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首頁> 外文學(xué)位 >Recognizing impact glass on Mars using surface texture, mechanical properties, and mid-infrared spectroscopic methods.
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Recognizing impact glass on Mars using surface texture, mechanical properties, and mid-infrared spectroscopic methods.

機(jī)譯：使用表面紋理，機(jī)械性能和中紅外光譜法識(shí)別火星上的撞擊玻璃。

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A primary goal of future Mars sample return missions is to obtain samples whose isotopic ages can be used to place absolute time constraints on the relative Martian crater chronology. Thus, identifying the origin of surface material as impact or volcanic prior to its return to Earth will be critical. This dissertation focuses on four strategies for identifying and characterizing impact melt breccias from both landed and orbital perspectives. In Part 1, the geology of Viking 2 Landing (VL2) site is re-evaluated using recently acquired orbital data. Measurements of relict landform topography indicate that a layer of sedimentary material at least 120 m thick has been eroded from the site. Crater counts indicate an extreme deficiency of small-diameter craters (500 m), indicating that resurfacing has continued up to the present. Thermal inertia data over the site is consistent with some rocks being impact-emplaced and possibly impact-derived. In Part 2, three textural characteristics were identified as potential discriminants between vesicular impact and volcanic glasses: vesicle shape (elongation), orientation, and spatial density. Additionally, a theoretical model was developed to constrain the conditions necessary for the preservation of deformed bubble textures. The results suggest that deformed bubbles are unlikely to be preserved in typical Martian basalts or basaltic andesites. Part 3 is an endeavor to extract science from mission support operations. First, a method for determining the bulk density of rocks via a pushing (i.e., by a robotic spacecraft arm) was developed and applied to VL2 rock-pushing data. Although the large measurement uncertainties preclude drawing firm conclusions, the results demonstrate the feasibility of the technique. Second, results from the Rock Abrasion Tool (RAT) on the Spirit rover were analyzed to infer the mechanical strength of ground surfaces. Rocks in the Columbia Hills were found to be mechanically consistent with impact melt breccias. In Part 4, systematic variations in glass mid-infrared reststrahlen band positions were determined with variations in glass chemistry, degree of crystallinity, and quench rate. Results indicate that the spectra of rapidly quenched glasses with a high fictive temperature exhibit shifts to shorter wavelengths, causing them to appear more silica-rich.
機(jī)譯：未來火星樣本返回任務(wù)的主要目標(biāo)是獲得其同位素年齡可用于在相對(duì)火星隕石坑年代學(xué)上施加絕對(duì)時(shí)間限制的樣本。因此，在返回地面之前將表面物質(zhì)的起源識(shí)別為撞擊或火山是至關(guān)重要的。本文著眼于從著陸和軌道角度識(shí)別和表征撞擊熔巖角礫巖的四種策略。在第1部分中，使用最近獲取的軌道數(shù)據(jù)重新評(píng)估了維京2號(hào)著陸點(diǎn)（VL2）的地質(zhì)情況。對(duì)遺跡地貌地形的測(cè)量表明，至少有120 m厚的沉積物質(zhì)層已從該地點(diǎn)侵蝕。隕石坑的數(shù)量表明小直徑隕石坑（<500 m）的極端缺乏，表明直到現(xiàn)在，堆焊工作仍在繼續(xù)。場(chǎng)地上的熱慣性數(shù)據(jù)與某些巖石被撞擊并可能來源于撞擊一致。在第2部分中，確定了三個(gè)紋理特征作為區(qū)分囊泡撞擊和火山玻璃的潛在特征：囊泡形狀（伸長(zhǎng)率），方向和空間密度。此外，開發(fā)了一個(gè)理論模型來約束保存變形氣泡紋理所需的條件。結(jié)果表明，變形的氣泡不太可能在典型的火星玄武巖或玄武質(zhì)安山巖中保留。第三部分是從任務(wù)支持操作中提取科學(xué)的努力。首先，開發(fā)了一種用于通過推動(dòng)（即，通過自動(dòng)航天器臂）確定巖石的堆密度的方法，并將其應(yīng)用于VL2推巖數(shù)據(jù)。盡管較大的測(cè)量不確定性無法得出明確的結(jié)論，但結(jié)果證明了該技術(shù)的可行性。其次，分析了Spirit流動(dòng)站上的巖石磨損工具（RAT）的結(jié)果，以推斷出地面的機(jī)械強(qiáng)度。發(fā)現(xiàn)哥倫比亞山的巖石在機(jī)械上與沖擊熔融角礫巖一致。在第4部分中，通過玻璃化學(xué)性質(zhì)，結(jié)晶度和淬滅速率的變化確定了玻璃中紅外reststrahlen帶位置的系統(tǒng)性變化。結(jié)果表明，假想溫度高的快速淬火玻璃的光譜表現(xiàn)出向較短波長(zhǎng)的偏移，從而使它們看起來更富二氧化硅。

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  • 作者

    Bradley, James Thomson.;

  • 作者單位

    Brown University.;

  • 授予單位 Brown University.;
  • 學(xué)科 Geology.; Physics Astronomy and Astrophysics.
  • 學(xué)位 Ph.D.
  • 年度 2006
  • 頁碼 180 p.
  • 總頁數(shù) 180
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類 地質(zhì)學(xué);天文學(xué);
  • 關(guān)鍵詞

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