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Extraterrestrial dust reveals asteroid's past and future
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isas/jaxa
TALK about seeing a world in a grain of sand. The first sprinkling of asteroid dust brought to Earth by a spacecraft has revealed the space rock’s past – and likely future. When Japan’s Hayabusa probe landed on the 500-metre wide Itokawa (pictured), its equipment failed. It still collected dust, though, and limped back to Earth. Tomoki Nakamura of Tohoku University in Sendai and his colleagues have analysed the 1500 or so grains, all less than 0.2 millimetres across. They conclude that Itokawa was once part of a much larger asteroid. To form the minerals present in the samples, the space rock would have to have reached 800 °C. The decay of radioactive isotopes could have created that heat if the asteroid was 20 kilometres across. The samples hint at Itokawa’s future too. Some grains contain trapped noble gases, which get implanted by charged particles whizzing through space. From the levels and depths of these gases, Keisuke Nagao of the University of Tokyo and colleagues conclude that the grains had been on the asteroid’s surface for no more than 8 million years. Either Itokawa formed at that time, or it regularly but slowly loses material, exposing new layers in the process. In the second case, the asteroid may disappear in less than a billion years.
Electronic DNA analysis rules out anthrax attack WHEN a new strain of bacteria causes serious illness, being able to tell quickly whether it arose naturally or is the result of bioterrorism can be vital in devising the public health response. Now a DNA sequencing method that employs electronic sensing has been used to settle the question in a matter of hours rather than months. In June this year, a 39-year-old man was rushed to the Methodist Hospital in Houston, Texas, with swollen organs and struggling to breathe. Doctors feared the worst.
“The concern was that it was anthrax,” says James Musser, head of pathology at the hospital. Musser’s team used technology developed by Ion Torrent, based in Guilford, Connecticut, to identify the culprit as Bacillus cereus. Though closely related to B. anthracis, which causes anthrax, B. cereus produces severe infections only if it has gained a cluster of genes from the anthrax bacterium. But did Musser’s strain do so with the help of bioterrorists? The Ion Torrent technology
converts chemical signals from conventional DNA sequencing into electronic pulses that can be rapidly analysed by a microchip. Within a day, its results showed a lack of “genetic footprints” that might suggest a natural bacterium had been tampered with, says Musser (Archives of Pathology and Laboratory Medicine, in press). While the analysis couldn’t prevent this patient’s death, the technology was able to quickly rule out a deliberate attack. “This represents a new frontier in medicine,” he says. snorri gunnarson/getty
Asteroid’s future told in space dust
Sickness-free radiotherapy? RADIATION therapy to treat cancer is more effective in some people than others. A new discovery that reveals why could help to boost effectiveness of the therapy and reduce related radiation sickness. Vivian Cheung at the University of Pennsylvania in Philadelphia and colleagues exposed cells from 99 healthy individuals to a dose of radiation that prompts a cellular response similar to what happens during therapy. Following the dose, the activity of caspase – an “executioner” enzyme that causes cells to self destruct – increased by between 120 and 720 per cent, confirming that people respond differently to treatment. The team also looked at gene expression before and after exposure and identified 335 genes whose variation in expression correlated with caspase activity. Silencing five genes whose expression negatively correlated with caspase activity significantly increased cancer cells’ sensitivity to radiation (Genome Research, DOI: 10.1101/gr.122044.111). “Augmenting the sensitivity of cancer cells so that a lower dose of radiation can be given” could reduce side effects, says Cheung.
Moon’s shadow makes waves THE moon not only tugs at Earth’s oceans, it roils the atmosphere too. Four decades ago, theorists predicted that the moon’s shadow during an eclipse creates a dense pocket of cold gas that plows through the atmosphere like a boat, creating V-shaped waves. Attempts to measure them had failed – until now. In July 2009, during the longest eclipse calculated to occur in the coming century, Jann-Yenq Liu of the National Central University in Taiwan turned on a network of 1400 GPS receivers across Taiwan and Japan. Signals from GPS satellites ricochet
off ripples in the ionosphere – about 300 kilometres above ground – creating a time lag on their journey to the ground. Liu used computer programs to turn the lag into patterns that identify and locate the ripples. An eclipse shadow is thought to leave a unique ship-like signature, with bow waves and a wake. Liu says he saw both in the GPS signals (Geophysical Research Letters, DOI: 10.1029/2011gl048805). Richard Langley of the University of New Brunswick in Canada says the find is interesting but more research is needed to confirm it.
