Pebbles May Have Created Jupiter and Saturn as Planetary Building Blocks

Planetary pebbles may actually be the building blocks that form the planets of the future. Scientists have unraveled the mystery of how Jupiter and Saturn likely formed.

The largest planets in the solar system probably formed first. Jupiter and Saturn, which are made up mostly of hydrogen and helium, presumably accumulated their gases before the solar nebula dispersed. Observations of young star systems show that the gas disks that form planets usually have lifetimes of only 1 to 10 million years, which means that the gas giant planets in our solar system probably formed within this time frame. In contrast, the Earth probably book at least 30 million years to form, and may have taken as long as 100 million years.

The most widely accepted theory for gas giant formation is called the core accretion model. In this model, a planet-sized core of ice and rock forms first. Then and inflow of interstellar gas and dust attaches itself to the growing planet. Yet in order to accumulate a massive atmosphere, the giatns require solid cores. This means that it would have taken far longer to form the gas giants, even though the likely formed in only a few million years.

Now, researchers have conducted new calculations that show that the cores of Jupiter and Saturn could form well within the 10-million-year time frame if they grew by gradually accumulating a population of planetary pebbles.

'"If the pebbles form too quickly, pebble accretion would lead to the formation of hundreds of icy Earths," said Katherine Kretke, one of the researchers, in a news release. "The growing cores need some time to fling their competitors away from the pebbles, effectively starving them. This is why only a couple of gas giants formed."

The findings reveal a bit more about how the gas giants in our solar system formed. More specifically, it "solves" the time problem seen in other theories.

The findings are published in the journal Nature.

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