The theory that life evolved in soil is appealing because soil traps water between the grains of clay, providing an array of microscopic reaction chambers.[1] These may also promote formation of organic compounds by mechanisms demonstrated in the Urey-Miller experiment, so that planetary surfaces were covered with carbonaceous chondrite. Clayey and organic soils are protected from erosion and thus continued to produce clay and organic matter. Unicellular life, when it evolved, would also have served same purpose of binding the soil.