Signs of Microbial Life on Venus?

All eyes are now on planet Venus, our bright morning and evening star.

In the 1950s Venus was one of the most dreamed of and speculated about planets in the solar system. Science fiction portrayed it as a swampy planet covered in rain forests and abundant with strange alien life. Then, after the Soviet Venera missions discovered the hellish conditions on the surface, interest waned somewhat and attention shifted to Mars.

With recent discoveries of Phosphine gas in the planet’s atmosphere, Venus looks set to recapture all of its human wonder and fascination.

Venus has always had the potential to harbour life high in its atmosphere. While its surface is baking hot with crushing pressures, its upper atmosphere is a relatively warm and clement environment.

So far we can’t imagine a natural process which could produce such high concentrations of phosphine gas in the Venus atmosphere but that doesn’t mean there isn’t an explanation that precludes life. Meanwhile we are left to speculate about the many possibilities, including the most tantalising of all, that some form of ancient anaerobic microbial life exists, or has existed, within Venus’s upper atmosphere.

‘Not too hot and not too cold’

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The Goldilocks zone around three different type of stars

The Goldilocks Zone.  The above image is a great illustration of the relative size of the habitable zone around different types of star, with stars like our Sun at the bottom.

Even very dim M class dwarf stars (pictured top) could harbour planets with liquid water – the planets would just need to be situated much closer in. These stars can have very active magnetic fields however, frequently throwing harmful radiation out towards any orbiting planets.  M class stars are also extremely stable, some destined to burn for over 100 billions years, much longer than our Sun which has around 4 billion years of fuel left.

In the middle we see the K class dwarf stars. These will also out live our Sun (by a factor of 4), have nice wide zones of habitation, and much less magnetic activity than the M class stars.  Potentially these K class stars are the ideal incubators for the slow evolution of life, and there’s plenty of them. Nearly 13% of stars in our galaxy are K class red dwarfs.  That’s approximately 26 billion in our galaxy alone! 

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An artist’s impression of a rocky world orbiting a red dwarf star, like the M and K class stars mentioned above.