McCollom Thomas M, Hynek Brian M
Center for Astrobiology, University of Colorado, Boulder, Colorado 80309, USA.
Nature. 2005 Dec 22;438(7071):1129-31. doi: 10.1038/nature04390.
Exposed bedrocks at Meridiani Planum on Mars display chemical and mineralogical evidence suggesting interaction with liquid water. On the basis of morphological observations as well as high abundances of haematite and sulphate minerals, the rocks have been interpreted as sediments that were deposited in a shallow body of briny water with subsequent evaporation leaving behind the sulphate minerals. The iron-sulphur mineralization at Meridiani has also been inferred to be analogous to that produced during oxidative weathering of metal sulphide minerals, such as occurs at acid mine drainage sites. Neither of these interpretations, however, is consistent with the chemical composition of the rocks. Here we propose an alternative model for diagenesis of Meridiani bedrock that involves deposition of volcanic ash followed by reaction with condensed sulphur dioxide- and water-bearing vapours emitted from fumaroles. This scenario does not require prolonged interaction with a standing body of surface water and may have occurred at high temperatures. Consequently, the model invokes an environment considerably less favourable for biological activity on Mars than previously proposed interpretations.
火星子午线平原暴露的基岩显示出化学和矿物学证据，表明其与液态水发生过相互作用。基于形态学观察以及赤铁矿和硫酸盐矿物的高丰度，这些岩石被解释为沉积在浅盐水体中的沉积物，随后蒸发留下了硫酸盐矿物。子午线地区的铁 - 硫矿化作用也被推断与金属硫化物矿物氧化风化过程中产生的矿化作用类似，比如在酸性矿山排水点发生的情况。然而，这些解释都与岩石的化学成分不一致。在此，我们提出了一种关于子午线基岩成岩作用的替代模型，该模型涉及火山灰的沉积，随后与从喷气孔排放出的含二氧化硫和水的冷凝蒸汽发生反应。这种情况不需要与地表水长期相互作用，并且可能发生在高温下。因此，该模型所涉及的环境对火星上生物活动的适宜程度远低于先前提出的解释。
