The contribution of sulphur dioxide from ablating micrometeorites to the atmospheres of Earth and Mars
The contribution of sulphur dioxide from ablating micrometeorites to the atmospheres of Earth and Mars
复制标题
DOI：
10.1016/j.gca.2011.01.029
复制
发表时间：
2011-04
影响因子：
5
通讯作者：
R. Court;M. Sephton
中科院分区：
文献类型：
--
作者：
R. Court;M. Sephton
大气成分是控制气候和行星表面可居住性的关键因素。微陨石的消融被认为是改变大气化学的一种方式，特别是在太阳系历史上外来物质的坠落率很高的时候。尽管它有可能影响气候和可居住性，但目前地外二氧化硫对类地行星大气的贡献还无法量化。我们已经使用快速热解来模拟大气中的微陨石和傅里叶变换红外光谱法，以确定和量化的二氧化硫产生的碳质陨石Orgueil（CI 1），ALH 88045（CM 1），冷Bokkeveld（CM 2），默奇森（CM 2）和Mokoia（CV 3）。我们已经用这种方法来了解二氧化硫从坠落的微陨石引入地球和火星的大气层。硫酸盐，以几个重量%存在于碳质碳酸盐中，抗热分解，限制未熔化的微陨石产生二氧化硫。微陨石是现今地球和火星上二氧化硫的次要来源，估计分别高达约2400吨和350吨。在后期重撞击（LHB）期间，微陨石尘埃的沉降速率更大，计算出早期地球的二氧化硫平均产生速率约为20Mtyr− 1，早期火星的二氧化硫平均产生速率约为0.5Mtyr− 1，而LHB为1亿年。在高海拔地区，二氧化硫的这种输送率会通过平流层硫酸盐气溶胶散射阳光，减少到达这些行星表面的太阳能，并可能通过促进较冷的气候和减少行星表面液态水的可能性，对生物圈的发展产生不利影响。
Atmospheric composition is a key control on climate and the habitability of planetary surfaces. Ablation of infalling micrometeorites has been recognised as one way in which atmospheric chemistry can be changed, especially at times in solar system history when the infall rates of exogenous material were high. Despite its potential to influence climate and habitability, extraterrestrial sulphur dioxide is currently an unquantified contribution to the atmospheres of the terrestrial planets. We have used flash pyrolysis to simulate the atmospheric entry of micrometeorites and Fourier-transform infrared spectroscopy to identify and quantify the sulphur dioxide produced from the carbonaceous meteorites Orgueil (CI1), ALH 88045 (CM1), Cold Bokkeveld (CM2), Murchison (CM2) and Mokoia (CV3). We have used this approach to understand the introduction of sulphur dioxide to the atmospheres of Earth and Mars from infalling micrometeorites. Sulphates, present in carbonaceous chondrites at a few wt.%, are resistant to thermal decomposition, limiting the yields of sulphur dioxide from unmelted micrometeorites. Infalling micrometeorites are a minor source of present-day sulphur dioxide on Earth and Mars, calculated to be up to around 2400tonnes and about 350tonnes, respectively. During the Late Heavy Bombardment (LHB), the much greater infall rates of micrometeoritic dust are calculated to be associated with average production rates of sulphur dioxide of around 20Mtyr−1for the early Earth and 0.5Mtyr−1for early Mars, for a LHB of 100Myr. These rates of delivery of sulphur dioxide at high altitudes would have reduced the solar energy reaching the surfaces of these planets, via scattering of sunlight by stratospheric sulphate aerosols, and may have had detrimental effects on developing biospheres by promoting cooler climates and reducing the probability of liquid water on planetary surfaces.