As Origens: Uma história de 13,7 bilhões de anos.

Abstract

The origins of the universe and the formation of planet Earth are central themes in the biological sciences, especially in paleontology, as they help us understand the evolution of life. Nucleosynthesis, the process of forming chemical elements in astrophysical environments, predominantly occurs within stars. In the 1940s and 1950s, the primary hypotheses regarding the origin of elements in the solar system emerged. The first, Big Bang nucleosynthesis, explains the formation of light elements, such as hydrogen and helium, shortly after the creation of the universe. However, it does not account for the formation of heavier elements, such as carbon and oxygen, which are essential for life. The second hypothesis, stellar nucleosynthesis, describes how stars produce heavier elements through nuclear reactions and, upon exploding as supernovae, disperse enriched materials into space, contributing to the formation of new stars and planets. Earth's formation took place in regions known as nebulae, where gravity overcomes gas pressure, leading to the birth of new stars and protoplanetary disks. Rocky material near the star coalesces to form terrestrial planets, while gases and ice at greater distances accumulate to create gas giants. Martian meteorites indicate that Mars may have once harbored liquid water, leading to the hypothesis that life could have originated on Mars. This raises the possibility of panspermia, the idea that life on Earth and Mars may share a common origin. The Giant Impact Hypothesis, which explains the Moon’s formation, suggests that an object the size of Mars collided with early Earth, ejecting debris that eventually formed the Moon. Following this impact, Earth cooled, enabling the formation of oceans, which are essential for life. For life to exist, liquid water, organic matter, and suitable conditions for nucleotide formation are necessary. Stanley Miller's 1953 experiment demonstrated that basic organic molecules can be synthesized under conditions mimicking those of early Earth, supporting the theory of abiogenesis. The panspermia hypothesis suggests that life may have been delivered to Earth by meteorites. The transition from organic matter to self-sustaining life forms remains one of science's greatest mysteries. Nucleosynthesis, stellar formation, and the conditions required for life are interconnected, shaping both Earth and the universe, and their study illuminates the origins of our existence.