Comets and the Origin of Life

According to the Oparin-Haldane Hypothesis, the origin of life could be explained through chemical and physical processes. Thus, biological evolution was preceded by a period of chemical evolution during which formation and organization of bio-organic compounds accomplished (Oró et al., 1990; Negrón-Mendoza and Albarrán, 1993). Many scenarios have been proposed to explain the origin of life on Earth, and the role that comets may have played has been extensively recognized (Oró, 1961; Oró 2000). Comets and asteroids can be considered to have been beneficial for prebiotic synthesis in mainly two ways: as carriers, bringing organics and other components and as fuels, providing the energy necessary for the synthesis of more complex molecules (Whittet, 1997; Lyons and Vasavada, 1999; Pierazzo and Chyba, 1999).

Earth was formed in a particular region of the solar nebulae; because of this, it was depleted of molecular material. Consequently, the molecules and organic materials that comets brought to the primitive atmosphere may have been important for the emergence of life on Earth (Chyba and Sagan, 1992; Owen and Bar-Nun, 2001).

The organic contribution of comets to the early Earth may have been crucial because cometary impacts could have delivered organics to the surface of the early Earth. The contribution of those bodies is noteworthy in the case of some molecules, especially CN- bearing molecules, such as HCN, that are abundant through the universe and were probably scarce on Earth due to its high volatility.

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