Seismology is a powerful tool for probing planetary interiors, and provides us with information on planetary evolution and material properties under high pressure and high temperature. However, seismology has been considered inapplicable to tectonically inactive planets. We, however, show that the atmospheres of solid planets are capable of exerting dynamic pressure on their surfaces, thereby exciting free oscillations with amplitudes that are large enough to be detected by broad-band seismographs. An order-of-magnitude estimate gives amplitudes of a few nanogals for the Earth, Venus and Mars despite the widely varying ambient conditions. The amplitudes are predicted to have weak frequency dependence. Continuous excitations of the Earth's free oscillations having the features predicted by our above theory have recently been confirmed by observations. Seismology promises to provide us with the internal structure of Venus and Mars. [References: 11]
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