Souza-Egipsy Virginia, Ormö Jens, Beitler Bowen Brenda, Chan Marjorie A, Komatsu Goro
Centro de Astrobiología, Instituto Nacional de Técnica Aeroespacial, Torrejón de Ardoz, Madrid, Spain.
Astrobiology. 2006 Aug;6(4):527-45. doi: 10.1089/ast.2006.6.527.
Two terrestrial environments that have been proposed as analogs for the iron oxide precipitation in the Meridiani Planum region of Mars include the Rio Tinto precipitates and southern Utah marble concretions. Samples of two typical Utah iron oxide concretions and iron oxide precipitates in contact with biofilms from Rio Tinto have been studied to determine whether evidence could be found for biomediation in the precipitation process and to identify likely locations for fossil microorganisms. Scanning electron microscopy, energy dispersive X-ray, and gas chromatography-mass spectrometry (GC-MS) were used to search for biosignatures in the Utah marbles. The precipitation of iron oxides resembles known biosignatures, though organic compounds could not be confirmed with GC-MS analysis. In contrast, textural variations induced by biological activity are abundant in the modern Rio Tinto samples. Although no compelling evidence of direct or indirect biomediation was found in the Utah marbles, the ultrastructure of the iron oxide cement in the concretion suggests an inward growth during concretion precipitation from an initially spherical redox front. No indication for growth from a physical nucleus was found.
已被提议作为火星子午线平原地区氧化铁沉淀类似物的两种陆地环境包括力拓河沉淀物和犹他州南部的大理石结核。对来自犹他州的两种典型氧化铁结核样本以及与力拓河生物膜接触的氧化铁沉淀物进行了研究，以确定是否能找到沉淀过程中生物介导作用的证据，并确定可能存在化石微生物的位置。利用扫描电子显微镜、能量色散X射线和气相色谱 - 质谱联用仪（GC - MS）在犹他州大理石中寻找生物特征。氧化铁的沉淀类似于已知的生物特征，尽管通过GC - MS分析无法确认有机化合物的存在。相比之下，在现代力拓河样本中，由生物活动引起的纹理变化很丰富。虽然在犹他州大理石中未发现直接或间接生物介导作用的确凿证据，但结核中氧化铁胶结物的超微结构表明，在结核沉淀过程中，从最初的球形氧化还原前沿向内生长。未发现从物理核生长的迹象。
