Scientists have dashed any remaining hopes of finding life on Venus, the second-closest planet to the Sun.
Clouds on Venus don’t contain enough water to sustain even organisms that are adapted to live in extreme environments on Earth, they reveal.
The researchers, led by Queen’s University Belfast, looked at data from various scientific probes, including Galileo, sent to different planets in the Solar System.
Venus is terrestrial planet similar in size to Earth, but it has a surface temperature around 867°F (464°C) and pressure 92 times that of our home planet.
Today, Venus is a world of intense heat, crushing atmospheric pressure and clouds of corrosive acid.
A high level of sulphuric acid droplets in the planet’s clouds reduce ‘water activity’, the scientists explain.
‘In our study, we looked at the effective concentration of water molecules which we scientifically called water activity,’ author Dr John E Hallsworth at the School of Biological Sciences, Queen’s University Belfast told PA Media.
‘Not only we found the effective concentration of water molecules is slightly below what is needed for the most resilient microorganism on Earth, its more than 100 times too low.
‘It is almost at the bottom of the scale and an unbridgeable distance from what life requires to be active.’
The results appear to contradict research published last year that suggested phosphine gas in Venus’s atmosphere was an indicator of life in the planet’s clouds.
While Venus doesn’t appear to be habitable, researchers found that Jupiter’s clouds have the right water conditions that would allow life as we know it.
‘One thing which we found which was unexpected was that the clouds of Jupiter actually have the right temperature and water activity combination to support active life,’ Dr Hallsworth added.
‘We absolutely hadn’t expected that.
‘I am not suggesting there is life on Jupiter – it would need the right nutrients to be there and I am not sure of that.
‘Life doesn’t only need a nice temperature and water availability to be active. But still, it is a profound and exciting finding and totally unexpected.’
Water activity, measured on a scale of 0 to 1, is equivalent to the relative humidity, or availability of water, in a planet’s atmosphere.
The water activity of an environment can considerably affect organisms, including those that are capable of living in extreme environments, known as extremophiles.
Laboratory studies have shown that life requires a water activity of at least 0.585 for metabolism and reproduction to take place.
The authors found droplets of sulphuric acid reduce the water activity of Venus’ clouds to below 0.004 – more than 100 times less than the limit for life.