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Saturn's squeezes are pumping water from its geyser moon
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Space Science Institute/JPL/NASA
SATURN is steadily pumping water from its frozen moon Enceladus. Images taken by NASA’s Cassini probe support the idea that Saturn’s gravitational squeezing of the moon causes fissures to widen and contract, controlling how much icy material erupts from the cracks. Enceladus orbits Saturn in an elongated path, and changes in the strength of the giant planet’s tug create tidal stresses that squeeze and heat the moon’s interior. Ice geysers that erupt from the moon’s south pole (pictured, below) are thought to be fed by a briny subsurface ocean. These plumes sandblast other nearby moons and are probably the source of one of Saturn’s rings. Previous calculations had suggested that tidal stress could also be why the amount of material ejected in the plumes varies. To test the idea, Matt Hedman of Cornell University in Ithaca, New York, and his colleagues analysed seven years’ worth of Cassini data. Looking at the brightness of the plumes and adjusting for the viewing angle, the team found that geyser activity peaks when Enceladus is at its most distant point from Saturn (Nature, DOI: 10.1038/nature12371). That is when the moon experiences the strongest tensile stress, which probably widens the fissures and lets more material escape.
16 | NewScientist | 3 August 2013
Let’s stay together, darling… or the baby dies WHY stick with just one member of the opposite sex when there are so many to choose from? Love and tax breaks may be the reasons we cite today, but our primate ancestors had other motivations. Preventing a newborn from being killed by an unrelated male was top of the list. Social monogamy – when a male and female of the species stick together for life, although may mate with others – is rare in mammals generally. However, it occurs in over a quarter of primate species, including
humans, gibbons and New World monkeys such as titis. To investigate how pair bonding evolved, Kit Opie of University College London and colleagues studied the mating behaviour of 230 primate species. They selected behavioural traits associated with several possible evolutionary drivers, including protection from infanticide, the need for paternal care, and guarding females. Using data on the genetic links between the species, the team ran millions of computer simulations of the evolution of these traits
to work out which came first. All three were linked to the evolution of monogamy but only behaviours associated with protection from infanticide actually preceded it, suggesting that this was the driver (PNAS, DOI: 10.1073/pnas.1307903110). But others question whether the findings hold for humans. Carel van Schaik of the University of Zurich in Switzerland says it likely played a role but whether it was the driving force, as in nonhuman primates, “I think remains for now an open question”. Erica Olsen/FLPA
Saturn’s pumping its geyser moon
Natural booster for organ regeneration YOUR body naturally contains a chemical that can boost organ regeneration and speed up wound healing. Epoxyeicosatrienoic acids (EETs) help new blood vessels to form, so Dipak Panigrahy at Harvard Medical School in Boston and colleagues wondered whether they might also accelerate other types of growth. To find out, they injected mice with EETs straight after the surgical removal of a lung or part of their liver. Four days later, treated mice had 23 per cent more tissue growth in their remaining lung or 46 per cent more liver growth compared with mice that had received a placebo injection. Applying EETs to wounds in mice shortened healing time. The team also showed that EET concentrations in blood trebled in the week after human liver donors had undergone surgery (PNAS, DOI: 10.1073/pnas.1311565110). “This looks promising,” says Dan Weiss, who studies lung regeneration at the University of Vermont in Burlington. “EETs have been overlooked in regeneration schemes, so this might provide a window of opportunity.”
Get me a melon and make it snappy EVEN crocodiles need their five a day. At least half of all species of alligator and crocodile supplement their meaty diet with fruit. Reports that crocodiles have a taste for fruit go back decades, says Thomas Rainwater at the US Fish and Wildlife Service in Charleston, South Carolina. “But since these animals were long considered carnivores, no one paid much attention.” In a routine analysis of American alligators (Alligator mississippiensis) living in the Everglades National Park in Florida, Rainwater and colleagues found fruit including pond apples in
the alligators’ stomachs. They then turned up reports that at least 13 of the 23 living crocodilian species are fruit eaters (Journal of Zoology, doi.org/m9x). Whether or not crocodilians actively go after fruit is debatable: they might simply eat an animal that has itself recently dined on fruit. Catching them in the act is difficult as they hunt mainly at night, but there is some evidence that fruit is eaten deliberately. Last year, for example, a researcher working in south-east Asia reported seeing a wild Siamese crocodile tucking into a watermelon.
