美国芝加哥大学Edwin S. Kite团队研究了火星上碳酸盐的形成和可居住性的波动。2025年7月2日出版的《自然》杂志发表了这项成果。

火星表面宜居性丧失的原因尚不清楚，同位素数据表明存在碳酸盐的“缺失汇”。火星沉积岩记录了过去地表和浅层地下液态水的气候，包括盖尔陨石坑约4公里厚的地层。这些水域是间歇性的，在空间上是不连续的，并且在火星历史的后期持续存在——如果沉积岩层像在地球上一样将二氧化碳封存为丰富的碳酸盐（最近在盖尔现场得到证实），这些属性是可以理解的。 

研究组表明，太阳光度、液态水和碳酸盐形成之间的负反馈可以解释间歇性火星绿洲的存在。在该模型中，增加太阳光度促进了液态水的稳定性，进而形成碳酸盐，降低了大气二氧化碳的分压，限制了液态水。混沌轨道强迫调制干湿循环。负反馈将液态水限制在绿洲和火星上，使其作为沙漠星球自我调节。研究组将融雪建模为水源，但反馈也可以将地下水作为水源。模型输出表明，盖尔忠实地记录了地表和近地表环境中液态水稳定性的预期主要事件。最终，大气厚度接近水的三相点，削弱了液态水的持续稳定性，从而降低了地表环境中的宜居性。研究组假设在盖尔发现的碳酸盐含量具有代表性，因此他们提出了一个可测试的想法，而非确凿的证据。

附：英文原文

Title: Carbonate formation and fluctuating habitability on Mars

Author: Kite, Edwin S., Tutolo, Benjamin M., Turner, Madison L., Franz, Heather B., Burtt, David G., Bristow, Thomas F., Fischer, Woodward W., Milliken, Ralph E., Fraeman, Abigail A., Zhou, Daniel Y.

Issue&Volume: 2025-07-02

Abstract: The cause of Mars’s loss of surface habitability is unclear, with isotopic data suggesting a ‘missing sink’ of carbonate1. Past climates with surface and shallow-subsurface liquid water are recorded by Mars’s sedimentary rocks, including strata in the approximately 4-km-thick record at Gale Crater2. Those waters were intermittent, spatially patchy and discontinuous, and continued remarkably late in Mars’s history3—attributes that can be understood if, as on Earth, sedimentary-rock formation sequestered carbon dioxide as abundant carbonate (recently confirmed in situ at Gale4). Here we show that a negative feedback among solar luminosity, liquid water and carbonate formation can explain the existence of intermittent Martian oases. In our model, increasing solar luminosity promoted the stability of liquid water, which in turn formed carbonate, reduced the partial pressure of atmospheric carbon dioxide and limited liquid water5. Chaotic orbital forcing modulated wet–dry cycles. The negative feedback restricted liquid water to oases and Mars self-regulated as a desert planet. We model snowmelt as the water source, but the feedback can also work with groundwater as the water source. Model output suggests that Gale faithfully records the expected primary episodes of liquid water stability in the surface and near-surface environment. Eventually, atmospheric thickness approaches water’s triple point, curtailing the sustained stability of liquid water and thus habitability in the surface environment. We assume that the carbonate content found at Gale is representative, and as a result we present a testable idea rather than definitive evidence.

DOI: 10.1038/s41586-025-09161-1

Source: https://www.nature.com/articles/s41586-025-09161-1