Astronomers have found direct evidence of the presence of atomic oxygen floating above the toxic clouds of our ‘evil’ neighboring planet.
In our solar system we find two strikingly similar planets: Earth and Venus. They probably share the same age, have similar sizes and most likely formed from the same building blocks. Nevertheless, these celestial bodies show significant differences. For example, Earth has clear, blue skies and an oxygen-rich atmosphere. At the same time, Venus is surrounded by a dense cloud of carbon dioxide, nitrogen and various trace gases. But oxygen can also be found in the turbulent atmosphere of our ‘evil’ twin sister, researchers now show.
Atomic oxygen
Just to clarify: we are talking about a different form of oxygen than that found on Earth. In the case of Venus it is atomic oxygen. “Atomic oxygen consists of only one oxygen atom,” explains researcher Heinz-Wilhelm Hübers in conversation with Scientias.nl out. “So this is different from molecular oxygen, which consists of two oxygen atoms and which we need to breathe.”
Study
The researchers detected this atomic oxygen using the terahertz spectrometer upGREAT on board SOFIA (see box). After analyzing the collected data, they discovered clear signs of atomic oxygen on both the day and night sides of the planet.
More about SOFIA
SOFIA stands for Stratospheric Observatory for Infrared Astronomy. It is an observatory on board a modified Boeing 747SP aircraft used for astronomical observations in the infrared range. SOFIA rises into the stratosphere, where it rises above much of the water vapor in Earth’s atmosphere, giving it a clearer view of the universe.
The discovery is special. “To date, atomic oxygen has not yet been observed on the dayside of Venus,” says Hübers. “However, according to models, it should exist and be generated under the influence of solar radiation. Our measurements confirm this prediction. Furthermore, the results show that the concentration of atomic oxygen decreases as solar radiation decreases. The winds on the dayside transport the atomic oxygen to the nightside, where it then accumulates locally.”
Dayside
It means that atomic oxygen can be found on both the day and night sides of Venus. And this has now been measured directly for the first time. Although we know that atomic oxygen plays a crucial role in the photochemistry and energy balance of Venus’ atmosphere, it has not previously been observed directly on the dayside of Venus. Previous observations of the nightside were limited to studying Venus’ faint skyglow, a subtle emission of light through the planet’s atmosphere.
How does it arise?
How atomic oxygen on Venus actually sees the light of day? This form of oxygen is produced on the dayside of Venus by the breakdown of carbon dioxide (CO2) and carbon monoxide (CO) and is then transported to the nightside. “The atomic oxygen is formed by photolysis,” Hübers explains when asked. “Solar radiation breaks down CO2 molecules, and the oxygen from these CO2 molecules is released as atomic oxygen (this also happens to a much smaller extent with CO).” The team examined 17 points on both sides of the planet and found that oxygen was detected at all locations, with the highest concentrations about 100 kilometers above the surface.
Winds
It is not surprising that it accumulates here. There are two strong air movements in the atmosphere of Venus: below an altitude of 70 kilometers, winds with hurricane force blow against the direction of Venus’ rotation, while above an altitude of 120 kilometers, powerful winds follow the direction of rotation. Between these conflicting atmospheric currents is the layer of atomic oxygen. The temperature of atomic oxygen ranges from about -120 degrees Celsius on the day side to -160 degrees Celsius on the night side. Its concentration is about ten times lower than in the Earth’s atmosphere.
Better understanding
The detection of atomic oxygen in the turbulent Venusian atmosphere is a major step forward. “Our measurements contribute to a deeper understanding of the photochemistry of the Venus atmosphere,” Hübers explains. “In addition, they show that atomic oxygen can serve as a tracer for wind movements at an altitude of about 100 kilometers. Existing models can also be confirmed and further refined thanks to our measurements.”
Venus
At the same time, the study also further expands our knowledge about our still-mysterious neighboring planet. “For example, we now better understand how much atomic oxygen is produced on the dayside of Venus and how this is related to radiation from the sun shining on Venus,” says Hübers. So we’re slowly starting to learn more about Venus, which is still less well studied than our other closest neighbor Mars.
Differences
Ultimately, the researchers hope to figure out how Venus and Earth, despite their strong similarities, took such different paths and are so different today. While we don’t know exactly how Venus and Earth took such divergent paths, research into our neighboring planet may provide us with insight. Was Venus once on the same course as Earth and took a wrong turn somewhere? Or was it our planet’s evil twin from the start?
More about Venus
Venus shows similarities with Earth in many ways. Although the planet has approximately the same size, structure, mass and density, as mentioned, that is where the similarities end. Venus is plagued by an extremely enhanced greenhouse effect, with its thick atmosphere trapping all the heat and surface temperatures rising to 465 degrees Celsius. Furthermore, the planet is surrounded by a cloud cover infused with corrosive sulfuric acid. However, experts believe this has not always been the case. Many scientists suspect that Venus was originally more Earth-like and may even have harbored water. If this is true, the big question arises as to what caused the planet to take such a different path at one point and become so divergent from Earth today.
Understanding Venus’ atmosphere can help us understand its contrasts with Earth. And one of the methods to achieve this is to follow the oxygen trails. “The levels of atomic oxygen in Earth’s atmosphere differ greatly from those on Venus,” says Hübers. “This is because on Earth, atomic oxygen is produced by the dissolution of molecular oxygen, which is essential for life. Research into atomic oxygen can therefore contribute to a deeper understanding of the history of both atmospheres.”
In addition, hopes are also placed on several upcoming space missions to Venus. In recent years, few space probes have headed to Venus. But fortunately that will change soon. Not only NASA returns – the US agency is sending no fewer than two space probes to our nearest neighbor – too the European Space Agency is treating our ‘sister’ to a visit. They promise to be exciting and interesting missions that will ultimately create a global picture of our sister planet and characterize it from top to bottom. And in doing so, we will most likely learn much more about the still enigmatic planet Venus.
