PDA

View Full Version here: : Do we Understand Water?


CraigS
12-02-2011, 10:46 AM
Here's another one .. just to keep me honest about water's impacts on 'Habitability' and the prospects of life, here's some more interesting evidence in support of biological evolution seeming to be dependent, at a quantum level, on an unpredicted behaviour of water …

Physicists discover new quantum state of water (http://physicsworld.com/cws/article/news/45037)



Well .. maybe … but the interesting thing for me, is that we're still grappling to understand the molecule which (arguably) dominates the planet and us …



Interesting article.

Cheers

renormalised
12-02-2011, 01:40 PM
There's a lot we still don't know about the properties of water.

adman
12-02-2011, 01:57 PM
did you know that it is a polar molecule which is why MRI scans work?

renormalised
12-02-2011, 02:16 PM
Yes:):)

CraigS
12-02-2011, 02:33 PM
How they detect water remotely on exoplanets is changing, also.

One method used (in 2008), for HD 189733b used emitted infrared light, as opposed to light absorbed from the parent star. They had to look at about 10 revolutions of the planet, comparing the light when it was in front of the star, to when it was behind it and subtracting the two figures to get the emitted light .. One revolution wasn't enough to confirm the 6.2 micron vibrational mode (expected in a hot giant) .. it took 10 observations to confirm it.

There was quite a lot of controversy about the original detection .. ie: it was disputed until they finally resolved it all, using the method above.

Interesting.

Cheers

CraigS
12-02-2011, 02:42 PM
Here's another one (not sure if this one's solved yet, either) ..

Apparently, in the near infrared spectrum, the refractive index of water can be affected by a strong magnetic field. They reckon the field somehow strengthens the hydrogen bonds but the exact mechanism was a mystery (in 2004).

Because water is diamagnetic, it shouldn't be effected by the field. They suspected a Lorentz force may have been responsible for strengthening the bonds .. which also results in an increase in the melting point.

Interesting again..

Cheers

marki
12-02-2011, 06:57 PM
Yes water is a very interesting molecule. Its properties seem to depend very much on the environment it finds itself. If you put it in a pressure vessel and get it super heated above 250 degree C whilst still in the liquid phase it is able to be used as a solvent for some organic compounds negating the need for harsher chemicals. When cooled the organic and water seperate into layers and its easy to retrieve the products. As temperature shifts so does the value of Kw which inturn moves the pH value of the neutral point. And then there is several different forms of the clathrate structure (7 from memory) when in the solid phase again depending on environment. Me thinks we have a lot to learn about good old water and I reckon we are in for a few suprises.

Mark

Barrykgerdes
12-02-2011, 09:10 PM
How about water as a cutting tool. High pressure/high speed jet cuts steel like a knife.

Heat water in an enclosed vessel till it reaches its critical temperature where it can't exist as a fluid. What an explosion!

Barry

CraigS
13-02-2011, 11:12 AM
Interesting stuff there guys …

Along the same lines as Mark's post, there's also the 'Superionic State' of water. It was only theoretical in 2005(ish) but now, they've created it in the lab.

The interesting thing about this, is that it exists between solid and liquid states at extreme pressures & temperatures (eg: Neptune and Uranus). It also glows yellow.

A neat couple of videos here (https://www.llnl.gov/news/newsreleases/2005/SF-05-04-01.html) (and an accompanying article).



One point to make about all this, is that the remote spectroscopic detection of water may, or may not have implications on habitability.

There's other things to take into consideration before assuming its in a state where life can make use of it. Let's face it, even if it is in a liquid state, there's probably other compounds dissolved in it, which could easily make it not conducive to life.

Would such an environment be presently classified as 'habitable' ?

Cheers

renormalised
13-02-2011, 04:32 PM
Depends on what you define as being "life". Remember, carbon can make an enormous range of organic molecules, many of which we most likely haven't even found yet. There could be organic molecules in living systems on other planets that are so robust that they can survive in conditions which might completely destroy our forms of organics. What about life on carbon rich planets. The medium for dissolving organics there would be petroleum, not water. What about life on those planets. Just because a planet looks harsh by our own standards doesn't mean it can't support life, or isn't supporting life presently. Even on planets like our own, just because the water has other compounds dissolved in it doesn't make it inhospitable. Looks at the black smokers along deep ocean ridges. The pressures and conditions there would kill us stone dead in an instant, yet life flourishes in these environments...and it's fundamentally the same as we are, physically and biochemically.

