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Equation 5 · Part 2 · From Origins to Frontier: A History of Planetary Science and Exploration

Symbol g

v=2gr2(ρm−ρs)9ηv = \frac{2 g r^2 (\rho_m - \rho_s)}{9\eta}
gg

What this part means

g occurs above the fraction bar. The numerator is divided by the entire denominator below it.

Its job in the formula

g occurs above the fraction bar. The numerator is divided by the entire denominator below it.

The passage around this formula

…diapirism, iron rain, and turbulent entrainment rather than single isolated blobs — but it exposes the essential dependency: differentiation requires a large enough density contrast, a large enough body (so gravity g and blob size r are non-trivial), and a mantle viscosity η\eta low enough (i.e., hot enough) for sinking to complete within the age of the solar system. This is exactly why small, cold bodies — many asteroids among them — never fully differentiated and instead preserve primitive, unprocessed…

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Learn the underlying idea

A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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