Meteors that have crashed to Earth have long been regarded as relics of the early solar system. These craggy chunks of metal and rock are studded with chondrules — tiny, glassy, spherical grains that were once molten droplets. Scientists have thought that chondrules represent early kernels of terrestrial planets: As the solar system started to coalesce, these molten droplets collided with bits of gas and dust to form larger planetary precursors.
However, a new study from scientists at MIT and Purdue University suggests that this may not be the case after all – and we’ve given meteorites too much credit. The researchers have developed a computer simulations program which helped them observe the role of chondrules, and what they’ve seen is that these grains are probably only secondary products. It seems that chondrules have appeared much more recently than planets. The team of scientists suggests that these spherical masses were created by the collision of two small planets, which crashed into each other with such a force that some of their melted material blasted into outer space. These residual rocks would form chondrules after having lowered their temperature.
“This tells us that meteorites aren’t actually representative of the material that formed planets – they’re these smaller fractions of material that are the byproduct of planet formation,” says Brandon Johnson of MIT’s Earth, Atmospheric and Planetary Sciences department. “But it also tells us the early solar system was more violent than we expected: You had these massive sprays of molten material getting ejected out from these really big impacts. It’s an extreme process.”
Results of the simulations supported the new theory that chondrules aren’t as important as previously thought, at least to planet formation.
If confirmed, this study’s results change a lot of what we know about our early solar system and how the planets formed.
“If this finding is correct, then it would suggest that chondrites are not good analogs for the building blocks of the Earth and other planets,” said University of Chicago Associate Professor of Planetary Science, Fred Ciesla. “Meteorites as a whole are still important clues about what processes occurred during the formation of the Solar System, but which ones are the best analogs for what the planets were made out of would change.”
However, not all computer simulations are accurate, and this is going to need some confirmation before it is viewed as a fact, but it casts a big shadow over something which was regarded as a near certainty for the longest of time.
The next step in the research may be to explore how this chondrule formation mechanism fits into a new model for the early stages of planet formation called “pebble accretion,” in which the effect of gas drag from the protoplanetary nebula is important.
Journal reference: http://goo.gl/WZh5WK.