Space Science Institute/JPL/NASA
SATURN is steadily pumping water from its frozen moon Enceladus. Images taken by NASA’s Cassini probe support the idea that Saturn’s gravitational squeezing of the moon causes fissures to widen and contract, controlling how much icy material erupts from the cracks. Enceladus orbits Saturn in an elongated path, and changes in the strength of the giant planet’s tug create tidal stresses that squeeze and heat the moon’s interior. Ice geysers that erupt from the moon’s south pole (pictured, below) are thought to be fed by a briny subsurface ocean. These plumes sandblast other nearby moons and are probably the source of one of Saturn’s rings. Previous calculations had suggested that tidal stress could also be why the amount of material ejected in the plumes varies. To test the idea, Matt Hedman of Cornell University in Ithaca, New York, and his colleagues analysed seven years’ worth of Cassini data. Looking at the brightness of the plumes and adjusting for the viewing angle, the team found that geyser activity peaks when Enceladus is at its most distant point from Saturn (Nature, DOI: 10.1038/nature12371). That is when the moon experiences the strongest tensile stress, which probably widens the fissures and lets more material escape.
16 | NewScientist | 3 August 2013
Let’s stay together, darling… or the baby dies WHY stick with just one member of the opposite sex when there are so many to choose from? Love and tax breaks may be the reasons we cite today, but our primate ancestors had other motivations. Preventing a newborn from being killed by an unrelated male was top of the list. Social monogamy – when a male and female of the species stick together for life, although may mate with others – is rare in mammals generally. However, it occurs in over a quarter of primate species, including
humans, gibbons and New World monkeys such as titis. To investigate how pair bonding evolved, Kit Opie of University College London and colleagues studied the mating behaviour of 230 primate species. They selected behavioural traits associated with several possible evolutionary drivers, including protection from infanticide, the need for paternal care, and guarding females. Using data on the genetic links between the species, the team ran millions of computer simulations of the evolution of these traits
to work out which came first. All three were linked to the evolution of monogamy but only behaviours associated with protection from infanticide actually preceded it, suggesting that this was the driver (PNAS, DOI: 10.1073/pnas.1307903110). But others question whether the findings hold for humans. Carel van Schaik of the University of Zurich in Switzerland says it likely played a role but whether it was the driving force, as in nonhuman primates, “I think remains for now an open question”. Erica Olsen/FLPA
Saturn’s pumping its geyser moon
Natural booster for organ regeneration YOUR body naturally contains a chemical that can boost organ regeneration and speed up wound healing. Epoxyeicosatrienoic acids (EETs) help new blood vessels to form, so Dipak Panigrahy at Harvard Medical School in Boston and colleagues wondered whether they might also accelerate other types of growth. To find out, they injected mice with EETs straight after the surgical removal of a lung or part of their liver. Four days later, treated mice had 23 per cent more tissue growth in their remaining lung or 46 per cent more liver growth compared with mice that had received a placebo injection. Applying EETs to wounds in mice shortened healing time. The team also showed that EET concentrations in blood trebled in the week after human liver donors had undergone surgery (PNAS, DOI: 10.1073/pnas.1311565110). “This looks promising,” says Dan Weiss, who studies lung regeneration at the University of Vermont in Burlington. “EETs have been overlooked in regeneration schemes, so this might provide a window of opportunity.”
Get me a melon and make it snappy EVEN crocodiles need their five a day. At least half of all species of alligator and crocodile supplement their meaty diet with fruit. Reports that crocodiles have a taste for fruit go back decades, says Thomas Rainwater at the US Fish and Wildlife Service in Charleston, South Carolina. “But since these animals were long considered carnivores, no one paid much attention.” In a routine analysis of American alligators (Alligator mississippiensis) living in the Everglades National Park in Florida, Rainwater and colleagues found fruit including pond apples in
the alligators’ stomachs. They then turned up reports that at least 13 of the 23 living crocodilian species are fruit eaters (Journal of Zoology, doi.org/m9x). Whether or not crocodilians actively go after fruit is debatable: they might simply eat an animal that has itself recently dined on fruit. Catching them in the act is difficult as they hunt mainly at night, but there is some evidence that fruit is eaten deliberately. Last year, for example, a researcher working in south-east Asia reported seeing a wild Siamese crocodile tucking into a watermelon.