碳质球粒陨石有机物红外光谱研究

Study on MIR Spectra of Organic Matter in Carbonaceous Chondrite

碳质球粒陨石是太阳系中最原始的物质之一.通过对碳质球粒陨石的光谱分析,可以建立其与母体小行星之间的联系,有助于探测小行星表面物质成分、研究太阳系早期的演化历史.研究了6个CM2型碳质球粒陨石和11个煤炭样品(碳质球粒陨石所含有机质的地球类比物)可见-远红外谱段反射光谱特征,并分析了它们与有机组分的关系.结果表明,对于不同类型的煤样随着煤化程度的升高,各有机物碳氢基团的吸收峰深度逐渐降低, 3.41μm处脂肪族碳氢化合物的吸收深度与H/C比存在线性正相关,当H/C比小于0.55时, 3.41μm处无明显光谱吸收特征.在3–4μm区域, CM2陨石存在明显的脂肪族CH2、CH3吸收带,缺乏3.28μm芳香族CH吸收带,但在5–6.5μm区域存在微弱的芳香族C=C、CO吸收带,指示CM2碳质球粒陨石的有机组分含有脂肪族和芳香族.陨石红外光谱中3.28μm和5–6.5μm区域光谱特征不明显可能是因为在此波段区域存在含水矿物OH的重叠吸收或受到其他不透明矿物的影响,具体原因有待进一步研究.研究也说明,需要更长的波段范围才能够准确识别小天体有机质类型.

Carbonaceous chondrites are one of the most primitive substances in the solar system.Through the spectral analysis of carbonaceous chondrites,the relationship between them and the parent asteroid can be established,which is helpful to analyze the composition of the surface of the asteroid and the early evolutionary history of the solar system.In this paper,the relationship between the visible-far infrared reflectance spectra of 6 CM2 carbonaceous chondritesand and 11 coal samples(earth analogs of organic matter contained in carbonaceous chondrites)and their organic components was studied.The results of the study show that for different types of coal samples,as the degree of coalification increases,the depth of the absorption peak of each organic hydrocarbon group continues to decrease.The depth of aliphatic hydrocarbons at 3.41μm was linearly positive correlated with the H/C ratio,when the H/C ratio was less than 0.55,there was no obvious spectral characteristic at 3.41μm.In the 3-4μm region,the CM2 meteorites have obvious aliphatic CH2 and CH3 absorption,lacking 3.28μm aromatic CH absorption,but in the 5-6.5μm region,there are weak aromatic C=C and CO absorption.This indicates that the organic components of CM2 carbonaceous chondrites contain aliphatic and aromatic groups.The spectral features of the 3.28μm and 5-6.5μm regions of the meteorite are not obvious,which may be due to the overlapping absorption of water-bearing mineral OH in this band or the influence of other opaque minerals,the specific reasons for which need to be further studied.This study also indicates that a longer band range is needed to reliably identify the organic matter types of asteroids.