Delivery of organics to Mars through asteroid and comet impacts
Delivery of organics to Mars through asteroid and comet impacts
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DOI：
10.1016/j.icarus.2018.03.006
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发表时间：
2018-07-15
期刊：
影响因子：
3.2
通讯作者：
Greenstreet, Sarah
中科院分区：
文献类型：
--
作者：
Frantseva, Kateryna;Mueller, Michael;Greenstreet, Sarah
鉴于快速的光分解和光降解，最近在火星地下和大气中发现的有机物可能是在地质学上最近的时期提供的。可能的母体是C型小行星、彗星和行星际尘埃颗粒（IDP）。使用不同的方法估计，尘埃沉降率在0.71和2.96 x 10（6）kg/年之间（Nesvorny等人，2011; Bohn等人，2017; Crismani等人，假设碳含量为10%（Flynn，1996），这意味着IDP碳通量为0.07 - 0.3 x 10（6）kg/年。我们首次计算了小行星和彗星撞击产生的碳通量，并对火星撞击速率进行了动力学模拟。我们使用N-体积分RMVS/Swif ter传播太阳和八大行星从他们的当前位置。我们分别将彗星和小行星作为无质量测试粒子添加到模拟中，基于它们当前的轨道要素，得出火星撞击率为4.34 x 10（-3）彗星/百万年和3.3小行星/百万年。在小行星中，只有C型含有可观数量的碳。由于缺乏关于火星撞击物的直接分类信息，我们根据测量的分类类型分布，结合穿越火星的小行星起源的动力学模型，估计彗星撞击火星的全球碳通量在一个数量级内近似为0.013 x 10（6）kg/yr，而小行星的释放量约为0.05 x 10（6）千克/年。这些值分别相当于Nesvorny等人估计的国内流离失所者碳通量的4 - 19%和17 - 71%，与空间上均匀的IDP下落不同，撞击喷出物是局部分布的，集中在撞击地点周围。我们发现小行星和彗星的有机物在距离陨石坑中心150公里的地方占主导地位。我们的研究结果可能是重要的解释在火星上的有机物原位检测。(C)2018爱思唯尔公司All rights reserved.
Given rapid photodissociation and photodegradation, the recently discovered organics in the Martian subsurface and atmosphere were probably delivered in geologically recent times. Possible parent bodies are C-type asteroids, comets, and interplanetary dust particles (IDPs).The dust infall rate was estimated, using different methods, to be between 0.71 and 2.96 x 10(6) kg/yr (Nesvorny et al., 2011; Bohn et al., 2017; Crismani et al., 2017); assuming a carbon content of 10% (Flynn, 1996), this implies an IDP carbon flux of 0.07 - 0.3 x 10(6) kg/yr. We calculate for the first time the carbon flux from impacts of asteroids and comets.To this end, we perform dynamical simulations of impact rates on Mars. We use the N-body integrator RMVS/Swif ter to propagate the Sun and the eight planets from their current positions. We separately add comets and asteroids to the simulations as massless test particles, based on their current orbital elements, yielding Mars impact rates of 4.34 x 10(-3) comets/Myr and 3.3 asteroids/Myr.We estimate the delivered amount of carbon using published carbon content values. In asteroids, only C types contain appreciable amounts of carbon. Given the absence of direct taxonomic information on the Mars impactors, we base ourselves on the measured distribution of taxonomic types in combination with dynamic models of the origin of Mars-crossing asteroids.We estimate the global carbon flux on Mars from cometary impacts to be similar to 0.013 x 10(6) kg/yr within an order of magnitude, while asteroids deliver similar to 0.05 x 10(6) kg/yr. These values correspond to similar to 4 - 19% and similar to 17 - 71%, respectively, of the IDP-borne carbon flux estimated by Nesvorny et al., Bohn et al. and Crismani et al. Unlike the spatially homogeneous IDP infall, impact ejecta are distributed locally, concentrated around the impact site. We find organics from asteroids and comets to dominate over IDP-borne organics at distances up to 150 km from the crater center. Our results may be important for the interpretation of in situ detections of organics on Mars. (C) 2018 Elsevier Inc. All rights reserved.