In the wee hours of Tuesday morning, 2009’s edition of the Leonid meteor shower will reach peak viewing time for sky-watchers in North America. Star gazers who lift their eyes to the heavens between 2 a.m. and 4 a.m. will likely be rewarded with a good show of “shooting stars.” A second, briefer, but very intense outburst is expected about 12 hours later — during the early-morning hours of November 18th in Asia [Sky & Telescope]. But that probably won’t last long enough for North Americans to see it when night returns here.
Like other meteor showers, such as the Perseids and the Orionids, the Leonids happen when Earth plows through a trail of debris left in the wake of a comet orbiting the sun [National Geographic News]. This comet, called Tempel-Tuttle, swings through the inner solar system about every 33 years, and last did so in 1998.
On special occasions we’ll pass directly through an unusually concentrated dust trail, or filament, which can spark a meteor storm resulting in thousands of meteors per hour. That indeed is what transpired in 1999, 2001 and 2002 [MSNBC]. This year won’t supply such a bonanza, astronomers predict, but we will see more meteors than average: probably 30 to 300 per hour, depending on where you are.
To get the most spectacular views, of course, you’ll have to venture away from city lights. But you won’t need to haul a telescope. For meteor showers, the naked eye is enough to enjoy the show.
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Image: iStockphoto
Tonight, in the wee hours, dedicated star watchers and people just looking for a good celestial show will turn their faces up to the heavens to watch the annual Orionid meteor shower. The Orionids are so named because the meteors appear to radiate from near the constellation Orion, aka the Hunter. This easily spotted constellation “kind of looks like an hourglass with a very recognizable belt of stars,” said astronomer Mark Hammergren [National Geographic News].
The “shooting stars” are really tiny fragments of debris left behind in space by Halley’s Comet, which loops through the inner solar system every 76 years and leaves a trail of dust in its wake. Most fragments are tiny, only about the size of a grain of sand–but they still go out in a blaze of glory as they vaporize in the Earth’s upper atmosphere. The best time to watch will be between 1 a.m. and dawn local time Wednesday morning, regardless of your location. That’s when the patch of Earth you are standing on is barreling headlong into space on Earth’s orbital track, and meteors get scooped up like bugs on a windshield [SPACE.com]. Tonight’s star gazers will benefit from a dark, moonless sky.
NASA scientist Bill Cooke says the Orionids have been strong in recent years. “Since 2006, the Orionids have been one of the best showers of the year, with counts of 60 or more meteors per hour” [SPACE.com].
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DISCOVER: 20 Things You Didn’t Know About… Meteors
Image: iStockphoto
Space aficionados are getting ready for the Perseid meteor shower, a show of shooting stars that occurs each year in the middle of August. This year, the event is expected to produce more shooting stars than usual; however, they may be slightly harder to see because of the moon’s unusual brightness due to the phase it will be in during the showers.
The Perseid Meteor Shower, which consists of debris from the Swift-Tuttle comet, became active on July 17, but have largely been so disperse and faint to see. [A] noticeable upswing in Perseid activity traditionally begins during the second week of August, leading up to their peak. They are typically fast, bright and occasionally leave persistent trains. And every once in a while, a Perseid fireball will blaze forth, bright enough to be quite spectacular and more than capable to attract attention even in bright moonlight [Space.com]. Like other meteor showers, Perseid’s fiery show is the result of particles disintegrating as they speed into the Earth’s atmosphere.
In other years, stargazers have been able to see up to 200 meteors per hour. But because the moon will be at last quarter the night of Aug. 13 and it will be at a rather bright waning gibbous phase a night or two earlier, seriously hampering observation of the peak of the Perseids, predicted to occur late on the nights of Aug. 11 and 12. [Space.com]. Still, although the moon’s brightness could hamper visibility, astronomers say the meteor shower should still be exciting to watch.
