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Radiation didn't wipe out the dinosaurs
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NASA
In brief– Stressed in space
Moon’s gentle surface might keep ancient treasure intact ADD this to the reasons why we need to revisit the moon: it may be the best place to find the earliest evidence of life on Earth. Yes, it sounds perverse, says Ian Crawford of Birkbeck, University of London, but conditions on the lunar surface are much more gentle than those on Earth, so meteorites that blasted off our planet billions of years ago may well still be lying around on the moon. What no one knew, however, was whether Earth rocks were likely to have survived the impact. To find out, Crawford and colleague Emily Baldwin used a method of
simulating impacts called a hydrocode. They calculated what would happen to meteors hitting the moon at a range of impact angles at up to 5 kilometres per second. “Terrestrial meteorites have a good chance of survival, especially those hitting the moon at relatively low velocities and at shallow angles,” says Crawford, who presented his results, submitted to the journal Astrobiology, at the British Association for the Advancement of Science meeting in York last week. Some 4 billion years ago, comets and asteroids colliding with Earth kicked up a lot of rocks, many of which would have found their way to the moon. “We might be able to find rocks that reveal the conditions under which life arose on our planet,” says Crawford.
Radiation cleared of killing dinosaurs WE CAN scratch a couple of suspects from the list of possible dinosaur killers. Too few dinosaur fossils show evidence of bone cancer to conclude that a lethal dose of ionising radiation did them in – or that they took up smoking, as Gary Larson once whimsically suggested in a Far Side cartoon. Adrian Melott, an astrobiologist at the University of Kansas in www.newscientist.com
Lawrence, has suggested that periodic overdoses of cosmic rays or bursts of gamma rays might have caused mass extinctions. Past periods of heavy radiation leave little direct trace, but cancers induced by cosmic rays could have spread to bones. So Melott turned to data collected by his colleague Bruce Rothschild on signs of cancer in the fossilised bones of 708
dinosaurs. When they compared the incidence of bone cancer with that in today’s birds and reptiles, they found no evidence for elevated cancer rates in dinosaurs (www.arxiv.org/abs/0704.1912). However, Melott is going to keep looking. He says the results for hadrosaurs, which lived during the final 5 million years of the dinosaurs’ reign, are intriguing. Hadrosaurs had the only case of bone cancer and the only cases of benign abnormalities called haemangiomas.
“HOUSTON, we’ve had a problem” was the famous understatement by astronaut James Lovell after an explosion on board Apollo 13 that might have doomed its crew to die in space. Now a team led by Jennifer Boyd of the University of California, San Francisco, has found that the way astronauts react to stress varies between cultures. They analysed weekly mood questionnaires completed by eight US astronauts and nine Russian cosmonauts on board the International Space Station. While the Russians tended to experience depression in combination with fatigue, US astronauts experienced depression linked to anxiety. Understanding different cultural responses to stress is crucial, the authors write, “because they have the potential to seriously disrupt future international space missions” (Acta Astronautica, DOI: 10.1016/ j.actaastro.2006.12.002).
Dark matter gets a warm makeover DARK matter may be “warm” – made of fast, lightweight particles – contrary to the most widely accepted theory. Liang Gao and Tom Theuns of the University of Durham, UK, modelled the behaviour of candidate dark matter particles, both warm and “cold” – made of slow-moving, heavy particles. Cold dark matter coalesces into blobs, they found, while warm dark matter develops chaotically, into filaments. Small, slowburning stars could form in these filaments, without forming heavy elements, and a few could still be shining (Science, vol 317, p 1527). That fits with the discovery of ancient small stars in the Milky Way that are very low in heavy elements. “It is suggestive that dark matter is warm,” Theuns says. 22 September 2007 | NewScientist | 19
NASA
In brief– Stressed in space
Moon’s gentle surface might keep ancient treasure intact ADD this to the reasons why we need to revisit the moon: it may be the best place to find the earliest evidence of life on Earth. Yes, it sounds perverse, says Ian Crawford of Birkbeck, University of London, but conditions on the lunar surface are much more gentle than those on Earth, so meteorites that blasted off our planet billions of years ago may well still be lying around on the moon. What no one knew, however, was whether Earth rocks were likely to have survived the impact. To find out, Crawford and colleague Emily Baldwin used a method of
simulating impacts called a hydrocode. They calculated what would happen to meteors hitting the moon at a range of impact angles at up to 5 kilometres per second. “Terrestrial meteorites have a good chance of survival, especially those hitting the moon at relatively low velocities and at shallow angles,” says Crawford, who presented his results, submitted to the journal Astrobiology, at the British Association for the Advancement of Science meeting in York last week. Some 4 billion years ago, comets and asteroids colliding with Earth kicked up a lot of rocks, many of which would have found their way to the moon. “We might be able to find rocks that reveal the conditions under which life arose on our planet,” says Crawford.
Radiation cleared of killing dinosaurs WE CAN scratch a couple of suspects from the list of possible dinosaur killers. Too few dinosaur fossils show evidence of bone cancer to conclude that a lethal dose of ionising radiation did them in – or that they took up smoking, as Gary Larson once whimsically suggested in a Far Side cartoon. Adrian Melott, an astrobiologist at the University of Kansas in www.newscientist.com
Lawrence, has suggested that periodic overdoses of cosmic rays or bursts of gamma rays might have caused mass extinctions. Past periods of heavy radiation leave little direct trace, but cancers induced by cosmic rays could have spread to bones. So Melott turned to data collected by his colleague Bruce Rothschild on signs of cancer in the fossilised bones of 708
dinosaurs. When they compared the incidence of bone cancer with that in today’s birds and reptiles, they found no evidence for elevated cancer rates in dinosaurs (www.arxiv.org/abs/0704.1912). However, Melott is going to keep looking. He says the results for hadrosaurs, which lived during the final 5 million years of the dinosaurs’ reign, are intriguing. Hadrosaurs had the only case of bone cancer and the only cases of benign abnormalities called haemangiomas.
“HOUSTON, we’ve had a problem” was the famous understatement by astronaut James Lovell after an explosion on board Apollo 13 that might have doomed its crew to die in space. Now a team led by Jennifer Boyd of the University of California, San Francisco, has found that the way astronauts react to stress varies between cultures. They analysed weekly mood questionnaires completed by eight US astronauts and nine Russian cosmonauts on board the International Space Station. While the Russians tended to experience depression in combination with fatigue, US astronauts experienced depression linked to anxiety. Understanding different cultural responses to stress is crucial, the authors write, “because they have the potential to seriously disrupt future international space missions” (Acta Astronautica, DOI: 10.1016/ j.actaastro.2006.12.002).
Dark matter gets a warm makeover DARK matter may be “warm” – made of fast, lightweight particles – contrary to the most widely accepted theory. Liang Gao and Tom Theuns of the University of Durham, UK, modelled the behaviour of candidate dark matter particles, both warm and “cold” – made of slow-moving, heavy particles. Cold dark matter coalesces into blobs, they found, while warm dark matter develops chaotically, into filaments. Small, slowburning stars could form in these filaments, without forming heavy elements, and a few could still be shining (Science, vol 317, p 1527). That fits with the discovery of ancient small stars in the Milky Way that are very low in heavy elements. “It is suggestive that dark matter is warm,” Theuns says. 22 September 2007 | NewScientist | 19