ESA’s ExoMars Trace Gas Orbiter has discovered a green nightglow in the Martian atmosphere, providing crucial data on atmospheric processes and potential illumination for future Martian missions. This phenomenon, distinct from auroras, marks a significant advancement in our understanding of MarsMars is the second smallest planet in our solar system and the fourth planet from the sun. It is a dusty, cold, desert world with a very thin atmosphere. Iron oxide is prevalent in Mars' surface resulting in its reddish color and its nickname "The Red Planet." Mars' name comes from the Roman god of war.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Mars.
When future astronauts explore Mars’s polar regions, they will see a green glow lighting up the night sky. For the first time, a visible nightglow has been detected in the Martian atmosphere by ESA’s ExoMars Trace Gas Orbiter (TGO) mission.
Under clear skies, the glow could be bright enough for humans to see by and for rovers to navigate in the dark nights. Nightglow is also observed on Earth. On Mars, it was something expected, yet never observed in visible light until now.
Nightglow on Mars
The atmospheric nightglow occurs when two oxygen atoms combine to form an oxygen molecule, about 50 km (~30 miles) above the planetary surface.
The oxygen atoms have been on a journey: they form on Mars’s dayside when sunlight gives energy to carbon dioxide molecules, making them split apart. When the oxygen atoms migrate to the night side and stop being excited by the Sun, they regroup and emit light at lower altitudes.
“This emission is due to the recombination of oxygen atoms created in the summer atmosphere and transported by winds to high winter latitudes, at altitudes of 40 to 60 km in the Martian atmosphere,” explains Lauriane Soret, researcher from the Laboratory of Atmospheric and Planetary Physics of the University of Liège, in Belgium, and part of the team that published the discovery in Nature Astronomy.
The illumination from the nightglow could be bright enough to light the way of the future see the glow as bright as moonlit clouds on Earth.
“These observations are unexpected and interesting for future trips to the Red Planet,” says Jean-Claude Gérard, lead author of the new study and planetary scientist at the University of Liège.
Follow the Green Glowing Road
The international scientific team was intrigued by a previous discovery made using Mars Express, which observed the nightglow in infrared wavelengths a decade ago. The Trace Gas Orbiter followed up by detecting glowing green oxygen atoms high above the dayside of Mars in 2020 – the first time that this dayglow emission was seen around a planet other than Earth.
These atoms also travel to the nightside and then recombine at lower altitude, resulting in the visible nightglow detected in the new research published today.
Orbiting the Red Planet at an altitude of 400 km, TGO was able to monitor the night side of Mars with the ultraviolet-visible channel of its NOMAD instrument. The instrument covers a spectral range from near ultraviolet to red light and was oriented towards the edge of the Red Planet to better observe the upper atmosphere.
The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy, working with teams from Spain (IAA‐CSIC), Italy (INAF‐IAPS), and the United Kingdom (Open University), among others.
Scientific Value
The nightglow serves as a tracer of atmospheric processes. It can provide a wealth of information about the composition and dynamics of a region of the atmosphere difficult to measure, as well as the oxygen density. It can also reveal how energy is deposited by both the Sun’s light and the solar wind – the stream of charged particles emanating from our star.
Understanding the properties of Mars’ atmosphere is not only scientifically interesting but it is also key for missions to the Red Planet’s surface. Atmospheric density, for example, directly affects the drag experienced by orbiting satellites and by the parachutes used to deliver probes to the Martian surface.
Nightglow Versus Aurora
Nightglow is also observed on Earth, but it is not to be confused with auroras. Auroras are just one way in which planetary atmospheres light up.
Auroras are produced, on Mars as on Earth, when energetic electrons from the Sun hit the upper atmosphere. They vary across space and time, while nightglow is more homogeneous. Nightglow and auroras can both exhibit a wide range of colors depending on which atmospheric gases are most abundant at different altitudes.
The green nightglow on our planet is quite faint, and so is best seen by looking from an ‘edge on’ perspective – as portrayed in many spectacular images taken by astronauts from the International Space StationThe International Space Station (ISS) is a large spacecraft in orbit around the Earth that serves as a research laboratory and spaceport for international collaboration in space exploration. It was launched in 1998 and has been continuously occupied by rotating crews of astronauts and cosmonauts from around the world since 2000. The ISS is a joint project of five space agencies: NASA (USA), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada). It orbits the Earth at an altitude of approximately 400 kilometers (250 miles), and provides a unique platform for scientific research, technological development, and human space exploration.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>International Space Station.
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A timelapse video by European Space AgencyThe European Space Agency (ESA) is an intergovernmental organization dedicated to the exploration and study of space. ESA was established in 1975 and has 22 member states, with its headquarters located in Paris, France. ESA is responsible for the development and coordination of Europe's space activities, including the design, construction, and launch of spacecraft and satellites for scientific research and Earth observation. Some of ESA's flagship missions have included the Rosetta mission to study a comet, the Gaia mission to create a 3D map of the Milky Way, and the ExoMars mission to search for evidence of past or present life on Mars.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>European Space Agency astronaut Tim Peake taken during his six-month Principia mission on the International Space Station. The British astronaut commented on this timelapse: “International Space Station view of an ‘aurora rise’ – spot the two satellites at the end? Timelapse video made from images taken at one second intervals played back 25 times faster.” Credit: ESA/NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>NASA
Reference: “Observation of the Mars O2 visible nightglow by the NOMAD spectrometer onboard the Trace Gas Orbiter” by J.-C. Gérard, L. Soret, I. R. Thomas, B. Ristic, Y. Willame, C. Depiesse, A. C. Vandaele, F. Daerden, B. Hubert, J. P. Mason, M. R. Patel and M. A. López-Valverde, 9 November 2023, Nature Astronomy.
DOI: 10.1038/s41550-023-02104-8
Source: SciTechDaily