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The Mars rover Opportunity, an interloper on the Martian soil, has discovered another piece of metal that isn’t native to the planet: a boulder-sized iron meteorite that spun out of the sky and crashed into the planet sometime in the distant past. While the rock isn’t the first iron meteorite spotted on Mars (the two Mars rovers’ previous discoveries make this the fourth), it is the largest, measuring about 2 feet wide and 1 foot high. Researchers hope that studying the mega-meteorite will provide clues to the atmosphere and landscape that it encountered when it arrived on Mars.
Opportunity spotted the out-of-place object on July 18 and snapped a picture of it, but the rover was on its way towards a distant crater and didn’t stop. When NASA scientists saw the photographs, however, they ordered the rover to reverse course and head for the rock. “When you’re driving around on relatively smooth, flat, boring plains for a long time, anything that looks like a decent-sized rock says, ‘Come get me!’” says team member Albert Yen, a planetary scientist at NASA’s Jet Propulsion Laboratory [New Scientist].
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As of tomorrow, 101 years will have passed since the Tunguska Event, the mysterious explosion that flattened 800 square miles of Siberian forest. Just in time for the anniversary researchers have come up with yet another explanation for what may have caused the baffling blast. Previously, researchers best hypothesis was that a meteor struck the forest, but scientific expeditions failed to turn up an impact crater or any fragments of rock. The new hypothesis, which will be published in the journal Geophysical Research Letters, suggests that the Earth was hit by the icy core of a comet, which exploded in the atmosphere.
Researchers say that a comet strike would have released huge volumes of water vapour at very high altitude, creating highly reflective clouds that may explain why the sky was lit up for days after the collision, with people as far away as London saying that they could read newspapers outdoors at midnight, the scientists said [The Independent]. In an unusual twist, the evidence for the new theory comes from studies of the water vapor exhaust created by space shuttle launches.
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A shower of millions of rocks from space that collided with Mars, the Earth, and the moon about four billion years ago could have warmed our planet and made it wetter, say researchers. That’s what scientists found when they heated ancient rocks like those that hit the Earth billions of years ago and measured the carbon dioxide and water that was released, according to a study published in the journal Geochimica et Cosmochimica Acta.
Scientists have long suspected that the necessary materials for life could have come from outer space, and the study suggests how and when the Earth might have received these life-giving ingredients. During the 20-million-year-long meteor shower known as the Late Heavy Bombardment, the rocks that hurtled towards Earth would have been heated to extremely high temperatures as they entered the atmosphere. According to the scientists’ theory, the frictional heat of passing through the thin atmosphere that surrounded the Earth at that time would have been enough to strip the oxygen- and water-rich outer layers from the meteorites as they plunged toward the planet. That process would slowly have caused a buildup of oxygen and water in the atmosphere [Los Angeles Times]. At a rate of 20,000 degrees Celsius per second, the researchers heated samples of ancient rocks remaining from the bombardment in the absence of oxygen to prevent combustion. They then measured the gases released when the rocks were heated.
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Scientists say they have found fossils near the Colorado-New Mexico border that prove some dinosaurs survived the mass extinction that most researchers believe was caused by a meteor impact 65 million years ago. James Fassett, a scientist with the U.S. Geological Survey, says he has found evidence that a sizable population of ceratopsians and sauropods, a class of giant, dim-witted leaf-eaters such as the brachiosaurus, hung on for another 500,000 years in the [San Juan] basin. “There might even have been some T. rexes, based on some teeth we found” [Los Angeles Times], he said.
The bones of hadrosaurs, tyrannosaurs, anklyosaurs, and several other species were found together in a sandstone formation that dates to the Paleocene epoch—the time period after the so-called Cretaceous-Tertiary (K-T) extinction event, which is thought to have killed off the dinosaurs [National Geographic News]. To prove that the bones he found were indeed older than the extinction and eliminate the possibility that they had not simply been incorporated into newer rocks, Fassett points to his discovery of 34 bones from a single hadrosaur: If they had been washed away from their original location, they would almost certainly have been separated, not found together [Los Angeles Times].
