Samulewski Rafael Block, Gonçalves Josué Martins, Urbano Alexandre, da Costa Antônio Carlos Saraiva, Ivashita Flávio F, Paesano Andrea, Zaia Dimas Augusto Morozin
Departamento de Química, Universidade Estadual de Londrina, CEP 86057-970 Londrina, PR, Brazil.
Departamento de Química Fundamental, Universidade de São Paulo-USP, CEP 05508-000 São Paulo, SP, Brazil.
Life (Basel). 2020 Apr 2;10(4):34. doi: 10.3390/life10040034.
Magnetite is an iron oxide mineral component of primitive Earth. It is naturally synthesized in different ways, such as magma cooling as well as olivine decomposition under hydrothermal conditions. It is probable magnetite played a significant role in biogenesis. The seawater used in the current work contained high Mg, Ca and SO concentrations, unlike the seawater of today that has high Na and Cl concentrations. It is likely that this seawater better resembled the ion composition of the seas of the Earth from 4 billion years ago. Cyanide and thiocyanate were common molecules in prebiotic Earth, and especially in primitive oceans, where they could act on the magnetite mechanism synthesis via Fe interaction. In this research, magnetite samples that were synthesized under prebiotic conditions in the presence of cyanide or thiocyanate, (both with and without artificial seawater), showed that, besides magnetite, goethite and ferrihydrite can be produced through different Fe-ion interactions. Cyanide apparently acts as a protective agent for magnetite production; however, thiocyanate and seawater 4.0 Gy ions produced goethite and ferrihydrite at different ratios. These results validate that Fe oxides/hydroxides were possibly present in primitive Earth, even under anoxic conditions or in the absence of UV radiation. In addition, the results show that the composition of water in early oceans should not be neglected in prebiotic chemistry experiments, since this composition directly influences mineral formation.
磁铁矿是原始地球的一种氧化铁矿物成分。它通过不同方式自然合成，比如岩浆冷却以及水热条件下橄榄石的分解。磁铁矿很可能在生物起源过程中发挥了重要作用。当前研究中使用的海水含有高浓度的镁、钙和硫酸根离子，与如今高钠和氯离子浓度的海水不同。这种海水可能更类似于40亿年前地球海洋的离子组成。氰化物和硫氰酸盐是前生物地球，尤其是原始海洋中的常见分子，它们可以通过铁相互作用作用于磁铁矿的合成机制。在这项研究中，在有氰化物或硫氰酸盐（有或没有人工海水）存在的前生物条件下合成的磁铁矿样品表明，除了磁铁矿之外，针铁矿和水铁矿也可以通过不同的铁离子相互作用产生。氰化物显然作为磁铁矿生成的保护剂；然而，硫氰酸盐和海水4.0戈瑞离子以不同比例生成针铁矿和水铁矿。这些结果证实，即使在缺氧条件下或没有紫外线辐射的情况下，铁的氧化物/氢氧化物也可能存在于原始地球。此外，结果表明，在生命起源前的化学实验中，早期海洋水的成分不应被忽视，因为这种成分直接影响矿物的形成。
