Oxygen Has Been Directly Detected in Venus’ Dayside Atmosphere


A group of astronomers has recently detected clear signs of atomic oxygen suspended above the toxic clouds of Venus on the daytime side (illuminated by the Sun). This discovery, disclosed by researchers from the German Aerospace Center, may usher in a new chapter in the study of planetary atmospheres. Derived from the analysis of data collected by the Stratospheric Observatory for Infrared Astronomy (SOFIA), it suggests the presence of previously unknown chemical and dynamic processes on the second planet of the solar system.

By exploring the characteristics of the Venusian atmosphere, scientists aim to decipher the mechanisms that have led to its extreme divergence from Earth. Heinz-Wilhelm Hübers, a physicist at the German Aerospace Center (DLR), is the lead author of the most recent study, which appears in Nature Communications.

Atomic oxygen, a singular element unbound to other atoms, differs from diatomic oxygen, the form we breathe on Earth. On Venus, the presence of atomic oxygen had already been confirmed on the nighttime side, where it is less likely to react with other elements or solar light.

Hübers’ team’s discovery lies in detecting this atomic oxygen on the daytime side of Venus, where intense sunlight typically favors the formation of more complex molecules. The data collected by SOFIA not only confirmed this presence but also showed that atomic oxygen is distributed more widely throughout the Venusian atmosphere than previous models suggested.

This observation indicates that the processes generating and dispersing atomic oxygen are active and efficient, even under direct solar radiation. This implies the existence of previously unknown or underestimated atmospheric mechanisms, certainly playing a role in the thermal and chemical regulation of Venus’s atmosphere.

Revealing Venusian Winds

Hübers and his team analyzed data obtained by the Stratospheric Observatory for Infrared Astronomy (SOFIA), operating at high altitude in Earth’s atmosphere and capturing frequencies in the terahertz spectrum at the boundary between microwaves and far-infrared. During three distinct flights, the device gathered information on 17 areas of Venus: 7 in broad daylight, 9 during Venusian night, and 1 at the boundary between the two.

In each of these 17 sites, the presence of atomic oxygen was observed, with maximum concentrations around 100 kilometers above sea level. This zone is precisely between two predominant atmospheric currents on Venus: the super-rotating current below 70 kilometers, moving faster than planetary rotation, and the current extending from the subsolar point to the antisolar point above 120 kilometers.

Absorption spectrum of atomic oxygen on Earth and Venus.
Absorption spectrum of atomic oxygen on Earth and Venus. Image: Hübers et al., 2023.

The researchers suggest that oxygen originates from solar energy breaking down carbon monoxide and carbon dioxide molecules. They also contend that the powerful winds in the Venusian atmosphere are what move these atoms to the planet’s dark side. Once there, they likely combine into molecular oxygen and also react with other elements.

It is important to note that the extremely swift winds on Venus play a dynamic role in the distribution of atomic oxygen across the planet. Blowing at speeds of up to 700 kilometers per hour, they create an atmospheric bridge between day and night, carrying atomic oxygen from the sunlit side to the dark side. This perpetual movement is essential for cooling the Venusian atmosphere.

Map of the location, temperature and density of atomic oxygen on Venus
Map of the location, temperature and density of atomic oxygen on Venus. Image: Hübers.

Indeed, as the researchers explained, there is an energy transfer when single oxygen atoms strike carbon dioxide molecules. This energy is then emitted as radiation, leading to the cooling of the upper layers of the atmosphere. This process is particularly significant as Venus has one of the highest surface temperatures among all planets in the solar system, primarily due to intense greenhouse effects (464 degrees Celsius).

Understanding this cooling mechanism is crucial for modeling the Venusian atmosphere and could shed light on similar phenomena that may occur on other planets. The authors conclude: “With measurements of atomic oxygen in the atmospheres of Earth and Mars, this data could help improve our understanding of how and why the atmospheres of Venus and Earth are so different.”