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When the Messenger spacecraft swooped low past the planet Mercury on October 6 2008, it gathered up a wealth of data that will have planetary scientists puzzling for years. As researchers sort through findings regarding Mercury’s volcanic past, meteor impacts, and the effect of the solar wind on the innermost planet’s magnetosphere, one broad conclusion stands out: Mercury isn’t just a boring chunk of rock. Marilyn Lindstrom, a NASA program scientist, said the Messenger findings show that Mercury is “just an amazingly dynamic planet, both in the past and in the present” [Baltimore Sun].
Superficially, Mercury looks a lot like the moon: small, grayish-brown and pockmarked with craters. Some scientists assumed that Mercury’s surface formed the same way the moon’s did, with lighter rocks rising to the surface of a magma ocean and congealing into a brittle crust early on. But the new observations reveal that 40 percent of the surface was formed by volcanoes. “Up until before Messenger’s arrival, we weren’t even sure that volcanism existed on Mercury” [Wired], says researcher Brett Denevi. The presence of titanium oxide also suggests that the planet was hot enough in its first 100 million years to be covered in magma oceans.
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The enormous meteor that smashed into Mexico’s Yucatan peninsula 65 million years ago didn’t deal a death blow to the dinosaurs, a new study declares. Based on a close examination of sediment layers from that epoch, a team of researchers led by Gerta Keller has previously argued that the Chicxulub impact happened 300,000 years before the mass extinction known as the Cretaceous-Tertiary extinction event. Now, Keller has found supporting evidence that the impact had little immediate effect on the planet’s biome. Says Keller: “It didn’t kill the dinosaurs. In fact, it didn’t cause much damage that we can determine from the geological record” [The Scientist].
Since the 112-mile-wide Chicxulub crater was discovered in 1978, many researchers have come to believe that the massive impact caused clouds of dust to shroud the earth, cooling the planet and killing the dinosaurs along with many other species. But Keller’s new study, to be published in the Journal of the Geological Society, offers a serious challenge to that theory.
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They saw it coming, and they got what was coming to them. For the first time, researchers not only detected an asteroid in space, but also tracked its progress and then collected its debris after it crashed to Earth [Science News].
Astronomers won the space lottery last October when they spotted a small, car-sized asteroid headed straight for Earth 19 hours before it reached our planet, and were able to study it as it plunged towards the atmosphere. When the rock exploded about 23 miles above the Nubian Desert in northern Sudan, many astronomers thought that was the end of an already remarkable story. But researcher Peter Jenniskens decided to see if any fragments had reached the Earth’s surface, and joined forces with a team of Sudanese scientists and students to comb the desert.
Small asteroids like 2008 TC3 are fairly common, with about one asteroid impacting Earth each year. But these small asteroids are usually not spotted until they enter the Earth’s atmosphere. “It’s like when bugs splatter on the windshield. You don’t see the bug until it’s too late,” says physicist and study coauthor Mark Boslough [Science News]. Researchers got lucky with this asteroid–it was spotted by chance by an observatory in Arizona.
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Left-handed people may be in the minority, but left-handed amino acids rule the Earth. Researchers have long known that the building blocks of proteins can be constructed in either “left-handed” or “right-handed” versions that are mirror images of each other, but that almost every living organism on Earth uses left-handed amino acids. Now, a new study gives weight to a theory of how that preference came to pass. NASA researchers examined meteorites that predate the Earth’s formation, and say that those early rocks also have a preponderance of left-handed molecules. “Meteorites would have seeded the Earth with some of the prebiotic compounds like amino acids that are needed to get life started, and also biased the origin of life to the left-handed amino acid form,” says [study coauthor] Daniel Glavin [New Scientist].
Researchers note that if you make amino acids from scratch in a lab using their chemical components, you inevitably get half of the right-handed version and half of the left handed version. So it might be expected that if nature makes amino acids in space using similar chemistry, you’d also get a fifty-fifty mixture [CBC]. Yet that’s not what Glavin and his colleagues found when they studied the molecular deposits in six meteorites that are more than 4.5 billion years old. Instead, they found the ratio of amino acids tilted toward left-handedness in all six specimens. In one of the rocks, the imbalance was 18%, the largest ever reported for a meteorite. “I have to admit I didn’t believe it at first,” Glavin says [ScienceNOW Daily News].
