Squyres S W, Knoll A H, Arvidson R E, Clark B C, Grotzinger J P, Jolliff B L, McLennan S M, Tosca N, Bell J F, Calvin W M, Farrand W H, Glotch T D, Golombek M P, Herkenhoff K E, Johnson J R, Klingelhöfer G, McSween H Y, Yen A S
Department of Astronomy, Space Sciences Building, Cornell University, Ithaca, NY 14853, USA.
Science. 2006 Sep 8;313(5792):1403-7. doi: 10.1126/science.1130890.
The Mars Exploration Rover Opportunity has spent more than 2 years exploring Meridiani Planum, traveling approximately 8 kilometers and detecting features that reveal ancient environmental conditions. These include well-developed festoon (trough) cross-lamination formed in flowing liquid water, strata with smaller and more abundant hematite-rich concretions than those seen previously, possible relict "hopper crystals" that might reflect the formation of halite, thick weathering rinds on rock surfaces, resistant fracture fills, and networks of polygonal fractures likely caused by dehydration of sulfate salts. Chemical variations with depth show that the siliciclastic fraction of outcrop rock has undergone substantial chemical alteration from a precursor basaltic composition. Observations from microscopic to orbital scales indicate that ancient Meridiani once had abundant acidic groundwater, arid and oxidizing surface conditions, and occasional liquid flow on the surface.
“机遇号”火星探测车已花费两年多时间探索子午线平原，行驶了约8公里，探测到了揭示古代环境状况的特征。这些特征包括在流动液态水中形成的发育良好的波状（槽状）交错层理、与之前所见相比更小且更丰富的富含赤铁矿结核的地层、可能反映石盐形成的残留“漏斗晶体”、岩石表面厚厚的风化外皮、抗侵蚀的裂缝填充物以及可能由硫酸盐脱水导致的多边形裂缝网络。随深度的化学变化表明，露头岩石的硅质碎屑部分已从原始玄武岩成分经历了大量化学改变。从微观到轨道尺度的观测表明，古代子午线平原曾有丰富的酸性地下水、干旱且氧化的地表条件以及偶尔的地表液态水流。
