Modern theory from ancient impacts
Meteorite study calls into doubt a popular theory about the early solar
system

Date:
September 16, 2020
Source:
University of Tokyo
Summary:
It is generally accepted that the inner region of the early solar
system was subject to an intense period of meteoric bombardment
referred to as the late heavy bombardment. However, researchers have
found evidence that suggests this period occurred slightly earlier
than thought and was less intense but also more prolonged. Such
details about this period could impact theories about the early
Earth and the dawn of life.



FULL STORY ========================================================================== Around 4 billion years ago, the solar system was far less hospitable than
we find it now. Many of the large bodies we know and love were present,
but probably looked considerably different, especially the Earth. We
know from a range of sources, including ancient meteorites and planetary geology, that around this time there were vastly more collisions between,
and impacts from, asteroids originating in the Mars-Jupiter asteroid belt.


========================================================================== 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 form, but was also when life was just
getting started. With more accurate details of Earth's rocky history,
it could help researchers answer some long-standing questions concerning
the mechanisms responsible for life, as well as provide information for
other areas of life science.

"Meteorites provide us with the earliest history of ourselves," said
Professor Yuji Sano from the Atmosphere and Ocean Research Institute
at the University of Tokyo. "This is what fascinated me about them. By
studying properties, such as radioactive decay products, of meteorites
that fell to Earth, we can deduce when they came and where they came
from. For this study we examined 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 impacting bodies around
4.4 billion to 4.15 billion years ago. This is earlier than 3.9 billion
years ago, which is when the 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 other sources. But these new studies are improving upon previous models and will
pave the way for an up-to-date database of early solar impact records.

"That Vesta-origin meteorites clearly show us impacts earlier than
the LHB raises the question, 'Did the late heavy bombardment truly
occur?'" said Sano.

"It seems to us that early solar system impacts peaked sooner than the
LHB and reduced smoothly with time. It may not have been the cataclysmic
period of chaos that current models describe."

========================================================================== Story Source: Materials provided by University_of_Tokyo. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Mizuho Koike, Yuji Sano, Naoto Takahata, Tsuyoshi Iizuka,
Haruka Ono,
Takashi Mikouchi. Evidence for early asteroidal collisions prior to
4.15 Ga from basaltic eucrite phosphate U-Pb chronology. Earth
and Planetary Science Letters, 2020; 549: 116497 DOI:
10.1016/j.epsl.2020.116497 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200916094247.htm

--- up 3 weeks, 2 days, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)