Its surface temperature is hot enough to melt lead, and it rains sulphuric acid, but US scientists think there might yet be life on Venus, floating in its sulphurous clouds.
The existence of life on Venus depends on what the planet was like billions of years ago. The current theory is that when the solar system was young, Venus and Earth were very much alike, and it is possible that there was even surface water on our sister planet.
If the transformation was slow enough, life may have been able to get an initial foothold, according to according to Louis Irwin of the University of Texas at El Paso. He told The BBC"It may well have been Earth-like long enough for life to either emerge or be transported there".
Once established, life on Earth has adapted to almost every available environment. On Earth, bacteria even live and reproduce in the clouds, and Caltech's Professor Andrew Ingersoll thinks that microbes might be able to do the same on Venus.
In a report submitted to the journal of Astrobiology, Professor Ingersoll suggests microbes may be able to eke out a living in the thick clouds that cloak the planet, protected from the sun by sulphur compounds. He is not alone: there is now a proposal with Nasa for a mission to go there and find out.
However, others believe that it was the emergence of life on Earth that stopped our planet undergoing a similar fate. Life on Earth first appeared in the oceans, gradually sucking carbon dioxide from the atmosphere, locking it away in limestone. If the same had happened on Venus, the theory goes, it would have resulted in a similar transformation there.
But Venus is 30 per cent closer to the sun. It is possible that even if life did get started, the oceans boiled away. The clouds would have been the only refuge. "If you think about what life needs in a broad sense then the clouds of Venus might actually be a habitat where something could live," commented David Grinspoon, of the South West Research Institute in Colorado.
He argues that the organisms would, neccesarily, have evolved to take advantage of the conditions, and could have found a way to exploit the abundant UV radiation: "One lifeform's deadly radiation may be another lifeform's lunch".
The mission proposal, now with Nasa, suggests "sending a probe to Venus, not to the surface, but to the clouds". It would be a balloon-like floating craft that would collect samples before launching back into space off from the atmosphere to return to earth. A surface mission would be much more difficult: the atmospheric pressure is 90 times that at sea-level on Earth. ®