I think we have to be very careful about being a little bit too narrow minded about our definitions of habitability and life in general. We can miss out on seeing the life present in an environment where we deem it unsuitable, just because our scientific paradigm at the time says that to be the case.

avandonk
13-02-2011, 04:58 PM
You only have to check out the extremophiles. Single celled bacteria that can live at high temperatures. Their enzymes are very robust not to mention the way they package their DNA and RNA.

Your whole physiology depends on DNA, RNA and proteins all interacting in an aqueous environment. You would not exist without Hydrogen bonds.
Without Hydrogen bonds organic life would not exist.

It gets even better as all organic macromolecules have a 'shell' of water bound by Hydrogen bonds. I have seen ordered water 'shells' in high resolution xray structures.

Check out this substance called trehalose it mimics water and can protect living organisms from dessication and or freezing.

Bert

renormalised
13-02-2011, 05:01 PM
Any water detected spectroscopically is going to be either normal liquid or water vapour (either under normal or superheated conditions). You can't detect superionic water spectroscopically because it can only occur in the interiors of ice giants. Even high pressure, med temp ices such as Ice VIII and IX can't be detected spectroscopically because they occur in the interiors of water worlds or at the bottom of oceans on large super earths. They can only be inferred by experimentation based on theory, or if you have robust enough probes, sampled directly.

marki
13-02-2011, 06:38 PM
Interesting enough Bert they are currently redefining our understandings of the hydrogen bond from a strongish dipole-dipole attraction. Current research has shown a far greater interaction between valence electrons then first thought with some evidence of electrons jumping between molecules. The IUPAC mob are considering taking it out of Vander Waals (used very loosely here) and giving a status all of its own. We have so much to learn even about the things we think we know.

Mark

avandonk
13-02-2011, 08:54 PM
Do you not think Mark that evolution has not figured out the quantum interactions that are possible for even macromolecules?

bert

marki
13-02-2011, 10:36 PM
Bert I have always been in awe of the greatest chemists on Earth....Prokaryotic cells.

Mark

Brian W
13-02-2011, 10:58 PM
All I know is that water in any amount and in any state destroys single malt!:innocent:

CraigS
14-02-2011, 09:07 AM
Interesting perspectives here folks - thank you all. Got me thinking (heaps).

Don’t get me wrong here, I’m comfortable with the standard ‘pillars’ of physics, biology, etc, but I’m also addicted to exploring possibilities that exist in between, especially in speculative conversations and topics. The ‘possibilities of exo-life’ topic is always speculative. I’m comfortable with both optimistic and pessimistic perspectives - both are equally valid, until exo-life is discovered, and the only way we’ll ever do that, is by going and looking for it.

That being said, I guess I’m left wondering about all of the factors that need to be considered following the confirmation of an exo-planet classified as being within the ‘Habitable Zone’.

From our earthly experience, liquid water would be crucial in order for life, (as we know it), to exist. (Life as we don’t know it, could also exist, but I don’t know how we’d recognise it).

So, I’m then left wondering what can be said about exo-environments possessing liquid water, but not exhibiting life.

I can envisage such environments, but I’m just pondering how can we ever conceive of the possibility of the frequency of occurrence of these, given our own earthly perspectives ? Can we get a perspective on how limiting (or otherwise), our earthly views may be, in the hunt for life within our observable universe ?
(Just a mind exercise - I’m not pushing any particular agenda .. just pondering the effects our thinking limits may impose on the resultant view).

For example. ‘Evolution’ is always accompanied by ‘Natural Selection’. Is there an environment we can think of where Natural Selection could actually extinguish the progress of evolution towards abundant life ? (It would have to be cyclical .. ). How precarious is the balance ? (Remember the ‘butterfly effect’). How much do we know about the dependencies which may result in unsuccessful life ? Are we considering these aspects in our optimistic views on exo-life ? If so, what are the dependencies ? (I’m not sure I’ve ever thought about them .. so I have no idea of what they might be).

Just a thought exercise based on what we know about Physics, Biology and water .. and yes .. it is purely speculative, (so no -one has to be right .. and no-one has to be wrong. ;) :)

Cheers & Rgds.

renormalised
14-02-2011, 09:48 AM
The only real way we're ever going to know about any planet being habitable or inhabited is to actually go there. All our best instruments will ever do is just give us an indication of possible habitability, unless we receive an FM or AM signal from a planet, then it's a foregone conclusion. However, that also depends on their level of technology. But, no intelligent technologies there and it will only be an indication based on what we know about planetary ecosystems and non biological processes.

