While NASA imagery has shown evidence of ancient rivers and lakes on Mars that transitioned to dry dunes, uncertainty remains over the timing of the environmental changes that may have contributed to these shifts.
尽管美国宇航局的图像显示了火星上古老河流和湖泊转变为干燥沙丘的证据，但可能导致这些转变的环境变化的时间仍然存在不确定性。
Now, data collected by NASA’s Curiosity rover has revealed that individual crystals in the iron oxide hematite can be used as a mineralogical marker of changes to Mars’ ancient climate. Because the shape and structure of these crystallites reflect the conditions – such as temperature and water presence – under which they were formed, they can serve as an indicator of when these changes occurred.
现在，美国宇航局好奇号探测器收集的数据表明，氧化铁赤铁矿中的单个晶体可以用作火星古代气候变化的矿物学标记。由于这些微晶的形状和结构反映了它们形成的条件（例如温度和水的存在），因此它们可以作为这些变化何时发生的指标。
Scientists studied 20 samples collected by Curiosity across various elevations throughout Gale Crater for a paper published Thursday in Science . Gale Crater’s walls reveal Mars’ environmental history layer by layer, with deeper elevations capturing its earliest years. The team analyzed data from the rover’s Chemistry and Minerology (CheMin) instrument and discovered that hematite showed different crystallite sizes at different elevations. They also discovered that goethite, a mineral that typically forms alongside hematite, was absent in samples from lower elevations but still present in samples from higher elevations. This suggests that warm groundwater might have remained for up to 4.7 million years in the deepest layers of Gale Crater and that during much of this time, these long-lived aquifers could have been potentially habitable.
周四，科学家们在《科学》杂志上发表了一篇论文，研究了好奇号在盖尔陨石坑不同海拔地区收集的 20 个样本。盖尔陨石坑的墙壁逐层揭示了火星的环境历史，更深的海拔记录了它的最早岁月。研究小组分析了火星车化学和矿物学（CheMin）仪器的数据，发现赤铁矿在不同海拔处显示出不同的晶粒尺寸。他们还发现，针铁矿（一种通常与赤铁矿一起形成的矿物）在较低海拔的样品中不存在，但在较高海拔的样品中仍然存在。这表明，温暖的地下水可能在盖尔陨石坑最深处保留了长达 470 万年，并且在这段时间内的大部分时间里，这些长寿的含水层可能适合居住。
“What we found was that warm and wet conditions were present for extended periods in buried rocks, despite Mars’ climate becoming colder,” said Tanya Peretyazhko, co-first author of the study and planetary scientist in the Astromaterials Research and Exploration Science division at NASA’s Johnson Space Center in Houston. “It means that deep in those rocks, those warmer conditions could have made for habitable conditions for much longer periods of time, provided that other essential factors were present.”
该研究的共同第一作者、休斯敦美国宇航局约翰逊航天中心天体材料研究和探索科学部门的行星科学家坦尼娅·佩雷亚日科（Tanya Peretyazhko）说：“我们发现，尽管火星的气候变得更冷，但埋藏的岩石中长期存在温暖和潮湿的条件。” “这意味着，如果存在其他重要因素，那么在这些岩石深处，那些温暖的条件可能会在更长的时间内创造出适宜居住的条件。”
Iron oxides are considered indicators of water activity because they form in its presence. This study shows that hematite can also be a marker of climate changes based on its crystallite sizes and structures, which change under different temperatures. The scientists found that hematite crystallites from higher elevations in Gale Crater were less than 10 nanometers in size, while crystallites from lower locations were generally larger, reaching up to 65 nanometers. These findings aligned with the observations that samples from higher elevations contained both hematite and goethite, while lower elevation samples lacked goethite.
氧化铁被认为是水活度的指标，因为它们是在氧化铁存在的情况下形成的。这项研究表明，根据其微晶尺寸和结构在不同温度下的变化，赤铁矿也可以成为气候变化的标志。科学家发现，盖尔陨石坑较高海拔地区的赤铁矿微晶尺寸小于10纳米，而较低位置的赤铁矿微晶尺寸普遍较大，可达65纳米。这些发现与观察结果一致，即来自较高海拔的样品含有赤铁矿和针铁矿，而较低海拔的样品不含针铁矿。
They concluded that, under warmer conditions when the pH of water is neutral or slightly alkaline, goethite can transform into hematite. These warmer conditions also favored an increase in hematite crystallite size in the deeper layers of Gale Crater through a process known as Ostwald ripening, in which smaller crystallites dissolve and contribute to the growth of larger ones.
