Water on earth: What if it had arrived later than we thought?
Illustration of the great late bombardment on earth. © Nasa's Goddard Space Flight Center/Conceptual Image Lab
The appearance of life on earth has been dependent on three essential elements: liquid water, organic chemical elements called chnops (carbon, hydrogen, etc.) and the source of energy that is the sun the sun . From there, without anyone knowing how, the “magic” has operated and a very primitive life, made up of procedural bacteria (organisms without nucleus), formed. One of our very recent articles thus reported that the Bennu asteroid had, at the dawn of the solar system, water in large quantities and these famous organic elements at the base of the living.
Arrival of water on earth: an unanswered question
The subject of the precise advent of water on earth is very debated within the community of experts. Meteoritic origin? Cometary? Native? We still don't know very well, but A new study Bring a bell sound quite different from the scenario usually envisaged.
“The period in which water has been delivered to the earth is a major question unanswered in planetary sciencessaid Katherine Bermingham, associate professor in the Department of Earth Sciences and Planets of the Rutgers School of Arts & Sciences and the main author of the study. By discovering the answer, we can better understand when and how life has developed. ”
Meteorites and terrestrial rocks in indices
Meteorite sample, known as Campo del Cielo, from which geologists have analyzed the isotope of Molybdenum. © Katherine Bermingham
Geologists have chosen to take the molybdenum as a comparison, present in terrestrial rocks as in meteorites. They selected a group of meteorites from the internal solar system, therefore rather dry because of the heat of the sun, as opposed to those formed in the external system, richer in water.
Then these scientists chose rocks of Greenland, South Africa, Canada, the United States and Japan, which we generally consider that the Molybdène formed during the impact period with Théia, which gave birth to the moon. It was during this phase, about 4.4 billion years ago, that the team wanted to seek the origins of earthly water.
View of the impact of the impact of two planetsimals, like Theia on primitive earth. © NASA / JPL-CALTECH / T. Pyle (SSC)
Water on earth would have been brought after the impact with Théia
Their results of analyzes show that terrestrial rock samples are much closer to the meteorite group of the internal solar system than external, therefore dry. Sign according to them that the event giving birth to the Moon is not the one who brought quantities of water to earth.
“Our results suggest that the moon training event was not a major supplier of water, contrary to what was thought beforesaid Ms. Bermingham. These results nevertheless make it possible to add a small amount of water after the final formation of the nucleus, during what is called late accretion. ”
This study therefore goes in the direction of water which would have been brought to the earth certain types of meteorites, even comets, therefore later than according to other hypotheses.
