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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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