Asteroid Day Brief Apr 04

How analyzing meteorites led us to learn about the evolution of Jupiter in the early solar system ?

When scientists analyzed over 32 different types of meteorites found on Earth, they realized they could be categorized in two distinct reservoirs: the carbonaceous chondrites and the non-carbonaceous chondrites.

The meteoriticist Paul Warren, looked into measurements of chromium and titanium isotopes in these two types of meteorites. He expected a continuum of isotopic abundance because he was under the assumption that both meteorites had formed in the same region of the asteroid belt. In fact, he found that in the carbonaceous chondrites, the isotopes level were starkly different than in non-carbonaceous chondrites. The first plausible explanation for this phenomenon is that they could have been separated at formation, millions of years apart. However, this theory contradicts what we know about the carbonaceous chondrites, that is, they are younger than other meteorites. According to Dr. William Bottke, director of the Department for Space Studies at the Southwest Research Institute, Colorado US, other theories suggest the CC formed in the asteroid belt. “This could still be true,” he mentioned, when asked about the presence of these asteroids in the asteroid belt, “but then it is unclear how to create a clean separation between the NCC and CC reservoirs.”
Another explanation is that the two reservoirs must have been formed in two different regions of space.

How does this discovery connects to Jupiter ?

The main theory for this separation can be explained by the formation of Jupiter. In order to become a gas giant, Jupiter’s core had to be, at first, a rock body of about 20 times the Earth’s mass. Then the planet started to accrete large amount of gas present in this region of space. Hence over several millions of years, the planet became a gas giant. Once Jupiter was large enough, it led to the separation of the two reservoirs in such a way that they continued to evolve independently from each other. At that moment the CC reservoir, beyond Jupiter, changed its isotopic characteristics due to the presence of dust in space.

How did these two types of asteroids end up together in the asteroid belt ?

Jupiter was actually created where Saturn is located today. As the planet grew it migrated towards the Sun, thus creating movement on its path. This led to the blending of non-carbonaceous and carbonaceous chondrites in the asteroid belt.
This phenomenon is common in planet’s dynamics. Dr. Bottke revealed in a recent paper how comets from the primordial Kuiper belt could have been captured in the asteroid belt during planet migration.

Dr Bottke is also involved with a submitted paper led by Katherine Kretke, which, he said “proposes that many CC bodies in the giant planet zone were placed into the main asteroid belt by a combination of giant planet formation and gas drag from the primordial solar nebula. This model would provide an interesting alternative to implanting CC bodies in the main belt during the so-called Grand Tack model of giant planet migration.”

Finally, pieces of these carbonaceous and non-carbonaceous chondrites asteroids eventually found their way to Earth, providing us with samples of meteorites containing the possible history of our early solar system.

Stay tuned for our next Asteroid Day Briefing.

Reference Article:
http://www.sciencemag.org/news/2018/03/surprising-meteorite-discovery-points-early-solar-system-chaos?utm_campaign=news_daily_2018-03-28&et_rid=17058276&et_cid=1938361

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Photo Credit: NASA/ JPL-Caltech/ T. Pyle