Scanning for life signs...

[Warped9]

Here a chance for the science whizzes about here to strut their stuff.

In Star Trek as well as other sf we often here the phrase "scanning for life signs" or "detecting life signs." But, really what is it they're scanning for?

I'm not talking about psuedo technbabble that's effectively meaningless, but rather what could realistically be classified as a life sign and how could you go about detecting it, particularly from space.

This subject has become more relevant during the past several years with the detection of several extrasolar planets. There's also the liklihood of developing technology that may be able to detect terrestrial planets as opposed to just Jovian type worlds.

We know that spectroscopic analysis of an atmosphere is entirely possible (from a distance) and that can tell you of the existence of oxygen, carbon dioxide, nitrogen and even ozone, which are indications that life could possibly exist there although not that it is definitely there. From orbit infrared can identify heat sources that might be life. The reflectivity of a planet could be a good indication of water and perhaps even how much.

Is there any way to detect the chemical processes indicative of life?

What other possibilities are there?

 

[Warped9]

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[Pengy]

I like to imagine that enzymes - very large, having moving parts that carry a charge, and often heated above ambient temperature - give off a distinctive thermal signal in the terahertz range that can be tuned for and distinguished from the surroundings. The signals pass through air and some types of inorganic or dead matter, but not through conductive metal or the hull of a starship.

That's still technobabble because I have no idea if it would really work, but at least I haven't reversed the polarity of anything or claimed that some natural phenomenon measures gravity. Maybe someone can think of something more plausible.

 

[anti-matter]

As scanning tech improves I imagine it'll get sensitive enough to register the electro/chemical signals living bodies give off.

Eventually when a large enough data base is realized the device will guesstimate an unknown life sign by the signal it puts out...my 2 cents.

 

[Warped9]

I have a book at home I picked up some years ago called Life Signs that deals with the biology in Star Trek. It discusses many of the ideas put forth in Trek, both reasonable and unlikely and very unlikely. But it is there that I first began reading about what you could realistically look for in a search for life beyond Earth.

The search for and detection of extrasolar planets in the past decade or so has energized the subject into the realm of the credible.

And now that I'm trying my hand at writing original science fiction I want my references to looking for distant worlds and alien life to have at least a ring of credibility and not sound like just more throwaway technobabble.

But when you go looking online for this subject there really doesn't seem to be much out there, possibly because it's something still in its infancy.

 

[Bill Morris]

What you might be looking for, Warped9 is something called Raman spectroscopy. To be useful in identifying minerals, cells, proteins, etc. by merely scanning, what you need is a database that matches return signals with various materials. Such a database has been prepared for the next Mars rover mission, and that rover will carry a Raman spectrometer that is in effect an early tricorder but will be used to identify minerals. If NASA were sending a rover to a planet expected to be teeming with life, then the same kind of device with a database focused on moleclues found in lifeforms should be able to work.

The one going to Mars is only capable of scanning at close range. Using that kind of system to scan from orbit? Maybe, with enough R&D and a much more powerful scanner and receiver, and doing it through atmosphere can't be easy. But for a sci-fi novel, why not?

http://en.wikipedia.org/wiki/Raman_spectroscopy

 

[alchemist]

What you might be looking for, Warped9 is something called Raman spectroscopy. To be useful in identifying minerals, cells, proteins, etc. by merely scanning, what you need is a database that matches return signals with various materials. Such a database has been prepared for the next Mars rover mission, and that rover will carry a Raman spectrometer that is in effect an early tricorder but will be used to identify minerals. If NASA were sending a rover to a planet expected to be teeming with life, then the same kind of device with a database focused on moleclues found in lifeforms should be able to work.

The one going to Mars is only capable of scanning at close range. Using that kind of system to scan from orbit? Maybe, with enough R&D and a much more powerful scanner and receiver, and doing it through atmosphere can't be easy. But for a sci-fi novel, why not?

http://en.wikipedia.org/wiki/Raman_spectroscopy

Having done Raman spectroscopy for 20 years, I don't think the technology will be adaptable easily to either general purpose "life form" scanning or orbital scanning. The Raman effect is very weak and thus requires both the use of a powerful monochromatic source of light (a laser) for molecular stimulation and a very sensitive detection system to measure the changes in the molecular response (called polarizability). Raman spectroscopy is disadvantageous for general work because:

1. Sensitivity is extremely poor because of the weakness of the effect.
2. For "up close" measurements of non-trace chemicals, the laser can burn up the sample if it has the same "color."
3. There are processes that compete with the Raman effect (most notably fluorescence) that often times mask the chemical "fingerprint" signals.

I think ultimately a "life form" scanner is going to involve several electromagnetic wavelengths (e.g., infrared, near-infrared, microwave, radio, etc.) and techniques (e.g., absorption, reflection, resonance, etc.). This is because the myriad types of molecules and atoms defining "life" require different types of probes. And also, a life form scanner is going to need AI software to interpret the results of all the data it acquires. With regards to this point, we're beginning to go down this road now through the use of statistical analysis software routines to interpret spectroscopic chemical data. These routines literally take spectroscopic information and teach themselves what it means (i.e., what fingerprints are linked to what chemicals).

