Info

8k 15

8k 15

4k 3

[rCpCrC + rPpMrP rCpMrC ]

RcX5

RcX5

If we know the material that is likely to make up the mantle and the core, we can estimate pM and Pc- The average density is easily determined, so we can find (RC/RP).

For planets on which we can place seismometers, we can learn about interior activity. We can also learn about how seismic disturbances move through the interior. For example, one Apollo experiment involved allowing a spent Lunar Module to crash into the Moon, going on to measure the seismic disturbances with seismometers that had been left behind. Seismic waves travel at different speeds through different materials. They will also be reflected from boundaries between different materials. Analyzing these waves can tell us about the composition and size of various interior sections.

Additional information comes from the magnetic field, which would require a molten iron core, and some rotation to stir the core. Heat flow measurements can tell us how close radioactive material is to the surface. This tells us whether the mantle is well mixed or differentiated.

In Fig. 24.11 we show the interior structures of the four inner planets. In order to make the

Earth

Mars

Fig 24.11.

Mars

Mercury

Model interiors for the four inner planets. In each case, the sizes are relative to the planet's radius, so the total radius of each planet is the same in this figure.

Venus

Mercury

Model interiors for the four inner planets. In each case, the sizes are relative to the planet's radius, so the total radius of each planet is the same in this figure.

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