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Water Beyond Earth

The search for water across the Solar System and the galaxy is also the search for life.

Water is not unique to Earth. Astronomers have found evidence of water in many places across the universe — from icy moons to the atmospheres of distant exoplanets.

Water in Our Solar System

Mars
Ice caps at poles contain water ice. Subsurface brines and ancient riverbeds suggest Mars once had liquid water on its surface billions of years ago.
Europa (Jupiter’s Moon)
A global ocean of liquid water lies beneath its icy crust — possibly containing more water than all of Earth’s oceans combined. A prime target in the search for extraterrestrial life.
Enceladus (Saturn’s Moon)
Water vapor geysers erupt from its south pole. Cassini spacecraft detected organic molecules and hydrogen in the plumes — signs of a potentially habitable subsurface ocean.

Water in the Galaxy

Water has been detected in the atmospheres of many exoplanets using telescopes like Hubble and James Webb Space Telescope (JWST). The presence of water vapor is considered a key biosignature in the search for potentially habitable worlds.

Notable Discoveries
  • • WASP-96b — Clear water signature
  • • K2-18b — Water vapor in habitable zone
  • • TRAPPIST-1 system — Multiple Earth-sized planets
Why it matters
Liquid water is essential for life as we know it. Finding it elsewhere increases the probability that life exists beyond Earth.