Clues from Space Help Track Freshwater on Earth

Freshwater is essential to life on Earth, but its distribution, patterns of precipitation and origins are still only partially understood. Technologies that allow us to observe water from space help offer new insight into this critical resource.

The volume of Earth's water compared to the size of Earth.

These spheres represent all of Earth’s water, Earth’s liquid fresh water, and water in lakes and rivers. The largest sphere represents all of Earth’s water, and its diameter is about 860 miles (the distance from Salt Lake City, Utah, to Topeka, Kansas). It would have a volume of about 332,500,000 cubic miles. The sphere includes all the water in the oceans, ice caps, lakes, and rivers, as well as groundwater, atmospheric water, and even the water in you, your dog, and your tomato plant. Image Credit: USGS.

The United Nation’s World Water Day is March 22. It’s an international event designed to spread awareness about the critical resource of freshwater: where it is found, how it used, and what we can do to protect it. Essential as water is to life on Earth, many mysteries still remain about its origins, current distribution and future availability. Sometimes the answers to those questions can best be found by taking a step out to consider our planet from the lens of space.

An image of Vesta.

Full view of Vesta. Image Credit: NASA, JPL-Caltech, UCLA, MPS, DLR, IDA

Uncovering Water’s Origins

Where did the water essential to life on our planet come from? Details are still under debate, but evidence suggests that the story of water on Earth actually begins in space. Hydrogen and oxygen are required to make water, and both could be found among the particles that made up the newly formed Earth, but high temperatures and a lack of atmosphere on the newborn planet would likely have caused any water that formed to swiftly evaporate and be lost into space.

Therefore, it was commonly theorized that the water on our planet today was delivered via ice contained in asteroids or comets that collided with Earth sometime after the atmosphere had formed—hundreds of millions of years after the planet began.

In 2014, however, a study published in journal Science suggested that water has been on our planet since times much nearer to its formation. The study by Adam R. Sarafian and others compared hydrogen isotopes from the mineral apatite found in carbonaceous chondrite (remnants of ancient meteorites), rocks on Earth, and the asteroid Vesta, which is believed to have formed around the same time as Earth. The similarity of the isotopic fingerprint from each of the sources suggests that water’s origins on Earth may be considerably earlier than previously believed—perhaps dating back to the planet’s formation.

A satellite image of a storm.

One of the first storms observed by the NASA/JAXA GPM Core Observatory on March 17, 2014, in the eastern United States revealed a full range of precipitation, from rain to snow. Image Credit: NASA

Tracking Today’s Precipitation Patterns

When it comes to studying where water is today, particularly how water moves around the globe in the form of precipitation, taking a view from space can still be helpful. The  observations this time come from closer than an asteroid belt. In the past decade, satellites have increasingly been used to monitor freshwater on the Earth, in particular from the viewpoint of the weather and climate patterns that determine precipitation across the world.

Space agencies use satellite imagery to better understand patterns of precipitation and predict rainfall, prepare for storms, and generally strengthen their knowledge of how the global weather system works.  To help further this, the Global Precipitation Measurement (GPM) mission was launched in 2014. The GPM is a collaboration by NASA and the Japanese Aerospace Exploration Agency (JAXA) to coordinate precipitation measurements from 12 different satellites to create a map that provides more complete global coverage of precipitation than any of its predecessors.  The project draws data from  satellites operated by the U.S. National Oceanic and Atmospheric Administration (NOAA), the European Organisation for the Exploitation of Meteorological Satellites, the U.S Department of Defense Meteorological Program, the Indian Space Research Organization, and the Centre National d’Études Spatiales of France, as well as satellites operated by NASA and JAXA.

The first map created using data from the GPM mission was released in February.

Looking to the Future

Satellites also can provide useful information for projecting future availability and distribution of freshwater. Part of the mission of the SERVIR-Himalaya project begun last year is to improve ability to track and manage freshwater resources. In February, a workshop was held in Pakistan to train participants on how satellite imagery and data can be used for purposes such as forecasting floods and or improving water management policies to help address increased scarcity in water-limited regions.

Freshwater can be a boon, as a necessity for food security, energy production, or for municipal uses, or it can be a threat, in the case of flooding or as a trigger of landslides. In either case, it plays an important role in life, and a better understanding of how the hydrosphere works has the potential to benefit society in numerous ways.

Those who wish to learn more about freshwater on Earth can visit the official World Water Day website.