But the planetesimal hypothesis has no room for this enormous percentage of carbon-dioxide in the primitive atmosphere.
Such, then, is the mechanism of the first phase in the history of a spiral nebula according to the planetesimal hypothesis.
Let us now inquire briefly into the bearing of this planetesimal hypothesis upon the early geological history of the earth.
Any of innumerable small bodies of accreted gas and dust thought to have orbited the Sun during the formation of the planets. ◇ The theory that explains the formation of the solar system in terms of the aggregation of such bodies is known as the planetesimal hypothesis. According to this theory, first proposed in 1900, the planetesimals formed within a spiral disk of dust and gas surrounding a central nucleus. Their gravitational attraction eventually caused the planetesimals to coalesce into protoplanetary disks from which larger objects such as planets, asteroids, and satellites were formed, while the nucleus coalesced into the Sun.