NASA Prepares 2025 Carruthers Mission to Explore Earth’s Hidden Hydrogen Halo

To observe the thin hydrogen halo or geocorona of the Earth, NASA is preparing the Carruthers Geocorona Observatory. The observatory will start with NOAA and NASA partner payloads as early as September 2025, capturing the light of ultraviolet light that is produced by hydrogen atoms that constitute the outermost layer of our atmosphere. This is a very elusive area that should be understood as a form of protecting satellites, planning manned missions, and also how planets lose water to space.

Why the Geocorona Matters

According to NASA, the geocorona is approximately 300 miles (480 km) above the surface of the Earth and could be as close to the moon as halfway. Hydrogen atoms in this case reflect sunlight into a faint ultraviolet light that was initially photographed in Apollo 16. This boundary reacts with the solar radiation and charged particles, which affects the functioning of spacecrafts, and also exposes the manner in which the Earth maintains its atmosphere in comparison to other planets like Mars. The process of hydrogen escape also has an informational impact on the search for habitable exoplanets.

Mission Plan and Technology

Named for pioneering astrophysicist George Carruthers, the 240-kilogram spacecraft carries two ultraviolet imagers: a wide-field camera to map the geocorona's vast extent and a near-field sensor for fine detail. It will travel to the Sun-Earth Lagrange Point 1, about a million miles sunward, sharing a Falcon 9 launch with NASA's IMAP and NOAA's SWFO-L1 missions. After a four-month cruise and checkout, a two-year science phase will begin in early 2026. By coupling precise ultraviolet measurements with solar-wind monitoring, the mission will reveal how solar activity shapes Earth's invisible halo.