NASA’s Spitzer Space Telescope has discovered that water is abundant in the universe. Scientists have found it in the form of ice or gas around various stars, in the space between stars, and even on a hot, gas planet outside our solar system. Observing water helps scientists understand how water, the essential ingredient to life on Earth, begins to make its way to planets. Scientists use water molecules because they are easier to detect than other molecules. Scientists use water to study the planet-formation process and to study the chemistry and physics of the universe.

About 1,000 light-years away in the constellation Perseus (the Hero), a star-forming region called NGC 1333-IRAS 4B is being watched by Spitzer. It is in a very early stage of development with one stellar embryo and growing in size as it “feeds” off the material of the nebula collapsing around it. The whole star system is growing inside the cool nebulous cocoon of gas and dust. Inside the cocoon is a warm disk of planet-forming materials. Spitzer detected water in the form of vapor coming from the outer nebula and raining onto the planet-forming dusty disk. The disk is where planets form.

Spitzer has detected enough water vapor falling on the disk to fill the oceans on Earth 5 times. Scientists calculated the disk’s density, dimensions, radius, and temperature on NGC 1333-IRAS 4B just by analyzing its water. Water falls as ice from the outer cocoon to its hot, planet-forming disk. The ice vaporizes due to the heat. The vapor refreezes inside the cool disk as asteroids and comets, becoming part of its solar system. Scientists believe water arrived on Earth in the form of icy asteroids and comets.