Researchers from the Higher Council for Scientific Research (CSIC) have found acommon link in the origin of the atmospheres of the Earth and Titan, the satellite of Saturn. Analysis of the data obtained by the Cassini-Huygens mission, a project of NASA, the European Space Agency (ESA) and the Italian Space Agency, suggests that the chemical evolution of both atmospheres was marked by thelast great bombardment of asteroids and comets during the formation of the Solar System, A few ago3.9 billion years.
According to CSIC scientists Josep Maria Trigo and Francisco Javier Martín, authors of the study published in the latest issue ofPlanetary & Space Science, this “great late bombardment” began when the giant planets Jupiter and Saturn migrated to their current orbits, which produced a gravitational impulse on icy bodies formed in various regions of the outer part of the Solar System. As a consequence, a large number of objects rich in water and organic matter began to impact on rocky planets like Earth.
Scientists have found great similarities between Earth and Titan, despite the fact that both planetary bodies formed very far from each other (the blue planet is nine times closer to the Sun than the satellite of Saturn). In particular, their atmospheres have in common theabundance of molecular nitrogen, deuterium, hydrogen, carbon, nitrogen, and oxygen. All these elements point to the same origin derived from the impact of comets and asteroids.
They have also carried out a thermodynamic study of the atmospheric conditions of both planetary bodies. The results suggest that the chemical evolution of both atmospheres would have been similar, marked by various impacts. ? Since the Earth was formed in a very hot environment close to the Sun, this great late bombardment was essential to enrich it with the basic ingredients for the appearance of life. In fact, most basins and large craters on the Moon were caused by the impact of these enriching objects in that period, just as the lunar rocks collected by the Apollo missions dated ?, explains Trigo, who works at the Institute of Sciences. del Espacio (CSIC) and the Institute of Space Studies of Catalonia.
According to Trigo, in addition to the lunar record of craters, there is other evidence of the important role that the impact of these objects had. One of them reveals that the composition of the earth’s crust and mantle, specifically its abundance of metals, has its origin in this enrichment process. ? The mantle houses metals that, had they not arrived late, should be in the Earth’s core. In addition, volcanoes emanate gases with anomalies characteristic of chondritic meteorites ,? says Trigo.
This is how the “oasis” of life was formed
Researchers go further and believe that the “late great bombardment” was key to cchange the fate of the Earth, a planet that 3.9 billion years ago was not suitable for life. Although the luminous surface of the Sun was in that period 30% smaller than at present, the ultraviolet radiation flux that it emitted towards the Earth was much greater.
“Due to this flow of a young Sun, a terrestrial atmosphere rich in molecular nitrogen would have been unstable. This circumstance, together with the great impact that gave rise to the Moon, suggests that the Earth could lose, perhaps several times, its atmosphere” , explains Javier Martín Torres, who works at the Astrobiology Center, a joint center of the CSIC and the National Institute of Aerospace Technology. “The arrival of such compounds, and of catalytic metal particles capable of synthesizing more complex organic molecules under the influence of solar radiation,allowed to turn our planet into the only oasis of life that, for now, we know“conclude the study authors.
