Parent volatiles in comet 9P/Tempel 1: before and after impact

We quantified eight parent volatiles (H2O, C2H6, HCN, CO, CH3OH, H2CO, C2H2, and CH4) in the Jupiter-family comet Tempel 1 using high-dispersion infrared spectroscopy in the wavelength range 2.8 to 5.0 micrometers. The abundance ratio for ethane was significantly higher after impact, whereas those for methanol and hydrogen cyanide were unchanged. The abundance ratios in the ejecta are similar to those for most Oort cloud comets, but methanol and acetylene are lower in Tempel 1 by a factor of about 2. These results suggest that the volatile ices in Tempel 1 and in most Oort cloud comets originated in a common region of the protoplanetary disk.     

Exposed water ice deposits on the surface of comet 9P/Tempel 1

We report the direct detection of solid water ice deposits exposed on the surface of comet 9P/Tempel 1, as observed by the Deep Impact mission. Three anomalously colored areas are shown to include water ice on the basis of their near-infrared spectra, which include diagnostic water ice absorptions at wavelengths of 1.5 and 2.0 micrometers. These absorptions are well modeled as a mixture of nearby non-ice regions and 3 to 6% water ice particles 10 to 50 micrometers in diameter. These particle sizes are larger than those ejected during the impact experiment, which suggests that the surface deposits are loose aggregates. The total area of exposed water ice is substantially less than that required to support the observed ambient outgassing from the comet, which likely has additional source regions below the surface.     

The dust grains from 9P/Tempel 1 before and after the encounter with Deep Impact

Gemini-N observed the properties of dust ejected from the nucleus of comet 9P/Tempel 1 before and after its encounter with Deep Impact. Marked changes were seen in the 7.8- to 13-micrometer spectral energy distribution and derived grain properties of the inner coma. A strong, broad silicate feature dominated by emission from amorphous pyroxene, amorphous olivine, and magnesium-rich crystalline olivine had developed by 1 hour after impact. The ejected dust mass is congruent with 10(4) to 10(6) kilograms on the basis of our models. Twenty-six hours later the silicate feature had faded, leaving a smooth featureless spectrum, similar to that observed before the impact, suggesting that the impact did not produce a new active region releasing small particles on the nucleus.     

Observations of comet 19P/Borrelly by the miniature integrated camera and spectrometer aboard Deep Space 1

The nucleus of the Jupiter-family comet 19P/Borrelly was closely observed by the Miniature Integrated Camera and Spectrometer aboard the Deep Space 1 spacecraft on 22 September 2001. The 8-kilometer-long body is highly variegated on a scale of 200 meters, exhibiting large albedo variations (0.01 to 0.03) and complex geologic relationships. Short-wavelength infrared spectra (1.3 to 2.6 micrometers) show a slope toward the red and a hot, dry surface (相似文献   

Impact features on Stardust: implications for comet 81P/Wild 2 dust

Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on the collector surfaces that were returned to Earth. The morphologies of these surprisingly diverse features were created by particles varying from dense mineral grains to loosely bound, polymineralic aggregates ranging from tens of nanometers to hundreds of micrometers in size. The cumulative size distribution of Wild 2 dust is shallower than that of comet Halley, yet steeper than that of comet Grigg-Skjellerup.     

Deep Impact: observations from a worldwide Earth-based campaign

On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics.     

Subaru telescope observations of Deep Impact

The impact cratering process on a comet is controversial but holds the key for interpreting observations of the Deep Impact collision with comet 9P/Tempel 1. Mid-infrared data from the Cooled Mid-Infrared Camera and Spectrometer (COMICS) of the Subaru Telescope indicate that the large-scale dust plume ejected by the impact contained a large mass (approximately 10(6) kilograms) of dust and formed two wings approximately +/-45 degrees from the symmetric center, both consistent with gravity as the primary control on the impact and its immediate aftermath. The dust distribution in the inner part of the plume, however, is inconsistent with a pure gravity control and implies that evaporation and expansion of volatiles accelerated dust.     

