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首页> 外文期刊>Meteoritics & planetary science >Stardust Interstellar Preliminary Examination IX: High-speed interstellar dust analog capture in Stardust flight-spare aerogel
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Stardust Interstellar Preliminary Examination IX: High-speed interstellar dust analog capture in Stardust flight-spare aerogel

机译：星尘星际预备考试IX：星尘飞行备用气凝胶中的高速星际尘埃模拟物捕获

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The NASA Stardust mission used silica aerogel slabs to slowly decelerate and capture impinging cosmic dust particles for return to Earth. During this process, impact tracks are generated along the trajectory of the particle into the aerogel. It is believed that the morphology and dimensions of these tracks, together with the state of captured grains at track termini, may be linked to the size, velocity, and density of the impacting cosmic dust grain. Here, we present the results of laboratory hypervelocity impact experiments, during which cosmic dust analog particles (diameters of between 0.2 and 0.4 lm), composed of olivine, orthopyroxene, or an organic polymer, were accelerated onto Stardust flightspare low-density (approximately 0.01 g cm~(-3)) silica aerogel. The impact velocities (3-21 km s~(-1)) were chosen to simulate the range of velocities expected during Stardust’s interstellar dust (ISD) collection phases. Track lengths and widths, together with the success of particle capture, are analyzed as functions of impact velocity and particle composition, density, and size. Captured terminal particles from low-density organic projectiles become undetectable at lower velocities than those from similarly sized, denser mineral particles, which are still detectable (although substantially altered by the impact process) at 15 km s~(-1). The survival of these terminal particles, together with the track dimensions obtained during low impact speed capture of small grains in the laboratory, indicates that two of the three best Stardust candidate extraterrestrial grains were actually captured at speeds much lower than predicted. Track length and diameters are, in general, more sensitive to impact velocities than previously expected, which makes tracks of particles with diameters of 0.4 μm and below hard to identify at low capture speeds (<10 km s~(-1)). Therefore, although captured intact, the majority of the interstellar dust grains returned to Earth by Stardust remain to be found.
机译：NASA星尘任务使用二氧化硅气凝胶平板缓慢减速并捕获撞击中的宇宙尘埃颗粒，然后返回地球。在此过程中，沿着颗粒进入气凝胶的轨迹产生冲击轨迹。可以相信，这些轨道的形态和尺寸，以及在轨道终点处捕获的颗粒的状态，可能与撞击的宇宙尘埃颗粒的大小，速度和密度有关。在这里，我们介绍了实验室超高速撞击实验的结果，在此过程中，由橄榄石，邻二甲苯或有机聚合物组成的宇宙尘埃类似物粒子（直径在0.2到0.4 lm之间）被加速到星尘低密度（约0.01）上g cm〜（-3））二氧化硅气凝胶。选择撞击速度（3-21 km s〜（-1））来模拟星尘号星际尘埃（ISD）收集阶段预期的速度范围。分析轨道的长度和宽度，以及成功捕获粒子的过程，将其作为冲击速度和粒子组成，密度和尺寸的函数。从低密度有机弹丸中捕获的末端颗粒变得比在相同大小，密度更大的矿物颗粒中所捕获的颗粒低，但在15 km s〜（-1）仍可被检测到（尽管受到撞击过程的影响）。这些末端粒子的存活率，以及在实验室中以小速度低速捕获小颗粒时获得的轨道尺寸，表明实际上以比预期低得多的速度捕获了三个最佳星尘候选外星颗粒中的两个。通常，轨道长度和直径对撞击速度的敏感性比以前预期的要高，这使得直径为0.4μm及以下的粒子的轨道很难以低捕获速度（<10 km s〜（-1））识别。因此，尽管被完整捕获，但星尘返回地球的大多数星际尘埃颗粒仍待发现。

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