Does Carbon-12 over Carbon 13 equal life on Mars...

Factual Questions
1

The infamous Richard Hoagland is on coattocoast tonight talking about the discovery of CH4 on Mars. He argues that if we find an abudance of Carbon twelve then this indicates that life is probably the source for the Martian methane. On the other hand if we find a higher amount of carbon thirteen then he says that volcanic activity is a better explanation. He said that one of the probes that was lost in recent years had the equipment to ascertain this fact. I have two questions:

  1. Does this observation about c-12 verses c-13 have any relevence for Martian life?

  2. Could we not analyize Martian images taken by Spirit and Opportunity to determine the whether or not C-12 or C-13 was present (using spectrographic analysis). I have read that with atmospheric gasses that we can determine to an extent the nature of even a distant planet’s atomosphere via spectrographic analysis. Could this technique be used with Mars either from ground based observation or from data from previous missions?

2

I guarantee you there is more C12 on Mars than C13, and that difference has nothing whatsoever to do with life. Roughly 1% of carbon atoms in the universe are C13.

3

Additionally, I don’t know if spectrographic methods would suffice to judge the isotope of an element present in a given compound, even if only to ascertain a ratio between two or more isotopes.

4

Most spectroscopic techniques, such as IR or UV, cannot (in most cases) distinguish between isotopes. Mass spectrometry can, and does so very well – in fact, mass spectra of compounds containing atoms that have a large number of naturally occuring isotopes (e.g. molybdenum) have distinctive sets of peaks in the ratio of the natural abundance of these isotopes. Unfortunately, mass spectrometry inherently cannot be done at a distance; it needs an actual sample to be collected and analyzed. Techniques which involve measuring a spectrum of light can be done at great distances away from the light source; for example, you can take IR or UV/VIS spectra of the Sun or even other stars.

5

I assume what this fellow was actually talking about was determining the difference between biogenic methane and thermogenic methane by looking at the degree of fractionation between [sup]12[/sup]C and [sup]13[/sup]C, measured in values per mil (thousandths of a percent). The normal ratio between [sup]12[/sup]C and [sup]13[/sup]C atoms, unaffected by thermal or biological fractionation, would be expressed as 0 per mil. Fractionation does frequently take place, however, as the slight difference in atomic mass can cause one isotope to be favored over the other in processes involving distillation, respiration, etc. As Roches pointed out, fractionation of stable isotopes like [sup]12[/sup]C and [sup]13[/sup]C is determined by a mass spectrometer, for which you need actual samples.

On Earth, methane produced by inorganic thermal reactions is relatively depleted in [sup]13[/sup]C, with del [sup]13[/sup]C values typically in the range of -12 to -40 per mil (less than the standard ratio of [sup]13[/sup]C/[sup]12[/sup]C). Methane produced by methanogens (methane-producing microorganisms) is usually significantly more depleted, with del [sup]13[/sup]C values in the range of -45 to -90 per mil, sometimes as low as -100 per mil. These ranges of values are frequently used here to try to distinguish sources of methane, but problems can arise in trying to assess the relative contributions of thermogenic and biogenic sources of methane if there is potential for significant mixing between the two.

On Mars, the degree of [sup]13[/sup]C fractionation might be an indicator of life, or it might not. Hoagland is making the assumption that Martian methanogens, if present, would behave just as they do on Earth. That isn’t necessarily the case.

Roland, since it appears you are very interested in life beyond this planet, I recommend that you make a trip over to The Astrobiology Web. It will be a lot more reliable than guests on Art Bell’s show or coasttocoast, I promise.

6

and someone like Richard Hoagland. I believe (rightly or wrongly) that conventional, mainstream science often has a tendency to dismiss perspective outside the mainstream even without considering the argument, or “evidence” of the perspective. On the other hand it has been my experience that many who make “paranormal” claims either engage in out right fraud, or actually base their beliefs on flawed, misinterpreted, or just plain bad evidence. I can still remember getting a Biology paper back in highschool (1985) that had NONSENCE written in red ink, due to my position that stomach ulcers were caused by bacteria. Of course mainstream science has now recognized H. Pylori as one of the most widespread etiologies of this disease (and there was support for this position going back to the 1940’s, not definitive support but credible non the less).

7

If Richard Hoagland told me squares have four corners, I’d go find one and count to make sure.

8

I remember reading his first book The Monuments of Mars way back in highschool and being fascinated (but not convinced). On the other hand, I didn’t see any blatent discrepencies in his arguments, just that they didn’t PROVE anything to the level needed for mainstream acceptance.

9

What is it about carbon’s isotope that makes quadruple bonds possible?

10

All isotopes of carbon (C12, 13 and 14) can bond four times. It has nothing to do with being an isotope, which is the result of differences in number of neutrons in the nucleus of the atom, but rather it has to do with the construction of the atom itself.

Carbon has 6 electrons and 6 protons (the number of neutrons are either 6, 7 or 8, add that to the protons, you get the weight of C12, 12 and 14). Because of how atoms are, two of the electrons are located in one “shell” around the nucleus, and the other 4 are located in another shell.

As a general rule, electrons like to be paired up, and atoms are happiest when they have shells with 8 electrons in them, or 4 pairs (the first shell is happiest with only 2, which allows us to have hydrogen and helium as elements). So, in order to haev 8 electrons in its outer shell, carbon must get 4 more, and the way it does this is to share them with other atoms. In the case of CH4, the carbon basically takes the single electron from each hydrogen to make it’s 4 pairs. In return, each hydrogen can be paired with one of the 4 electrons that originally belonged to the carbon.



      H
       *                              *
H*       *H plus             * C *
      *                                *
     H

makes

  H
      **                              
H :  C  : H
      **                               
     H

Carbon can be very happy sharing electrons with many other atoms as well. In the case of life, the most common would be oxygen, nitrogen, phosphorus and sulfur. Each of these have different numbers of electrons to share, and so different combinations can happen, like C=O (where each line is 2 electons) or C-O-X where X is another atom (If you think about it, you’ll see that oxygen therefore has 2 electrons to share, its outter shell has 6 electrons, 4 of which pair with each other, and the other two seek out carbon to share with).

I don’t know if that’s a very clear explanation. To me, this sort of thing is best explained with pictures, not words. Any high school chemistry book, or even just google, can tell you more. Just look up bonding and valence electrons.

Before someone nitpicks me, sometimes atoms don’t share electrons, but rather one will take one from the other: NaCl (table salt) has a sodium atom with one outer shell electron, so it’s happy to give it away to make Na+ and Chlorine has 7, so it will take it from sodium to make 8 total, and Cl -.

11

if Mars has/ or had supported life (actually it probably would still have to have life otherwise the Methane would have probably escaped due the low gravity of Mars). Let’s just settle this thing and get a probe up there with the proper equipment to detect life (if there). After all we DID send such a probe in the Viking landers and they achieved results that might indicate life was present (at the time we didn’t know about Mars’s history of water, and we didn’t have the “meteor” which might contain fossils). As far as I’m concerned this sort of equipement should have been on Opportunity or Spirit.