The rigid outermost shell of a rocky planet, moon, or other celestial body, consisting of the crust and uppermost portion of the mantle. The lithosphere forms the solid surface on which geological processes occur.
From Greek 'lithos' meaning 'stone' and 'sphaira' meaning 'sphere,' coined by geologist A.E.H. Love in 1911. Originally used for Earth, the term expanded to planetary science as we explored other worlds with solid surfaces.
Each planet's lithosphere tells a unique story - Earth's is broken into moving tectonic plates, Mars shows evidence of ancient plate tectonics that stopped billions of years ago, while the Moon's lithosphere is a frozen record of the early solar system's violent bombardment period! Venus has the thickest lithosphere in the inner solar system.
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