3 September 2011 | NewScientist | 19
isas/jaxa
TALK about seeing a world in a grain of sand. The first sprinkling of asteroid dust brought to Earth by a spacecraft has revealed the space rock’s past – and likely future. When Japan’s Hayabusa probe landed on the 500-metre wide Itokawa (pictured), its equipment failed. It still collected dust, though, and limped back to Earth. Tomoki Nakamura of Tohoku University in Sendai and his colleagues have analysed the 1500 or so grains, all less than 0.2 millimetres across. They conclude that Itokawa was once part of a much larger asteroid. To form the minerals present in the samples, the space rock would have to have reached 800 °C. The decay of radioactive isotopes could have created that heat if the asteroid was 20 kilometres across. The samples hint at Itokawa’s future too. Some grains contain trapped noble gases, which get implanted by charged particles whizzing through space. From the levels and depths of these gases, Keisuke Nagao of the University of Tokyo and colleagues conclude that the grains had been on the asteroid’s surface for no more than 8 million years. Either Itokawa formed at that time, or it regularly but slowly loses material, exposing new layers in the process. In the second case, the asteroid may disappear in less than a billion years.
Electronic DNA analysis rules out anthrax attack WHEN a new strain of bacteria causes serious illness, being able to tell quickly whether it arose naturally or is the result of bioterrorism can be vital in devising the public health response. Now a DNA sequencing method that employs electronic sensing has been used to settle the question in a matter of hours rather than months. In June this year, a 39-year-old man was rushed to the Methodist Hospital in Houston, Texas, with swollen organs and struggling to breathe. Doctors feared the worst.
“The concern was that it was anthrax,” says James Musser, head of pathology at the hospital. Musser’s team used technology developed by Ion Torrent, based in Guilford, Connecticut, to identify the culprit as Bacillus cereus. Though closely related to B. anthracis, which causes anthrax, B. cereus produces severe infections only if it has gained a cluster of genes from the anthrax bacterium. But did Musser’s strain do so with the help of bioterrorists? The Ion Torrent technology
converts chemical signals from conventional DNA sequencing into electronic pulses that can be rapidly analysed by a microchip. Within a day, its results showed a lack of “genetic footprints” that might suggest a natural bacterium had been tampered with, says Musser (Archives of Pathology and Laboratory Medicine, in press). While the analysis couldn’t prevent this patient’s death, the technology was able to quickly rule out a deliberate attack. “This represents a new frontier in medicine,” he says. snorri gunnarson/getty
Asteroid’s future told in space dust
Sickness-free radiotherapy? RADIATION therapy to treat cancer is more effective in some people than others. A new discovery that reveals why could help to boost effectiveness of the therapy and reduce related radiation sickness. Vivian Cheung at the University of Pennsylvania in Philadelphia and colleagues exposed cells from 99 healthy individuals to a dose of radiation that prompts a cellular response similar to what happens during therapy. Following the dose, the activity of caspase – an “executioner” enzyme that causes cells to self destruct – increased by between 120 and 720 per cent, confirming that people respond differently to treatment. The team also looked at gene expression before and after exposure and identified 335 genes whose variation in expression correlated with caspase activity. Silencing five genes whose expression negatively correlated with caspase activity significantly increased cancer cells’ sensitivity to radiation (Genome Research, DOI: 10.1101/gr.122044.111). “Augmenting the sensitivity of cancer cells so that a lower dose of radiation can be given” could reduce side effects, says Cheung.
Moon’s shadow makes waves THE moon not only tugs at Earth’s oceans, it roils the atmosphere too. Four decades ago, theorists predicted that the moon’s shadow during an eclipse creates a dense pocket of cold gas that plows through the atmosphere like a boat, creating V-shaped waves. Attempts to measure them had failed – until now. In July 2009, during the longest eclipse calculated to occur in the coming century, Jann-Yenq Liu of the National Central University in Taiwan turned on a network of 1400 GPS receivers across Taiwan and Japan. Signals from GPS satellites ricochet
off ripples in the ionosphere – about 300 kilometres above ground – creating a time lag on their journey to the ground. Liu used computer programs to turn the lag into patterns that identify and locate the ripples. An eclipse shadow is thought to leave a unique ship-like signature, with bow waves and a wake. Liu says he saw both in the GPS signals (Geophysical Research Letters, DOI: 10.1029/2011gl048805). Richard Langley of the University of New Brunswick in Canada says the find is interesting but more research is needed to confirm it.
3 September 2011 | NewScientist | 19