The martian meteorite ALH 84001 formed before ∼4.0 Ga, so it could have preserved information about habitability on early Mars and habitability since then. ALH 84001 is particularly important as it contains carbonate (and other) minerals that were deposited by liquid water, raising the chance that they may have formed in a habitable environment. Despite vigorous efforts from the scientific community, there is no accepted evidence that ALH 84001 contains traces or markers of ancient martian life—all the purported signs have been shown to be incorrect or ambiguous. However, the meteorite provides evidence for three distinct episodes of potentially habitable environments on early Mars. First is evidence that the meteorite's precursors interacted with clay-rich material, formed approximately at 4.2 Ga. Second is that igneous olivine crystals in ALH 84001 were partially dissolved and removed, presumably by liquid water. Third is, of course, the deposition of the carbonate globules, which occurred at ∼15–25°C and involved near-neutral to alkaline waters. The environments of olivine dissolution and carbonate deposition are not known precisely; hydrothermal and soil environments are current possibilities. By analogies with similar alteration minerals and sequences in the nakhlite martian meteorites and volcanic rocks from Spitzbergen (Norway), a hydrothermal environment is favored. As with the nakhlite alterations, those in ALH 84001 likely formed in a hydrothermal system related to a meteoroid impact event. Following deposition of the carbonates (at 3.95 Ga), ALH 84001 preserves no evidence of habitable environments, that is, interaction with water. The meteorite contains several materials (formed by impact shock at ∼3.9 Ga) that should have reacted readily with water to form hydrous silicates, but there is no evidence any formed.

中文翻译：

---

火星上不适宜居住和可能适宜居住的环境：来自陨石 ALH 84001 的证据

火星陨石 ALH 84001 形成于 ∼4.0 Ga 之前，因此它可以保留有关早期火星宜居性和此后宜居性的信息。ALH 84001 特别重要，因为它含有由液态水沉积的碳酸盐（和其他）矿物质，增加了它们可能在宜居环境中形成的机会。尽管科学界做出了巨大努力，但没有公认的证据表明 ALH 84001 包含古代火星生命的痕迹或标记——所有声称的迹象都被证明是不正确的或模棱两可的。然而，陨石为早期火星上潜在宜居环境的三个不同事件提供了证据。首先是陨石的前体与富含粘土的物质相互作用的证据，该物质形成于大约 4.2 Ga。其次是 ALH 84001 中的火成橄榄石晶体被部分溶解和去除，可能是被液态水溶解了。当然，第三个是碳酸盐球的沉积，它发生在约 15-25°C 并且涉及近中性至碱性水。橄榄石溶解和碳酸盐沉积的环境尚不清楚；热液和土壤环境是目前的可能性。通过与来自斯匹次卑尔根（挪威）的 nakhlite 火星陨石和火山岩中的类似蚀变矿物和序列进行类比，热液环境是有利的。与 nakhlite 蚀变一样，ALH 84001 中的蚀变很可能是在与流星体撞击事件相关的热液系统中形成的。在碳酸盐沉积（3.95 Ga）之后，ALH 84001 没有保留任何可居住环境的证据，也就是说，与水的相互作用。陨石包含几种材料（由~3.9 Ga 的冲击冲击形成），它们应该很容易与水反应形成水合硅酸盐，但没有证据表明任何形成。