NASA's new mission aims to photograph a natural phenomenon that is normally impossible to observe: a faint glow surrounding the Earth, marking the outermost boundary of the atmosphere. This region, called the "exosphere," emits light that changes its structure depending on solar activity. Understanding the behavior of this layer is crucial for predicting space conditions near Earth, and this information is seen as a critical step in ensuring the safety of Artemis astronauts who will travel to the Moon and Mars in the future.
Exploring Earth's Invisible Boundary:
In the early 1970s, scientists had very little evidence about how far Earth's atmosphere extended into space. The main uncertainty focused on the exosphere, the outermost layer starting about 500 kilometers above the surface. Experts believed this layer mainly consisted of hydrogen atoms, which are high enough to escape Earth's gravity.
The exosphere can only be detected through a very weak ultraviolet glow called the "geocorona." Pioneer scientist Dr. George Carruthers developed special ultraviolet cameras to directly observe this glow. In April 1972, Apollo 16 astronauts placed Carruthers' camera on the lunar surface, capturing the first images of Earth's geocorona.
Viewing Earth in a New Light:
Today, scientists believe the exosphere extends at least halfway to the Moon. However, its significance is not only in its size. When solar flares reach Earth, they first encounter the exosphere, which can trigger dangerous space weather events. Studying how the exosphere reacts to these changes will help reduce risks for astronauts and spacecraft. This region also plays a role in the gradual loss of hydrogen, the primary component of water (H2O). Tracking how hydrogen escapes Earth could provide insights into how our planet preserves water and might also help in the search for habitable exoplanets.
Journey to L1:
The observatory named after George Carruthers is about the size of a love seat and weighs 240 kilograms. The spacecraft was launched along with NASA's IMAP and NOAA's SWFO-L1 satellites. All missions are en route to the Lagrange 1 (L1) point, where the gravitational balance between the Sun and Earth is maintained, for a four-month journey.
Carruthers' observatory will begin its two-year scientific phase in March 2026, capturing the first uninterrupted films of the exosphere. Observations from L1, which is four times farther than the Moon, will map the movement of hydrogen atoms in the exosphere and the processes by which they escape into space.
The collected data will not only enhance our understanding of Earth but also contribute to the study of exoplanet atmospheres and their potential for habitability.
