- 3389 - METEORITES - remnants of early solar system? Meteorites are remnants of the building blocks that formed Earth and the other planets orbiting our Sun. Analysis of their isotopic makeup settles a longstanding debate about the geochemical evolution of our Solar System and our home planet.
--------------------- 3389 - METEORITES - remnants of early solar system?
- In their youth, stars are surrounded by a rotating disk of gas and dust. Over time, these materials aggregate to form larger bodies, including planets. Some of these objects are broken up due to collisions in space, the remnants of which sometimes hurtle through Earth's atmosphere as meteorites.
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- By studying a meteorite's chemistry and mineralogy details we can learn about the conditions these materials were exposed to during the Solar System's tumultuous early years. Of particular interest is why so-called moderately volatile elements are more depleted on Earth and in meteoritic samples than the average Solar System, represented by the Sun's composition. They are named “volatiles” because their relatively low boiling points mean they evaporate easily.
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- The periods of heating and cooling resulted in the evaporation of volatiles from meteorites. Solving the mystery involved studying a particularly primitive class of meteorites called “carbonaceous chondrites” that contain crystalline droplets, called “chondrules“, which were part of the original disk of materials surrounding the young Sun.
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- Because of their ancient origins, chondrule beads are an excellent laboratory for uncovering the Solar System's geochemical history. Understanding the conditions under which these volatile elements are stripped from the chondrules can help us work backward to learn the conditions they were exposed to in the Solar System's youth and all the years since.
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- Each element contains a unique number of protons, but its “isotopes” have varying numbers of neutrons. This means that each isotope has a slightly different mass than the others. As a result, chemical reactions discriminate between the isotopes, which, in turn, affects the proportion of that isotope in the reaction's end products.
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- How and when in their lifespans do the chondrules lose their volatiles? The isotopic record indicates that the volatiles were stripped as a result of massive shockwaves passing through the material circling the young Sun that likely drove melting of the dust to form the chondrules.
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- These types of shockwave events can be generated by gravitational instability or by larger baby planets moving through the nebular gas. The revelation that shockwaves modified the material from which the planets were born has major implications for Earth science as well.
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- Once a planet gets as big as ours, its gravity is sufficient that losing most volatile elements becomes very difficult. Knowing that moderately volatile elements were stripped from the planetary building blocks themselves answers fundamental questions about Earth's geochemical evolution.
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December 29, 2021 METEORITES - remnants of early solar system? 3388
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