P/Halley: the quintessential comet

Halley's comet is the focus of an international scientific enterprise now under way. Ground-based astronomical observations are already yielding new information about the comet's nucleus and atmosphere. In the coming year, remote and in situ investigations from the ground, Earth orbit, Venus orbit, interplanetary space, and within the comet itself are expected to reveal much more. The climax of the enterprise will be the penetration of an armored European spacecraft into the center of the comet in March 1986.     

Deep Impact observations by OSIRIS onboard the Rosetta spacecraft

The OSIRIS cameras (optical, spectroscopic, and infrared remote imaging system) onboard the European Space Agency's Rosetta spacecraft observed comet 9P/Tempel 1 for 17 days continuously around the time of NASA's Deep Impact mission. The cyanide-to-water production ratio was slightly enhanced in the impact cloud, compared with that of normal comet activity. Dust particles were flowing outward in the coma at >160 meters per second, accelerated by the gas. The slope of the brightness increase showed a dip about 200 seconds after the impact. Dust Afrho values before and long after the impact confirm the slight decrease of cometary activity. The dust-to-water mass ratio was much larger than 1.     

深度学习训练数据 分布对植物病害识别的影响研究

牛结节性皮肤病（Lumpy Skin Disease,LSD）是一种由牛结节性皮肤病病毒（Lumpy Skin Disease Virus,LSDV）引起牛产生结节特征性病变的动物传染病,在东亚、南亚和东南亚等国家广泛流行,对当地养牛 业造成严重的经济损失。目前我国将 LSD 作为二类动物疫病管理,自 2019 年以来,国内已有 10 多个省份报告 过 LSD 疫情,疫情形势十分严峻。当前分离增殖 LSDV 较优的细胞为牛肾细胞。LSDV 为痘病毒科山羊痘病毒属, 其病毒粒子大小约为 290 nm × 270 nm,具有两种存在形态,病毒基因组复杂庞大,约为 151 kb,包含 150 多个 基因。目前 GenBank 数据库中仅保存有 40 多条 LSDV 病毒株的全基因组序列信息,流行毒株除了 田间野毒株, 近年来在亚洲部分地区还出现了田间野毒株和疫苗毒株的重组毒株,并且流行的重组毒株具有致病性,给未来 LSD 的疫苗研制和防控策略制定提出了新挑战。综述了 LSD 的病原学,以及非洲、欧洲和亚洲不同地区 LSDV 毒株全基因组学的研究进展,以期为 LSD 的防控和深入研究提供参考。     

Comet yanaka (1988r): a new class of carbon-poor comet

As part of a program to determine the chemical composition of a sample population of comets, a very unusual comet, Yanaka (1988r), was observed in January 1989. Although the comet showed the usual emissions of Ol and NH(2), it did not display any hint of C(2) or CN emission. The comet is depleted in C(2) by at least a factor of 100 and in CN by a factor of 25 relative to typical comets. If comets originate from interstellar clouds, Yanaka (1988r) could be an interloper from a cloud of different composition. If Yanaka (1988r) was formed within our solar system, the solar nebula was less uniform than assumed by most present models of formation.     

喀斯特深水水库叶绿素a与环境影响因子关系的研究——以阿哈水库为例

[目的]研究喀斯特深水水库叶绿素a与环境影响因子的关系。[方法]以阿哈水库为例,研究了2010年1~12月叶绿素a变量的变化及其与环境影响因子的关系,并采用修正的卡尔森营养状态指数对阿哈水库水质进行评价。[结果]阿哈水库水体叶绿素a含量在3~5和9月相对较高,6~8月相对较低,且具有明显的季节变化,其变化趋势为春季〉夏季〉秋季〉冬季;叶绿素a含量与透明度、溶解氧呈极显著相关（P〈0.01）,与氨氮呈显著相关（P〈0.05）;阿哈水库全年营养状态指数较高,除8、10和11月处于中营养化状态外,其他月份均处于富营养化状态。[结论]该研究为湖泊富营养化机理的研究提供了科学参考。