Composition of terrestrial planets records planetary accretion, core–mantle and crust–mantle differentiation, and surface processes. Here we compare the compositional models of Earth and Mars to reveal their characteristics and formation processes. Earth and Mars are equally enriched in refractory elements (1.9 × CI), although Earth is more volatile-depleted and less oxidized than Mars. Their chemical compositions were established by nebular fractionation, with negligible contributions from post-accretionary losses of moderately volatile elements. The degree of planetary volatile element depletion might correlate with the abundances of chondrules in the accreted materials, planetary size, and their accretion timescale, which provides insights into composition and origin of Mercury, Venus, the Moon-forming giant impactor, and the proto-Earth. During its formation before and after the nebular disk's lifetime, the Earth likely accreted more chondrules and less matrix-like materials than Mars and chondritic asteroids, establishing its marked volatile depletion. A giant impact of an oxidized, differentiated Mars-like (i.e., composition and mass) body into a volatile-depleted, reduced proto-Earth produced a Moon-forming debris ring with mostly a proto-Earth's mantle composition. Chalcophile and some siderophile elements in the silicate Earth added by the Mars-like impactor were extracted into the core by a sulfide melt (∼0.5% of the mass of the Earth's mantle). In contrast, the composition of Mars indicates its rapid accretion of lesser amounts of chondrules under nearly uniform oxidizing conditions. Mars’ rapid cooling and early loss of its dynamo likely led to the absence of plate tectonics and surface water, and the present-day low surface heat flux. These similarities and differences between the Earth and Mars made the former habitable and the other inhospitable to uninhabitable.

类地行星的组成记录了行星的吸积、核-幔和壳-幔分异和地表过程。在这里，我们比较了地球和火星的成分模型，以揭示它们的特征和形成过程。地球和火星同样富含难熔元素 (1.9 × CI)，尽管地球比火星更缺乏挥发性和更少氧化。它们的化学成分是通过星云分馏确定的，中等挥发性元素的增生后损失可以忽略不计。行星挥发性元素消耗的程度可能与吸积物质中球粒的丰度、行星大小及其吸积时间尺度有关，这提供了对水星、金星、月球形成巨行星撞击器和原始行星的组成和起源的深入了解。地球。在星云盘存在之前和之后的形成过程中，与火星和球粒状小行星相比，地球可能吸积了更多的球粒和更少的基质类物质，从而确立了其显着的挥发性消耗。一个氧化的、分化的火星状（即成分和质量）天体与挥发物耗尽、还原的原地球的巨大撞击产生了一个形成月球的碎片环，其中大部分是原地球的地幔成分。由类火星撞击器添加的地球硅酸盐中的亲硫元素和一些亲铁元素被硫化物熔体（地球地幔质量的 0.5%）提取到地核中。相比之下，火星的组成表明它在几乎均匀的氧化条件下迅速增加了较少量的球粒。火星的快速冷却和发电机的早期丧失可能导致板块构造和地表水的缺失，以及当今低地表热通量。地球和火星之间的这些异同使得前者宜居，而后者不适宜居住。