It is generally accepted that the inner region of the early solar system was subjected to an intense period of meteoric bombardment called late heavy bombardment. However, the researchers found evidence to suggest that this period occurred slightly earlier than previously thought and was less intense but also more prolonged. Such details about this period could influence theories about early Earth and the dawn of life.
About 4 billion years ago, the solar system was far less hospitable than we find it now. Many of the great bodies we know and love were present, but they probably looked remarkably different, especially Earth. We know from a number of sources, including ancient meteorites and planetary geology, that there have been many more collisions and impacts from asteroids originating in the Mars-Jupiter asteroid belt during this period.
Knowledge of these events is especially important to us, as the time period in question is not only when the surface of our planet was taking on a more recognizable shape, but it was also when life had just begun. With more accurate details of Earth̵
“Meteorites provide us with the first history of ourselves,” said Professor Yuji Sano of the Atmosphere and Ocean Research Institute at the University of Tokyo. “This is what fascinated me about them. By studying the properties, such as radioactive decay products, of meteorites that fell to Earth, we can deduce when they arrived and where they came from. For this study we looked at meteorites that came from Vesta, the second largest asteroid after the dwarf planet Ceres. “
Sano and his team found evidence that Vesta was hit by multiple impacted bodies from about 4.4 billion to 4.15 billion years ago. This is prior to 3.9 billion years ago when Late Heavy Bombardment (LHB) is thought to have occurred. Current evidence for the LHB comes from lunar rocks collected during the Apollo moon missions of the 1970s, as well as from other sources. But these new studies are improving on previous models and will pave the way for an updated database of early solar impact records.
“The fact that the meteorites of Vesta origin clearly show us the impacts before the LHB raises the question, ‘Did the heavy late bombardment really occur?'” Sano said. “It appears to us that the first impacts of the solar system peaked before the LHB and gradually diminished over time. It may not have been the catastrophic period of chaos described by current models.”
The abundance of water in asteroid fragments
Mizuho Koike et al. Evidence of early asteroid collisions before 4.15 Ga from the basaltic history of eucrite phosphate U – Pb, Science letters of the earth and planets (2020). DOI: 10.1016 / j.epsl.2020.116497
Meteorite Study Casts Popular Theory About Early Solar System (2020, Sept. 16)
recovered on September 16, 2020
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