Okay, I'll step away from the podium now. Sorry.

 

[alchemist]

Is there any way to detect the chemical processes indicative of life?

What other possibilities are there?

Okay, one more quick trip to the podium. Putting on both my science and science fiction hats, I think, in addition to looking for the molecular and atomic signatures of life via its interaction with electromagnetic radiation, we also need to be looking for objects that are "organizing." Thus, we need to be scanning for decreases in entropy (i.e., increases in order). The reason for this is that, for example, a dead person and a live person will have the same chemical fingerprints, but the live person will be decreasing its entropy while the dead person will be increasing it.

 

[Bill Morris]

Well, I was just trying to come up with a word Warped9 could use in his fiction. Of course, "sensors" covers more ground, but I think he's looking for something different. Olfactometers that can detect and distinguish various odors exist and are commercially available, but I doubt that's a worthy answer. It doesn't sound good, and they aren't much good if scanning from orbit. But often coming up with a few near misses leads indirectly to an idea that does click.

And any system that has the potential wouldn't have a market that justified billions spent on R&D to get it up to Trek-tech standards any time soon. But eventually, when components. etc. have developed far enough to make it easy, then such advanced things will come about as a matter of course.

 

[Warped9]

Allow me to clarify my intent. I am deficient in thoroughly understanding many things in science (although I generally get the gist of it) and so it would be foolish of me to attempt to go into exhaustive detail in regards to some of the ideas I'm trying to put forth.

That said I hope to use correct terms or references in their proper context to at least suggest something reasonably credible is going on. The story is essentially far future space adventure, but I wish to give it at least a veneer of credibility.

I'll share some bare bones:
- A fast relativistic starship set 900 years in the future exploring a star system 46 light years away (F6V star Tau 1 Eridani).
- Planet landings are via a form of shuttlecraft.
- Various TPF techniques are used enroute to ascertain and confirm whether a terrestrial world is likely there.
- Spectroscopic analysis can reveal the presence of oxygen and other gases associated with life, but not confirmation that life is actually there.
- Analysis of the planet's reflectivity strongly indicates a substantial presence of water.
- In-depth analysis of the planet's atmosphere and physical makeup take place when the ship achieves orbit and can launch aerial probes and what I call "smart sand" which are multitudes of tiny spherical sensors that can be sprayed over a large area to evaluate environmental conditions as well as mineral compositions (is this where Radam spectroscopy could apply?). Smart sand is actually something I read in a newspaper in regards to something I believe the U.S. military was working on in regards to putting sensing devices over a large area prior to troop deployment. I add a small wrinkle in that my "smart sand" eventually degrades after a specified period of time so as not to leave a trace of its existence after its purpose has been served.
- I've read about something called ATP hydrolysis in regards to living organisms producing energy or something to that effect (I have to go back and reread it) and how that might be detected.
- This is a first contact story in that even though humans have explored space within the local region and have found an incredible diversity of life they have still not yet encountered alien intelligence, which of course this story is about.

This isn't meant to be hard sf in the classic sense, but rather space adventure flavored with a reasonable dose of credibility.

The general idea I have is that certain conditions can be studied from afar (whether they be from light years distance or from orbit) but that more detailed analysis still has to be done practically onsite.

 

[alchemist]

Allow me to clarify my intent...

- In-depth analysis of the planet's atmosphere and physical makeup take place when the ship achieves orbit and can launch aerial probes and what I call "smart sand" which are multitudes of tiny spherical sensors that can be sprayed over a large area to evaluate environmental conditions as well as mineral compositions (is this where Radam spectroscopy could apply?). Smart sand is actually something I read in a newspaper in regards to something I believe the U.S. military was working on in regards to putting sensing devices over a large area prior to troop deployment. I add a small wrinkle in that my "smart sand" eventually degrades after a specified period of time so as not to leave a trace of its existence after its purpose has been served.
- I've read about something called ATP hydrolysis in regards to living organisms producing energy or something to that effect (I have to go back and reread it) and how that might be detected.

Thanks for the clarifications.

With regards to your first bullet, Raman spectroscopy could possibly be used in your smart sand because you would be doing the work essentially in situ. It's funny because there is a big push in the scientific community (especially in the health sciences) for the development of a "lab on a chip," that is, for the development of microminiature or nanotechnolgy that could put an analytical laboratory on a microchip.

With regards to your second bullet, ATP hydrolysis is currently detected/measured in the laboratory most commonly using either infrared spectroscopy or magnetic resonance spectroscopy (essentially MRI), both of which measure the structures of molecules. Magnetic resonance spectroscopy has the advantage in that it is less invasive.

 

[Warped9]

So I guess I'm on the right track then.