CraigS
14-02-2011, 11:06 AM
Hi Carl;

Yep agreed ... its a subtle point and interestingly, the Mars Express OMEGA instrument was an orbital spectrometer, which worked by analysing the reflected absorption spectra (in the near infrared range). They pointed it at the ice in the southern polar region of Mars in 2004 (ish), to infer the proportions of water ice to frozen CO2. I guess the raw measurement was still measuring the absorption of CO2 and H2O in the gaseous states, but the end conclusion talked about the proportions of solid states, of both compounds.

From the results of this, I think there are shades of grey when it comes to the Habitability/Possibility of life discussion and the presence, (via remote detection), of water. Here is an example of where proportions of frozen water/CO2 have been inferred, based on remotely measured spectroscopic (and visual/optical) data. Whilst there may be water, no inference can be made about the presence/absence of life, because of the presence of (surface) water. Clearly, the environment renders it constantly in either the solid or the gaseous state. (Which was the point I was raising in my post #9 .. sorry if it wasn’t expressed as clearly as possible).

(You also covered this aspect in your above response).

:)

Cheers

CraigS
14-02-2011, 02:07 PM
So on that note, the next Mars rover, 'Curiosity' will be launched in Nov 2011.

It will have an extensive payload of sensory equipment, the main one for detecting possible life will be SAM (Sample Analysis at Mars). It will have a Quadrupole MAss Spectrometer (QMS), a Gas Chromotograph (GC) and a Tunable Laser Spectrometer (TLS).

The TLS will be used to look for Methane which is a key biomarker. But methane can be produced by non-biological means, so when it is detected in the atmosphere of a planet, biology may not necessarily involved. The differentiator they've worked out is to look for the pecentage of Carbon 12 in the methane. The higher the percentage of C-12, the more likely the methane it is from a biological source.

Prokaryote by-products, specifically methane, is exactly what the TLS is engineered to look for.

But even here on Earth, it seems that Prokaryote methane falls outside the accepted range of biogenic methane, and I don't think they've quite figured out exactly why, just yet (?). They still have to consider the environment in which the C-12 measurements are taken, in order to talk about the probability that the origins are from biological sources.

Interesting article about it all is here (http://www.astrobio.net/exclusive/2765/making-sense-of-mars-methane).

Even local detection of life (ie: at the site itself), seems to be a challenge for us at the moment ! Not particularly straight-forward.

Interesting …

Is remote isotopic detection of C-12 in Methane atmospheres possible ? :question:

Cheers

AussieSky
14-02-2011, 07:18 PM
Water? Hah! Dont talk to me about water... When *I* were a lad, we had to bash our own Hydrogen and Oxygen molecules together......

*GHF*

avandonk
15-02-2011, 01:04 PM
Without their past blind random experiments in chemistry for about three billion years leading to self organization, mettalloenzymes etc and their still current existence we would not survive let alone exist!

By the way 30% of your dry weight is foreign bacteria etc that allow you to function. So where do "you" start and end? "You" are inextricably linked to every interaction back to the dawn of time. "You" are just a tiny knot or node on the vast tapestry of existence.
The fact that we can contemplate it, is a bonus!

Our chemical industries rely on temperatures and pressures and solvents that are not attainable by life.

When we get as smart as the Prokaryotic cells we may stop polluting and destroying SpaceShip Earth.

Bert

marki
16-02-2011, 11:08 PM
Agree totally Bert. I was always facinated by mitochondria and the idea that in the distance past they built a symbiotic relationship with other cells to produce eukaryotic cells. The ability to self replicate whilst retaining their coding integrity and cytochrome a + a3 with its copper ion core at the end of the electron transport chain were of particular interest. The change in 3D structure as well as shifts in the sigma and pi bonds needed to oxidise oxygen used to get the old brain ticking for sure and I used to spend hours drawing molecular orbital diagrams trying to work out what was happening. That it all took place in a fluid and dynamic environment was also food for thought. But to stay with the threads original intention the biochemists used to make us calculate the number of free protons inside the mitochondria based on pH. I always used to get 8 but had lots of trouble imagining the device they used to determine the pH :P.

Mark