Launched in late 2005, the European Space Agency's Venus Express has been circling the neighoring planet since April 2006. Image credit/ESA
The European Space Agency’s Venus Express spacecraft has detected a high altitude ozone layer surrounding the bright planet, a characteristic it shares with the Earth and Mars.
The finding, reported by ESA, earlier this month, could help scientists determine the prospect for life on other planets.
Ozone’s presence is important to life on Earth because molecules of the gas — comprised of three rather than two oxygen atoms — absorb much of the sun’s harmful ultraviolet radiation, thus serving as a protective shield to biological activity on the surface. Sun-like stars are plentiful.
The ultimate source of ozone may well be early biological activity.
On Earth, the build up of oxygen and ozone began about 2.4 billion years ago — or about two billion years after the sun and planets formed.
Simple life forms called microbes may have excreted oxygen as a waste gas, much as plant life around the Earth does now. Together, these life forms serve to replenish the Earth’s oxygen and ozone.
As a consequence, some astrobiologists — scientists who study the possibility of extraterrestrial life — have suggested that the presence of carbon dioxide, oxygen and ozone in a planet’s atmosphere may be a tell tale sign of biological activity.
These critical gases could be detected with powerful space telescopes equipped with instruments properly tuned to detect their signatures.
The Venus Express findings reported by ESA suggest the levels of ozone detected will be crucial to making an accurate determination of whether biological activity was the source.
Mars has ozone as well but in such a small amount that the source is likely the breakup of carbon dioxide in the thin atmosphere by sunlight and a recombining of the CO2 into ozone and other molecules.
The findings from ESA’s Venus Express support a similar situation on Venus: a small ozone build-up at high altitude by non-biological means.
The Earth’s ozone layer is spread across a much lower altitude — 15 miles up or so — and is 100 to 1,000 times denser than the ozone layer on Venus, according to comparisons made by the Venus Express science team.
The findings seem to support theoretical astrobiology modeling that suggests ozone concentrations must be at least 20 percent those of the Earth before life — as we know it — could be the source, according to European experts.