William Atkins
Friday, 06 February 2009 23:21
Science -
Space
Page 3 of 4
Earth, the third planet from the center of our Solar System, has an equatorial radius of around 6,378 kilometers (1.0 Earth-radius), and an eccentricity of about 0.0167.
Mars, the second smallest planet, but the outermost one, of the four inner planets, has an equatorial radius of about 3,396 kilometer (about 0.5 Earth-radius), and an eccentricity of 0.0933 (the second most elliptical of the four planets).
Hansen made a different hypothesis than what is generally given by astronomers. He assumed that the dust coming off the early Sun did not disperse uniformly.
Instead, he thinks it fragmented into bands at various distances from the Sun. He compares it to the
“rings of Saturn.”
Thus, Earth and Venus formed inside one large band ("annulus") of dust. They gathered in large amounts of dust and gas, growing bigger and bigger as they held in most of these newly gained materials.
However, at the same time, they threw off some of these materials.
Some of these expelled off materials came back to collide with the Earth or Venus. However, some of it never came back but, instead, collided with one another and began to form Mercury and Mars.
Hansen explains,
"If this happens, the particles are put on a new orbit. They become decoupled from the main annulus and don't come back." [National Geographic Society]
From this one band (annulus) most of the material formed Earth and Venus—approximately 90%, according to Hensen’s computations.
Page four concludes.
