Formation of the Earth


How did the Earth Get Here?


Clues to the Formation of the Solar System:

Formation of the Earth by accretion:

Initial solar nebula consists of mixtures of grains (rock) and ices. The initial ratio is about 90% ices and 10% grains

The sun is on so there is a temperature gradient in this mixture:

In the inner part of the solar system, only things which exist as a solid at high temperature are available (so how come there is so much water on the earth? -- answer later)

So in the inner part of the solar system you can only make a rocky planet via acretion of grains.

In the outer part of the solar system, ices can exist so you can make larger planets out of the more abundant ices

Jupiter (mostly H and He) formed in a manner similar to the Sun, that is not by accretion. Note that Jupiter can never become a star. A star is a ball of gas sufficiently hot to excite nuclear reactions . The minimum mass require for this is about 8% the mass of the Sun. Jupiter's mass is an order of magnitude below this limit. Jupiter will never be a star.

Jupiter has a large mass and perturbs orbits of objects near them. There were lots of these objects scattered between Jupiter and Pluto.

Jupiter redirected some of this cometary material into the inner solar system and most of the earth's water was delivered through comet bombardment (therefore would we be here without Jupiter?)

Steps in the accretion process:

In the outer part of the solar system, the same 4 step process of accretion occurred but it was accretion of ices (cometisemals) instead of grains.

Things to note about the formation of planets via accretion