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Solfe
2013-Nov-03, 04:46 AM
Are there certain types of geology that simply can't exist without life? Fossil fuels and chalk come to mind as types of geology that shouldn't occur without life, but what other types of geology are impossible without life? Can you have slates and shales without life?

I am not proposing that any planet or moon has life, I simply don't have the basic vocabulary to ask the question the other way around. My google fu has forsaken me.

Colin Robinson
2013-Nov-03, 08:04 AM
Are there certain types of geology that simply can't exist without life? Fossil fuels and chalk come to mind as types of geology that shouldn't occur without life, but what other types of geology are impossible without life? Can you have slates and shales without life?

I am not proposing that any planet or moon has life, I simply don't have the basic vocabulary to ask the question the other way around. My google fu has forsaken me.

Even here on Earth, it can be difficult to determine which geological features were or weren't produced biologically. Take "fossil fuels". The word "fossil" comes from Latin "fossilis" "obtained by digging". Although most scientists think that crude oil (for instance) comes from organisms, a number have argued for a non-biological origin. See the WP page Abiogenic Petroleum Origin (https://en.wikipedia.org/wiki/Abiogenic_petroleum_origin).

Likewise stromatolites there is a statement in the WP article about them (https://en.wikipedia.org/wiki/Stromatolite), backed by a citation from Nature Geoscience, which says:


While features of some stromatolites are suggestive of biological activity, others possess features that are more consistent with abiotic (non-biological) precipitation. Finding reliable ways to distinguish between biologically formed and abiotic stromatolites is an active area of research in geology.

It may be possible one day to use geological features to see whether a particular planet ever had life, but it isn't going to be easy. I think in the case of Mars (for instance) it is more realistic to think of geology as a source of clues about existence or not of past life, rather than as something that can answer the question definitely any time soon.

neilzero
2013-Nov-03, 11:45 AM
The question suggests more related questions. Rock is rare in Florida, except lime rock which is likely fossil coral reef, a colony of sea animals. This is mostly calcium carbonate, but calcium is part of the compound of many kinds of rock. Neil

Solfe
2013-Nov-03, 07:10 PM
Thank you, Neil.

Noclevername
2013-Nov-03, 07:17 PM
Are there certain types of geology that simply can't exist without life?

I'm not certain we can answer that yet. Since Earth has been "contaminated" by ubiquitous life almost since its earliest ages, and we have just barely began to examine small areas of a few other planets and moons, we don't really have a sample size large enough to be sure what can happen geologically in a purely non-biotic environment.

We specifically have no idea what might happen on a lifeless planet with liquid water and an atmosphere to interact with the geology.

Solfe
2013-Nov-04, 12:02 AM
Ok, perhaps this is a better question - are there rocks on Mars or the Moon that simply don't occur here on Earth?

Have there been any cases if slate or shale appearing on Mars or the moon? I've seen pictures of stuff that sort of looks like those two materials, but I'm not a geologist.

Noclevername
2013-Nov-04, 12:35 AM
The Moon:
http://en.wikipedia.org/wiki/KREEP
http://en.wikipedia.org/wiki/Lunar_regolith
http://en.wikipedia.org/wiki/Geology_of_the_Moon#Lunar_rocks

Mars:
http://en.wikipedia.org/wiki/Composition_of_Mars#Mineralogy_and_petrology
http://en.wikipedia.org/wiki/Martian_meteorite
http://en.wikipedia.org/wiki/Martian_soil

To my limited knowledge there have been no specifics on ET findings of either slate or shale, but slate and shale (or analogues) can, I think, hypothetically form without calcite in the absence of life, using largely clay and silica minerals.

Githyanki
2013-Nov-04, 02:40 AM
Isn't limestones from biology.

Noclevername
2013-Nov-04, 02:45 AM
Isn't limestones from biology.

Yes, or from water containing dissolved limestone from other deposits which are also biological in origin.

Solfe
2013-Nov-04, 03:27 AM
Just doing some reading from the links. Florida, or any place that has sink holes, seems more unearthly than any thing on Mars. Cool stuff.

Noclevername
2013-Nov-04, 03:42 AM
Just doing some reading from the links. Florida, or any place that has sink holes, seems more unearthly than any thing on Mars. Cool stuff.

Yeah, my father lives in Florida and had to sell his house because of a sinkhole in his yard. He got 50 cents on the dollar. Still, better to have to leave a house in Florida than a dome on Mars. The air quality is marginally better. ;)

Delvo
2013-Nov-06, 04:24 AM
I don't see how sedimentary rocks could fail to exist, but they'd be different, probably with less visible layering. What's getting deposited in sediments today includes a bunch of organic debris, so without that, only minerals would be getting deposited.

Cosmic Roy
2013-Nov-25, 12:00 AM
This excellent BBC radio programme suggests that life and Earth's geology are tied inextricably.

http://www.bbc.co.uk/programmes/b0368fxd

It seems that not only are many minerals, rock types and even larger formations due to biological action, but the whole process of plate tectonics!

Solfe
2013-Nov-25, 01:15 AM
Thanks! I will take a listen.

Noclevername
2013-Nov-25, 02:26 AM
This excellent BBC radio programme suggests that life and Earth's geology are tied inextricably.

http://www.bbc.co.uk/programmes/b0368fxd

It seems that not only are many minerals, rock types and even larger formations due to biological action, but the whole process of plate tectonics!

An interesting possibility. If it gets any weight of evidence behind it, it could make a useful way to help identify possible life-bearing exoplanets.

The program mentions that part of the theory involves biological origins of clays; does anyone know of possible no-biological sources of clays?

Barabino
2013-Nov-26, 05:08 PM
My mother believes that Moon is rich in diamonds (probably just because moon's silvery color). It seems impossible to me because of lower lava pressure than earth's but i'm no geologist either. Who's right?
Thanx!

Solfe
2013-Nov-26, 07:05 PM
My mother believes that Moon is rich in diamonds (probably just because moon's silvery color). It seems impossible to me because of lower lava pressure than earth's but i'm no geologist either. Who's right?
Thanx!

I don't see why a diamond couldn't be found in a mine on the Moon just like on Earth, but Lunar regolith isn't made of diamonds.

Barabino
2013-Dec-01, 10:31 AM
So, on the moon if I find a volcanic crater i could find diamonds inside their mother rock kymberlite like on earth, but of course the big difference is only that I could not find any handy alluvial deposits.

In the lunar rocks samples, did they find anything like kymberlite?

thanks!