In this illustration of the early solar system, the dashed white line represents the snow line — the transition from the hotter inner solar system, where water ice is not stable (brown) to the outer Solar system, where water ice is stable (blue). Two possible ways that the inner solar system received water are: water molecules sticking to dust grains inside the “snow line” (as shown in the inset) and carbonaceous chondrite material flung into the inner solar system by the effect of gravity from protoJupiter. With either scenario, water must accrete to the inner planets within the first ca. 10 million years of solar system formation.
Credit: Illustration by Jack Cook, Woods Hole Oceanographic Institution
Earth is known as the Blue Planet because of its oceans, which cover more than 70 percent of the planet’s surface and are home to the world’s greatest diversity of life. While water is essential for life on the planet, the answers to two key questions have eluded us: Where did Earth’s water come from and when? While some hypothesize that water came late to Earth, well after the planet had formed, findings from a new study significantly move back the clock for the first evidence of water on Earth and in the inner solar system.