Artist's impression of the detection of ozone on Venus' night side
This artist's impression of planet Venus highlights the spots where the molecule ozone (O3) has been detected in the planet's atmosphere. The discovery relies on observations performed with the SPICAV instrument on board ESA's Venus Express.
According to the new data, ozone is located at varying altitudes in the Venusian atmosphere, between 90 and 120 km, and is always confined to a rather thin layer, measuring 5 to 10 km across. The ozone layer on Venus is very tenuous—up to a thousand times less dense than the ozone layer in the Earth's lower stratosphere.
The detection of ozone in Venus' atmosphere was achieved using the stellar occultation method. This technique allows astronomers to indirectly probe a planet's atmosphere by studying its influence on the light from distant stars. A drawback of the method, however, is that it relies on the availability of stars in the spacecraft's line of sight, meaning that it yields an uneven coverage of the planet and is limited to the night side. This means that investigations of the spatial or temporal distribution of ozone across the planet are not straightforward.
The illustration on the lower right angle of the image shows the chemical reaction that gives rise to ozone in planetary atmospheres with large abundance of molecular oxygen (O2). When irradiated by solar ultraviolet rays, oxygen molecules are broken into atoms (O), which may, in turn, react with other oxygen molecules and create ozone.