A friend forwarded me these links which I found helpful and interesting and so I'll share them here.
http://www.newscientist.com/article.ns?id=dn7435
http://ecow.engr.wisc.edu/cgi-bin/g.../microwavesusedtodetectvictimsburiedalive.doc
http://news.nationalgeographic.com/news/2006/07/060711-biosensor.html
http://www.esa.int/esaCP/SEM7QR39ZAD_Life_0.html
http://library.thinkquest.org/C003763/index.php?page=exobio03
http://planetquest.jpl.nasa.gov/TPF/tpf_signsOfLife.cfm
http://www.world-science.net/othernews/070814_dust.htm

 

[The Borg Queen]

I'm not talking about psuedo technbabble that's effectively meaningless, but rather what could realistically be classified as a life sign and how could you go about detecting it, particularly from space.

There isn't anything. All there is, is the psuedo technbabble. It's like asking about how faster-than-light travel could be "realistically" engineered.

 

[Timo]

Oh, I think we're being far too pessimistic here. And far too specific.

Why not go for the obvious - why not search for what life is, what it does? A simple doppler radar would tell you whether anything is moving down there, and it would be easy enough to filter out slow-moving things like glaciers, oscillating things like sea surfaces, or things carried around in a single direction by a simple physical process such as a current. Sure, you might filter out some exotic lifeforms by setting your criteria like that - but if there's life down there, it's likely to exist in considerable diversity, and thus such filtering won't really matter.

Combine your motion scans with a heat scan, as anything that moves under its own power is bound to give off waste heat. You get an idiotproof way of proving that Earth has cows. It doesn't tell you that Earth has earthworms, but you can start working down from the assumption that it has cows - something that would certainly interest your heroic explorers.

With good wide-base interferometry / synthetic aperture trickery and futuristic interpretative software, this should be a breeze from a couple of lightmonths out.

Timo Saloniemi

 

[Warped9]

I'm not talking about psuedo technbabble that's effectively meaningless, but rather what could realistically be classified as a life sign and how could you go about detecting it, particularly from space.

There isn't anything. All there is, is the psuedo technbabble. It's like asking about how faster-than-light travel could be "realistically" engineered.

No, there you're wrong. Today the knowledge and rudimentary science and tech does exist although (not yet) as specific as implied in sf and particularly Trek.

Today we can spectrospically analyze an atmosphere to detect what gases exists there such as oxygen, carbon dioxide, ozone and methane as well as water which are all indications that life could be there, but not that it is definitely there. In the very least we can detect the presence of water and perhaps even vegetation even from a great distance such as light years. But onsite survey is capable of analyzing soil and mineral composition as well as life process signatures such as ATP. And there is advancing tech in regards to using low level microwave frequencies to detect heartbeat and respiration when looking for victims buried in rubble after an earthquake or other disaster. This could be applied to detecting "life signs" within a localized area on the ground.

And if the science can advance sufficiently--and there's yet no definite evidence it can't--then it could be tuned to look for even more specific signatures to tell us what is definitely there.

The major hurdle at present is the means to detect terrestrial sized planets from a distance, and at least the rudiments of that science are already known. Once perfected within perhaps no more than 20-50 years (and quite possibly less) then we will be able to detect potentially life bearing planets from our own solar system. Then it will remain for us to launch either a probe or even more ambitiously a manned expedition to confirm it.

The real crux of this, though, is that we are presently developing the means to detect life as we know it. There is still the question of life existing in such an alien manner that we mightn't even recognize it initially. Presently we can only guess and speculate on life other than what we are familiar with on Earth. If we someday find something truly alien down the road then that will greatly expand our definition of life and give us even more clealry or broadly defined signatures to look for.

 

[The Squire of Gothos]

IIRC, the Russians were going to send a probe to either Mars or Venus, equipped with some sort of device for detecting life forms. I can't remember how it worked or what it looked for, suffice to say that they tried it on Earth's life forms, found it didn't work and junked it to save weight on the journey.

 

[alchemist]

The real crux of this, though, is that we are presently developing the means to detect life as we know it. There is still the question of life existing in such an alien manner that we mightn't even recognize it initially. Presently we can only guess and speculate on life other than what we are familiar with on Earth. If we someday find something truly alien down the road then that will greatly expand our definition of life and give us even more clealry or broadly defined signatures to look for.

This is exactly why I advocate AI as an essential piece to scan for life. As I mentioned previously, we are currently utilizing/developing statistical software algorithms to "learn" from spectroscopic information and form correlations with things we are looking for. All you need to do is feed in the spectroscopic information and then tell the software to correlate it with something (e.g., the sensory quality of peas, the octane rating of gasoline, etc. - two real, working examples, BTW).

 

[Warped9]

This is exactly why I advocate AI as an essential piece to scan for life. As I mentioned previously, we are currently utilizing/developing statistical software algorithms to "learn" from spectroscopic information and form correlations with things we are looking for. All you need to do is feed in the spectroscopic information and then tell the software to correlate it with something (e.g., the sensory quality of peas, the octane rating of gasoline, etc. - two real, working examples, BTW).

Precisely.

It's interesting in that while the TOS writers as well as early sf lit writers were winging it and using just vague enough sounding terminology without really understanding how it could work they also weren't full of shit after all. Their terminology sounded right enough without being too specific such that real science eventually caught up and validated their concept, at least in principle if not in specifics. Cool.

Everything I've read seems to show that I'm on the right track in my general approach and will be able to use more correct terminology rather than meaningless technobabble.