Kinohi Institute, Pasadena, California 91101, USA.
Astrobiology. 2009 Dec;9(10):953-64. doi: 10.1089/ast.2009.0353.
The European Space Agency will launch the ExoMars mission in 2016 with a primary goal of surveying the martian subsurface for evidence of organic material. We have recently investigated the utility of including either a 365 nm light-emitting diode or a 375 nm laser light source in the ExoMars rover panoramic camera (PanCam). Such a modification would make it feasible to monitor rover drill cuttings optically for the fluorescence signatures of aromatic organic molecules and map the distribution of polycyclic aromatic hydrocarbons (PAHs) as a function of depth to the 2 m limit of the ExoMars drill. The technique described requires no sample preparation, does not consume irreplaceable resources, and would allow mission control to prioritize deployment of organic detection experiments that require sample destruction, expenditure of non-replaceable consumables, or both. We report here for the first time laser-induced fluorescence emission (L.I.F.E.) imaging detection limits for anthracene, pyrene, and perylene targets doped onto a Mars analog granular peridotite with a 375 nm Nichia laser diode in optically uncorrected wide-angle mode. Data were collected via the Beagle 2 PanCam backup filter wheel fitted with original blue (440 nm), green (530 nm), and red (670 nm) filters. All three PAH species can be detected with the PanCam green (530 nm) filter. Detection limits in the green band for signal-to-noise ratios (S/N) > 10 are 49 parts per million (ppm) for anthracene, 145 ppm for pyrene, and 20 ppm for perylene. The anthracene detection limit improves to 7 ppm with use of the PanCam blue filter. We discuss soil-dependent detection limit constraints; use of UV excitation with other rover cameras, which provides higher spatial resolution; and the advantages of focused and wide-angle laser modes. Finally, we discuss application of L.I.F.E. techniques at multiple wavelengths for exploration of Mars analog extreme environments on Earth, including Icelandic hydrothermally altered basalts and the ice-covered lakes and glaciers of Dronning Maud Land, Antarctica.
欧洲空间局将于 2016 年发射 ExoMars 任务，主要目标是勘测火星地下是否存在有机物质的证据。我们最近研究了在 ExoMars 漫游车全景相机 (PanCam) 中加入 365nm 发光二极管或 375nm 激光光源的效用。这种修改将使监测漫游车钻取的岩屑的芳香族有机分子荧光特征以及根据深度绘制多环芳烃 (PAH) 的分布成为可能，深度达到 ExoMars 钻头的 2m 极限。该技术不需要样品制备，不消耗不可替代的资源，并允许任务控制优先部署需要样品破坏、消耗不可替代消耗品或两者兼有的有机检测实验。我们在这里首次报告了在未经过光学校正的广角模式下，使用 375nm 的 Nichia 激光二极管对掺杂在火星模拟粒状橄榄岩上的蒽、芘和并五苯目标进行激光诱导荧光发射 (L.I.F.E.) 成像检测限。数据通过 Beagle 2 PanCam 备份滤光轮收集，该滤光轮配备了原始的蓝色 (440nm)、绿色 (530nm) 和红色 (670nm) 滤光片。使用 PanCam 绿色 (530nm) 滤光片可以检测到所有三种 PAH 物质。信噪比 (S/N) > 10 的绿色波段的检测限分别为蒽 49ppm、芘 145ppm 和并五苯 20ppm。使用 PanCam 蓝色滤光片，蒽的检测限提高到 7ppm。我们讨论了土壤相关的检测限限制；使用其他漫游车相机进行紫外激发，这提供了更高的空间分辨率；以及聚焦和广角激光模式的优势。最后，我们讨论了在多个波长下应用 L.I.F.E. 技术探索地球模拟火星极端环境，包括冰岛水热蚀变玄武岩以及南极的丹宁莫德地德朗宁湖和冰川。