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A tiny moon rock only two inches across that was picked up by one of the last astronauts to walk on the moon has given researchers new insight into the geological history of Earth’s satellite. The rock, scooped up during the Apollo 17 mission in 1972, is about 4.2 billion years old, and shows evidence that the moon once had a molten iron core that generated a magnetic field in the satellite’s early days. The findings are forcing researchers to rethink the prevailing notion that objects smaller than Mars can’t maintain a stable magnetic field.
Many of the rocks brought back from the Moon have a faint magnetic signal, suggesting that they originally cooled from magma when the Moon had a magnetic field. That was a surprise to many scientists who thought the Moon was too small and too cold to have ever possessed a geomagnetic dynamo where electric currents from the convection of molten iron generate a field [The New York Times]. But a molten core wasn’t the only explanation for the magnetic traces; some researchers thought that an intense bombardment of meteorites and asteroids created shocks that magnetized the rocks.
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Over 4 billion years ago the young and barren Earth was being buffeted by meteor strikes, and that violent bombardment could have created the first amino acids that then gave rise to the origin of life on the planet, a new study suggests. The hellish temperatures and pressures generated when an extraterrestrial object strikes Earth at speeds of several kilometers per second are enough to shatter and vaporize rock…. Yet part of such an immense burst of energy can trigger chemical reactions that generate complex organic substances from basic inorganic ingredients, says Takeshi Kakegawa [Science News].
Previously, researchers have suggested that organic molecules may have been created elsewhere in the universe and were brought to Earth by meteors. But the new study, in which researchers simulated the impact of meteorites in the primordial ocean, argues that the organic molecules could have been synthesized from the inorganic molecules already present on the planet when the meteorites crashed into the ocean. Other researchers have suggested similar processes for the creation of organic molecules on Earth, including lightning strikes or chemical reactions surrounding hot, volcanic vents in the deep sea.
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Yesterday, astronomers had the thrill of detecting an asteroid headed straight for earth and watching it hit our planet’s atmosphere just when they predicted, but without any of the panic that might be expected to accompany the foreknowledge of an asteroid strike. The space rock, which was about nine feet in diameter, was too small to do any damage, and burned up in the atmosphere while astronomers watched.
The object’s entry into the atmosphere wasn’t that unusual: Such an event happens roughly every three months. But this is “the first time we were able to discover and predict an impact before the event”, says Donald Yeomans, manager of NASA’s Near-Earth Object (NEO) programme [Nature News]. Researchers say the accurate prediction bodes well for humanity, for it suggests that astronomers are up to the challenge of detecting and tracking larger asteroids that could pose a more serious threat to human populations. Says Yeomans: “There are still a few kinks, a few processes that need to be smoother. But we passed this test” [Nature News].
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One hundred years ago today, a fireball streaked across the morning sky over Siberia and exploded, flattening the forest across an area of 830 square miles. The cause of the Tunguska Event, named for the nearby Tunguska River, has been a source of speculation ever since, with theories ranging from the absurd (space aliens!) to the most plausible: a disintegrating meteor exploding in the atmosphere. But a century after the event scientists still don’t have enough evidence to conclusively say what happened.
Scientists arrived at the most likely scenario, the meteor explosion, by studying the pattern of blasted trees; they concluded that an explosion hadn’t occurred at ground level, but rather four to six miles above the Earth’s surface. [T]he fragment, which is believed to have measured perhaps 100 feet across (although new research suggests it may have been even smaller), was probably traveling at around 21,000 miles per hour when it exploded…. Based on later assessments of the damage, the force of the blast was estimated to be between 10 and 15 megatons of TNT, roughly a thousand times more powerful than the atomic bomb that destroyed Hiroshima [Wired News].
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