Mars' Polar Night Skies Alight with Green Glow, ESA Study Reveals

When future astronauts explore the polar regions of Mars, they will see a green glow illuminating the night sky. - THAT

The European Space Agency's (ESA) ExoMars Trace Gas Orbiter (TGO) mission has made a groundbreaking discovery in the Martian atmosphere. For the first time, a visible green glow, similar to the one observed on Earth, has been detected in the night sky of Mars. This finding, published in Nature Astronomy, provides a significant insight into the atmospheric dynamics of the Red Planet.

The green glow, observed in the Martian atmosphere, is a result of a natural phenomenon where oxygen atoms combine to form oxygen molecules about 50 kilometers above the planet's surface. This process, occurring under the cloak of Martian nights, is similar to what happens in Earth's atmosphere, and its detection on another planet marks a milestone in space exploration.

Interestingly, these oxygen atoms embark on a unique journey. They originate on the daytime side of Mars, where sunlight energizes carbon dioxide molecules, causing them to split and release oxygen atoms. As these atoms migrate to the planet's night side, away from the sun's excitation, they regroup at lower altitudes, emitting light and creating the observed glow.

Lauriane Soret, a researcher at the University of Liege and a member of the team responsible for this discovery, explains that the emission results from the recombination of oxygen atoms created in the Martian atmosphere. These atoms are transported by winds to higher altitudes, particularly in the winter latitudes, contributing to the observed night glow.

The intensity of this glow is significant enough to illuminate Martian paths, akin to how moonlit clouds brighten Earth's night skies. Jean-Claude Gérard, lead author of the study and a planetary scientist at the University of Liege, highlights the unexpected and intriguing nature of these observations, underscoring their importance for future Martian exploration.

The discovery builds on previous findings from the Mars Express mission, which detected night glow in infrared wavelengths a decade ago. The TGO further expanded this understanding by detecting bright green oxygen atoms above Mars' daytime side in 2020, a first-time observation for a planet other than Earth.

Orbiting Mars at an altitude of 400 kilometers, the TGO used its ultraviolet-visible channel on the NOMAD instrument to observe the planet's night side. This instrument, covering a spectral range from near-ultraviolet to red light, was specifically oriented to better view the Martian upper atmosphere. NOMAD's experiment is a collaborative effort led by the Royal Belgian Institute for Space Aeronomy, with contributions from teams in Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University), among others.

The nocturnal glow not only serves as a fascinating visual phenomenon but also as a crucial indicator of atmospheric processes. It provides valuable insights into the composition and dynamics of an otherwise hard-to-measure region of the Martian atmosphere, revealing details about oxygen density and how energy is deposited by both sunlight and the solar wind.

Understanding the properties of Mars' atmosphere is vital, not only from a scientific perspective but also for future missions to the Red Planet. The atmospheric density, for example, directly affects the resistance experienced by orbiting satellites and the performance of parachutes used in landing probes on the Martian surface.

It's important to note that this night glow is different from auroras, another form of atmospheric illumination. Auroras, observed both on Mars and Earth, result from energetic electrons from the Sun colliding with the upper atmosphere. They vary spatially and temporally, unlike the more homogeneous night glow.

In conclusion, this discovery by ESA's ExoMars Trace Gas Orbiter marks a significant advancement in our understanding of Martian atmospheric phenomena. As humanity prepares for future exploration of the Red Planet, findings like these illuminate the path forward, both literally and figuratively.