Would the presence of Oxygen in the atmosphere of a planet be an indicator of animal life?

 

Without plants and photosynthesis the Earth's atmosphere would be devoid of Oxygen. Without plants there would be limited scope for animals.

So would this connection be universal?

Depends on the concentration.

Most oxidizers do a pretty good job of sterilizing, don't they ?

Would the presence of Oxygen in the atmosphere of a planet be an indicator of animal life?...

Not necessarily it appears.

Article: >> Dead exoplanets can have oxygen-rich atmospheres too

...Previous research suggested that oxygen could build up on lifeless planets only if they are outside of or on the edge of the habitable zone. But by definition, the best chances for finding aliens are on worlds squarely inside the life-friendly zone, and it was thought that these planets could have oxygen-rich air only if something was alive on the surface to keep pumping it out. Thats because chemical modeling suggested that in the warmer atmospheres of these habitable planets, the highly reactive oxygen molecule would quickly get locked up in other compounds.

 

But taking a closer look at the chemistry, Robin Wordsworth at the University of Chicago found that, even in the middle of the habitable zone, dead worlds made largely of water can have lots of oxygen in their air. Ultraviolet light from the planets star can split molecules of water vapour, with lighter hydrogen drifting into space while oxygen is left behind. The same process could happen on life-free rocky planets if they have low levels of nitrogen or argon, gasses that keep water vapour out of the air and halt oxygen build-up. ...

Not necessarily it appears.

Article: >> Dead exoplanets can have oxygen-rich atmospheres too

Thanks, from the same link.

 

The work suggests that alien-hunters will need to look more carefully at exoplanet signals, such as the exact ratio of oxygen to nitrogen. This makes the task more difficult, says Jack O’Malley-James at the University of St Andrews in the UK. But finding the right mix of chemical clues will increase confidence that we are seeing evidence of life, he says.

Oxygen, on its own doesn't strongly suggest life. Nor does methane.

But having both of them does.

The roughly 1 ppm of methane in the air should react with the oxygen and be destroyed- unless there's something making fresh supplies of it.

 

The same goes for other organic material- like terpenes etc.

 

However, spotting a trace of methane in the air of a planet from a distance would be a challenge.

I'm guessing any combination of elements would be possible. For we will be having a single look at the atmosphere. On the Earth the atmosphere has been altered by life forms e.g. plants producing oxygen, and man putting more carbon dioxide into the atmosphere. These changes take an enormous amount of time to be noticed. So if there were readings taken over a timespan the ratios may be an indicator of something, but it could just be the result of volcanism.

The plane Mercury has oxygen in its atmosphere at a concentration of 42 percent but there is no life there because the atmosphere is so incredibly thin.

Depends on the concentration.

Most oxidizers do a pretty good job of sterilizing, don't they ?

And the thickness of the atmosphere.

The plane Mercury has oxygen in its atmosphere at a concentration of 42 percent but there is no life there because the atmosphere is so incredibly thin.

And the thickness of the atmosphere.

I hadn't noticed that before. Some years ago I studied the possibility that life started on Mercury. I wonder if there is some connection. Where is that oxygen coming from?

This planet was judged being like Earth due to its size and orbital period.

Was it around a similar sized star? Too far away to be useful I'd say.

http://www.msn.com/en-nz/news/world/nasas-kepler-mission-discovers-earths-older-and-bigger-cousin/ar-AAdoesm?ocid=UP97DHP

Edited July 23, 201510 yr by Robittybob1