A green luminescence has been identified in the nocturnal atmosphere of Mars for the first time. This soft green light marvel is visible to the naked eye and was captured by the European Space Agency's (ESA) ExoMars mission while circling the Red Planet.
Nightglow on Earth as seen from the International Space Station.
Unexpected Martian Nightglow
In the polar regions of Mars, the luminosity is so pronounced that it may serve as a navigational aid for human explorers on clear, cloud-free nights, according to Jean-Claude Gérard, a planetary scientist at the University of Liège in Belgium, expressing surprise and anticipation for future missions.
Nightglow, a recurring phenomenon in the Solar System's atmospheres, results from various factors, with the Sun being a prominent source of light emission in Earth's atmosphere. Sunlight-induced photodissociation during the day leads to the splitting of molecules. On the night side, away from the Sun's harsh radiation, loose atoms recombine into molecules, releasing excess energy as photons.
While Earth's nightglow is observable from space with layers of green, golden, and reddish light, the spectacle is less pronounced on other planets. Venus exhibits infrared nightglow, Jupiter's glow is more ultraviolet and variable, and on Mars, both infrared and ultraviolet nightglow have been documented. Additionally, dayglow on Mars, caused by the absorption and release of solar energy in the visible spectrum, has been observed.
Despite these findings, visible nightglow had not been observed on Mars until now. Researchers discovered visible nightglow at Mars' south pole, between altitudes of 40 and 60 kilometers, during its winter. This luminosity results from oxygen atoms transported from the sunlit Martian day combining into dioxygen (O2), emitting a sufficiently bright glow visible from the ground.
This groundbreaking revelation challenges previous assumptions and adds a new dimension to our understanding of Martian atmospheric dynamics, with potential implications for future exploration.
Martian Nightglow Gives Key Insights into Its Atmosphere, Habitability, and Exploration
The recent revelation of visible nightglow on Martian atmosphere holds significant scientific implications, offering insights into its atmospheric chemistry, circulation, and processes. Mars possesses a notably thin atmosphere, and studying its composition aids in understanding the reasons behind its scarcity and the mechanisms governing its dispersion.
Deciphering the atmospheric dynamics of Mars contributes to our comprehension of planetary habitability, comparing worlds like Earth to those with less favorable conditions.
This knowledge is particularly valuable for scientists seeking habitable exoplanets beyond our solar system. Additionally, understanding Mars' atmospheric behavior is crucial for the benefit of future explorers planning missions to the Red Planet.
The researchers suggest that the observed oxygen (O2) nightglow on Mars could be observed not only from Martian orbiters but also with the naked eye from the Martian surface under clear sky conditions.
These findings, published in the journal Nature Astronomy, open the door to future global observations of Martian atmospheric circulation using simpler and more cost-effective instruments, marking a significant step forward in our understanding of the Martian atmosphere.
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