, for the Late Eocene ‘Popigai’ impact, his 3-kilometre diameter for the meteorite is roughly similar to the 4-kilometre estimate from the iridium method, but it is some way off the 8 kilometres given by impact simulations.

If the impact simulations are correct, it means that more than 90% of the osmium and iridium carried by these projectiles remains hidden somewhere in the Earth system,” Paquay says. “We think that this is unlikely, but we can’t rule this possibility out without additional work.”

A major problem with the osmium method is the number of uncertainties involved, says Graham Pearson, an expert in isotope geochemistry at Durham University, UK. These include not only exactly what the ratio of isotopes in any given meteorite actually is, but also how much osmium actually ends up in the sea.

“It [the paper] is a nice illustration of the potential of finding even very small impacts in the stratigraphic record. I’m kind of worried their estimates differ so much from the ballistic estimates,” says Pearson.

From Nature News

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