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发布时间: 2025-05-30 05:16:16北京青年报社官方账号
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LOS ANGELES, May 12 (Xinhua) -- A subsurface ocean of molten or partially molten magma exists beneath the surface of Jupiter's volcanic moon Io, the Jet Propulsion Laboratory (JPL) said on Thursday."The finding heralds the first direct confirmation of this kind of magma layer at Io and explains why the moon is the most volcanic object known in the solar system," JPL said in a press release posted on its website.The finding was based on new data analysis from NASA's Galileo spacecraft, said JPL.The research was conducted by scientists at the University of California, Los Angeles; the University of California, Santa Cruz;, and the University of Michigan, Ann Arbor. The study is published this week in the journal Science, JPL said."Scientists are excited we finally understand where Io's magma is coming from and have an explanation for some of the mysterious signatures we saw in some of the Galileo's magnetic field data," said Krishan Khurana, lead author of the study and former co- investigator on Galileo's magnetometer team at UCLA."It turns out Io was continually giving off a 'sounding signal' in Jupiter's rotating magnetic field that matched what would be expected from molten or partially molten rocks deep beneath the surface."Io produces about 100 times more lava each year than all the volcanoes on Earth, according to data released by JPL in Pasadena, Los Angeles.While Earth's volcanoes occur in localized hotspots like the "Ring of Fire" around the Pacific Ocean, Io's volcanoes are distributed all over its surface, JPL said, adding that a global magma ocean about 30 to 50 km beneath Io's crust helps explain the moon's activity."It has been suggested that both the Earth and its moon may have had similar magma oceans billions of years ago at the time of their formation, but they have long since cooled," said Torrence Johnson, a former Galileo project scientist based at JPL, an affiliation with NASA."Io's volcanism informs us how volcanoes work and provides a window in time to styles of volcanic activity that may have occurred on the Earth and moon during their earliest history," said Johnson, who was not directly involved in the study.NASA's Voyager spacecraft discovered Io's volcanoes in 1979, making that moon the only body in the solar system other than Earth known to have active magma volcanoes. The energy for the volcanic activity comes from the squeezing and stretching of the moon by Jupiter's gravity as Io orbits the largest planet in the solar system.Galileo was launched in 1989 and began orbiting Jupiter in 1995. Unexplained signatures appeared in magnetic field data from Galileo flybys of Io in October 1999 and February 2000. After a successful mission, the spacecraft was intentionally sent into Jupiter's atmosphere in 2003.

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LOS ANGELES, April 18 (Xinhua) -- Sugarcane has the effect of cooling temperatures, thus playing role in stemming global warming, a new study has found.Sugarcane does so by reflecting sunlight back into space and by lowering the temperature of the surrounding air as the plants " exhale" cooler water, according to the study conducted by researchers at the Carnegie Institution's Department of Global Ecology.The researchers used data from hundreds of satellite images over 733,000 square miles (about 1,173 square kilometers) in Brazil, where sugarcane is widely grown. They measured temperature, reflectivity (also called albedo), and evapotranspiration -- the water loss from the soil and from plants as they exhale water vapor.The findings showed that expansion of sugarcane in areas previously occupied by other Brazilian crops cools the local climate.Converting from natural vegetation to crop/pasture on average warmed the cerrado by 2.79 Fahrenheit (1.55 Centigrade, but that subsequent conversion to sugarcane, on average, cooled the surrounding air by 1.67 Fahrenheit (0.93 Centigrade), the researchers said in the study published in the April issue of Nature Climate Change."We found that shifting from natural vegetation to crops or pasture results in local warming because the plants give off less beneficial water. But the bamboo-like sugarcane is more reflective and gives off more water -- much like the natural vegetation," said lead researcher Scott Loarie. "It's a potential win-win for the climate -- using sugarcane to power vehicles reduces carbon emissions, while growing it lowers the local air temperature."Brazilians are world leaders in using biofuels for gasoline. About a quarter of their automobile fuel consumption comes from sugarcane, which significantly reduces carbon dioxide emissions that otherwise would be emitted from using gasoline.The researchers emphasized that the beneficial effects are contingent on the fact sugarcane is grown on areas previously occupied by crops or pastureland, and not in areas converted from natural vegetation. It is also important that other crops and pastureland do not move to natural vegetation areas, which would contribute to deforestation.So far most of the thinking about ecosystem effects on climate considers only impacts from greenhouse gas emissions. But according to co-researcher Greg Asner, "It's becoming increasingly clear that direct climate effects on local climate from land-use decisions constitute significant impacts that need to be considered core elements of human-caused climate change."

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BEIJING, April 12 (Xinhuanet) -- The elderly have a difficult time with multi-tasking as a study suggests that older brains behave differently when it comes to switching between two tasks, according to media reports on Tuesday.Researchers used functional magnetic resonance imaging (FMRI) to analyze brain activity in 20 people over age 60 by asking them to contemplate outdoor photos shown briefly. Then the elderly were presented with the picture of a face and asked to determine its gender and age, before being asked to recall details from the original scene they viewed.Researchers then compared their results to a similar experiment with 20 younger adults and found the brains of older subjects were less capable of disengaging from the interruption and reestablishing the neural connections necessary to switch back to focusing on the original memory."Unlike younger individuals, older adults failed to both disengage from the interruption and re-establish functional connections associated with the disrupted memory network," write Wesley C. Clapp of the University of California, San Francisco, and colleagues in the Proceedings of the National Academy of Sciences.The study, published in the online edition of the journal Proceedings of the National Academy of Sciences, sheds new lights into a growing body of studies showing that one's ability to move from one task to another in quick succession becomes more difficult with age.

  

BEIJING, March 29 (Xinhuanet) -- A new study has found that rejection can literally hurt in the same way as physical pain does, according to media reports Tuesday.Researchers found that intense emotional pain, such as feelings of rejection after a breakup of a relationship, can trigger brain activities similar to when people suffer physical pain.The research findings were published in Tuesday's Proceedings of the National Academy of Sciences.The study followed 40 volunteers who experienced unwanted romantic breakups in the past six months, and the researchers analyzed their brain activity during two "painful" situations.The results showed that the two situations, thinking about the loss of their ex-partner and experiencing mild physical pain similar to holding a very hot coffee cup, caused response in the overlapping parts of the brain."This tells us how serious rejection can be sometimes," said study author Edward E. Smith, director of cognitive neuroscience at Columbia University. Smith added. "Our ultimate goal is to see what kind of therapeutic approach might be useful in relieving the pain of rejection."

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