他们得出的结论是，在较温暖的条件下，当水的 pH 值为中性或弱碱性时，针铁矿可以转化为赤铁矿。这些温暖的条件也有利于盖尔陨石坑深层赤铁矿微晶尺寸的增加，这一过程被称为奥斯特瓦尔德熟化，在此过程中较小的微晶溶解并有助于较大微晶的生长。
“This can tell you that the top layers were colder and didn’t have enough water, or the water presence was relatively short-lived, so the crystallites didn’t have sufficient time and conditions to grow in size,” said Peretyazhko. “But the lower layers had longstanding warm water that allowed those crystallites to grow.”
“这可以告诉你，表层温度较低，没有足够的水，或者水的存在时间相对较短，因此微晶没有足够的时间和条件来长大，”佩列特亚日科说。 “但下层长期存在温水，可以让这些晶体生长。”
A unique highlight of this study is that the data comes from Martian samples, rather than from theoretical modeling. Curiosity’s robotic arm delivered powdered rock to CheMin’s input funnel, where it was analyzed. “With CheMin’s X-ray diffraction patterns, we can look at the hematite crystal’s size and dimensions, information that that can’t be gathered from satellite analysis of the Martian surface.” said Tom Bristow, principal investigator of the CheMin instrument at NASA’s Ames Research Center in California’s Silicon Valley.
这项研究的一个独特亮点是数据来自火星样本，而不是来自理论模型。好奇号的机械臂将石粉输送到 CheMin 的输入漏斗中，并在那里进行分析。 “利用 CheMin 的 X 射线衍射图，我们可以查看赤铁矿晶体的大小和尺寸，这是无法通过火星表面卫星分析收集到的信息。”加州硅谷 NASA 艾姆斯研究中心 CheMin 仪器首席研究员 Tom Bristow 说道。
Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California, said CheMin is capable of making measurements with extraordinary scientific fidelity.
美国宇航局南加州喷气推进实验室的好奇号项目科学家阿什温·瓦萨瓦达 (Ashwin Vasavada) 表示，CheMin 能够以非凡的科学保真度进行测量。
“It doesn’t just tell you there is hematite,” Vasavada explained. “One can use the data to extract the size and shape of the hematite crystallites and the presence of other related minerals, all of which were necessary to produce this result.”
“它不仅仅告诉你有赤铁矿，”瓦萨瓦达解释道。 “人们可以利用这些数据来提取赤铁矿微晶的大小和形状以及其他相关矿物的存在，所有这些都是产生这一结果所必需的。”
Curiosity was built by NASA JPL, which is managed by Caltech in Pasadena, California. NASA JPL leads the mission on behalf of NASA’s Science Mission Directorate in Washington as part of NASA’s Mars Exploration Program portfolio. CheMin, led by NASA Ames , is one of 10 science instruments aboard Curiosity and has a cross-country team of scientists, including researchers at NASA Ames, University of Arizona, California Institute of Technology, Planetary Science Institute, Carnegie Institution for Science, Lunar and Planetary Institute, JPL, NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and NASA’s Johnson. The team combines expertise in mineralogy, petrology, materials science, astrobiology and soil science, with experience studying terrestrial, lunar and Martian rocks.
好奇号由美国宇航局喷气推进实验室建造，由加利福尼亚州帕萨迪纳市的加州理工学院管理。作为 NASA 火星探索计划组合的一部分，NASA 喷气推进实验室代表位于华盛顿的 NASA 科学任务理事会领导这项任务。由 NASA 艾姆斯领导的 CheMin 是好奇号上的 10 个科学仪器之一，拥有一支跨国科学家团队，包括来自 NASA 艾姆斯、亚利桑那大学、加州理工学院、行星科学研究所、卡内基科学研究所、月球与行星研究所、喷气推进实验室、位于马里兰州格林贝尔特的 NASA 戈达德太空飞行中心和 NASA 约翰逊的研究人员。该团队结合了矿物学、岩石学、材料科学、天体生物学和土壤科学方面的专业知识，以及研究陆地、月球和火星岩石的经验。
For more information on NASA’s Curiosity rover, visit:
有关 NASA 好奇号漫游车的更多信息，请访问：
Karen Fox / Alana Johnson Headquarters, Washington 240-285-5155 / 202-672-4780 karen.c.fox@nasa.gov / alana.r.johnson@nasa.gov
凯伦·福克斯 / 阿兰娜·约翰逊 华盛顿总部 240-285-5155 / 202-672-4780 karen.c.fox@nasa.gov / alana.r.johnson@nasa.gov
Victoria Segovia Johnson Space Center, Houston 281-483-5111 victoria.segovia@nasa.gov
维多利亚·塞戈维亚·约翰逊航天中心，休斯顿 281-483-5111 victoria.segovia@nasa.gov