Small flashes of reflected light—called glints—are found in images taken by spacecraft observing the Earth, and occur due to specularly reflected solar radiation. These glints have been found over both ocean and land. Using Deep Space Climate Observatory observations, we show that glints over land are due to specular reflection off horizontally oriented ice platelets floating in the air, while glints over ocean have contributions from reflection off either platelets floating above the ocean or a relatively smooth ocean surface. We use a radiative transfer model to simulate different kinds of glints and to explore their properties. This technique of comparing observations of terrestrial glints with model simulations may provide new information relevant to atmospheric dynamics and the search for habitable exoplanets.