The Earth is one of those extremely rare, special places in the Universe where water can exist, stably, as a liquid. So much of it exists here on Earth, that if you were to add up all the oceans on Earth together, it would weigh more than 10^18 tonnes, more massive than the biggest asteroid ever, and about as massive as Pluto’s giant moon, Charon.

But water only has a very small window in which it can be a liquid. For instance, if you took some warm water up to a very high elevation, it would start to boil, and become a gas! The higher up you took it, the lower and lower your boiling point would be. Read more

PASADENA, Calif. — Using data from the Herschel Space Observatory, astronomers have detected for the first time cold water vapor enveloping a dusty disk around a young star. The findings suggest that this disk, which is poised to develop into a solar system, contains great quantities of water, suggesting that water-covered planets like Earth may be common in the universe. Herschel is a European Space Agency mission with important NASA contributions.

Scientists previously found warm water vapor in planet-forming disks close to a central star. Evidence for vast quantities of water extending out into the cooler, far reaches of disks where comets take shape had not been seen until now. The more water available in disks for icy comets to form, the greater the chances that large amounts eventually will reach new planets through impacts. Read more

There’s a whole lot of water on Earth! Something like 326,000,000,000,000,000,000 gallons (326 million trillion gallons) of the stuff (roughly 1,260,000,000,000,000,000,000 liters) can be found on our planet. This water is in a constant cycle — it evaporates from the ocean, travels through the air, rains down on the land and then flows back to the ocean.

The oceans are huge. About 70 percent of the planet is covered in ocean, and the average depth of the ocean is several thousand feet (about 1,000 meters). Ninety-eight percent of the water on the planet is in the oceans, and therefore is unusable for drinking because of the salt. About 2 percent of the planet’s water is fresh, but 1.6 percent of the planet’s water is locked up in the polar ice caps and glaciers. Another 0.36 percent is found underground in aquifers and wells. Only about 0.036 percent of the planet’s total water supply is found in lakes and rivers. That’s still thousands of trillions of gallons, but it’s a very small amount compared to all the water available. Read more

The oceans, atmosphere, continents and cryosphere are part of Earth’s tightly connected climate system. The ocean’s role in the climate system involves the transport, sequestration , and exchange of heat, fresh water, and carbon dioxide (CO 2 ) between the other components of the system.

When waters descend below the ocean surface, they carry with them dissolved atmospheric gases. The time-dependent tracers in the oceans provide information on which waters have been in contact with the atmosphere on various timescales. They also give information on the ocean circulation and its variability.

The timescale information is needed to understand and to assess the ocean’s role in climate change, and its capacity to take up human-derived constituents, such as CO 2 from the atmosphere. Thus, the advantage to using tracers for ocean circulation studies is the added dimension of time: their time history is fairly well known; they are an integrating quantity; and they provide an independent test for time integration of models and biogeochemical processes. Read more