search for life

[krompir2]

''We are in year 2212 and chinese space probe approches to solar system Gliese 87. Objective is to find possible trays of life, including the most simple life forms. How do you think the space probe is equipt in order to find life? What kind of substances should it search for? Where on planet is a smart place to start search?''

 

This is the question my college biochemistry profesor asked us to think about it at the last lecture. It is actually a very decent question and I would like to hear an opinion from a more sophisticated mind.

[Moontanman]

''We are in year 2212 and chinese space probe approches to solar system Gliese 87. Objective is to find possible trays of life, including the most simple life forms. How do you think the space probe is equipt in order to find life? What kind of substances should it search for? Where on planet is a smart place to start search?''

 

This is the question my college biochemistry profesor asked us to think about it at the last lecture. It is actually a very decent question and I would like to hear an opinion from a more sophisticated mind.

 

 

They would search for a planet with an oxygen atmosphere that contains methane...

[krompir2]

sounds about right. But oxgen and methane it self isnt proof of anything. How do they analyze soil for example? What instrument such space probe, when it lands, should have?

[Moontanman]

sounds about right. But oxgen and methane it self isnt proof of anything. How do they analyze soil for example? What instrument such space probe, when it lands, should have?

 

 

Actually oxygen and methane is proof of something. An extensive oxygen atmosphere is unstable and can come about only with a mechanism to keep producing oxygen, life is the only way known that oxygen can be a large part of an atmosphere. methane is also unstable in an oxygen atmosphere. in both cases biology produces the oxygen and produces the methane.

 

Unless there is life, you cannot have the two together. Actually just a large percentage of oxygen is indicative of life.

[Jens]

Actually just a large percentage of oxygen is indicative of life.

I fully agree. O₂ is a very reactive molecule that in contrast to N₂ can only be maitained at a high level in the athmosphere, if there is a source producing it (and this source is not the hot vulcanos, it can only be life -- to our current knowledge)

 

Just some further explanations:

Even though on earth bacteria and archaea have evolved plenty other ways to live from inorganic compounds there is a good reason why on another planet life might also produce O₂. If on this other planet like on earth the main carbon source is CO₂, this means life forms must oxidize another inorganic substance to reduce CO₂. The best way to get independent of this scare other substances (e.g. H₂S) is to oxidize water, which is everywhere (since we assume life will only evlolve with water anyhow.). Oxidizing water means producing O₂ out of water. This capability evolved on earth only late compared to other pathways (since it is rather tricky to do), but obviously it is a kind of natural optimum. So it is fair to assume that this can happen on another planet with a realistic probability, if there is is life on this planet already present.

 

How do they analyze soil for example? What instrument such space probe, when it lands, should have?

 

Since this extraterrestrial life does not necessarily have DNA, RNA or proteins (but equivalent macromolecules) and since already terrestrial life has a huge chemical variability on what it does to its environment, my quick answer is as follows:

- make a photo/film to search for macroscopic life

- make microscopic pictures of water and humid soil

...send the photos/films back to earth.

(of course try it out in plenty different environments on earth first).

 

On a chemical level life is probably easier to identify by its components than by its reactions with the environment (with the exception of oxygen production). So a very sensitive test looking for organic macromolecules in water-rich places (were they should not occur chemically) is also a direction to go.

 

...but others might have better ideas.....

Edited October 21, 2012 by Jens

[dmaiski]

best way to look for life would be to search for highly chemically active sources, in other words probe for metabolism, how you would do this? I don’t know

 

for macroscopic intelligent life, the easiest way to probe for it is to look for the roads, "god doesn’t build in straight lines"

 

for macroscopic life in general, optical analysis of the planets surface, look for anything that moves

 

for microscopic life look for traces of carbon chemistry NMR should work well for this, and in 2212 we will have enough processor power to NMR a whole cell

 

for exotic life(ie. non carbon based) use full EM spectrum sweeps of the area and search for anomalous areas, then investigate, take samples, and analyse them through every technique you can cram into the probe