<img loading="lazy" src="http://www.newscientist.com/data/images/ns/cms/dn21021/dn21021-1_300.webp" align="left" hspace="15" vspace="5" alt="Sunlight breaks up carbon dioxide molecules in Venus's atmosphere, freeing oxygen atoms that meet up on the planet's cooler night side to bind into ozone molecules. Venus Express discovered the ozone molecules by looking at individual background stars through the planet's atmosphere, a technique that yields only spotty coverage (Image: ESA/AOES Medialab)" />
Venus Express found ozone's spectral signature in a layer 100 kilometres up in the planet's atmosphere, at concentrations of no more than 1 per cent those found in Earth's atmosphere.


Sunlight breaks up carbon dioxide molecules in Venus's atmosphere, freeing oxygen atoms that meet up on the planet's cooler night side to bind into ozone molecules. Venus Express discovered the ozone molecules by looking at individual background stars through the planet's atmosphere, a technique that yields only spotty coverage (Image: ESA/AOES Medialab)



Computer models suggest that Venus's ozone is formed when sunlight breaks up carbon dioxide molecules. The oxygen atoms freed in this reaction meet up on the planet's cooler night side to form molecular pairs (O2) and triplets (ozone, or O3).


"The key chemical reactions operating in Earth's upper stratosphere may also operate on Venus," write <a href="http://www.iau.org/administration/membership/individual/12789/" target="_blank" class="news_link">Franck Montmessin</a> of the <a href="http://www.latmos.ipsl.fr/" target="_blank" class="news_link">LATMOS</a> atmospheric research centre in France and his colleagues in a paper describing the results.


Ozone is important for life on Earth because it blocks damaging ultraviolet radiation from the sun. On Earth its abundance suggests the breakup of CO2 by sunlight was not its only source. Instead, ozone, along with molecular oxygen, O2, also originated from oxygen atoms generated by CO2-eating <a href="http://www.newscientist.com/article/mg16922763.300-bug-breath.html" target="_blank" class="news_link">photosynthetic microbes</a> at least 2.4 billion years ago.




<a href="http://www.newscientist.com/article/dn21021-venus-has-an-ozone-layer-too.html" target="_blank" class="news_link">Continue reading at source: NewScientist.com</a>

Venus has an ozone layer, too