NASA’s Curiosity Rover Detects Largest Organic Molecules Found on Mars: decane, undecane, and dodecane

[essentialsaltes]

Scientists probed an existing rock sample inside Curiosity’s Sample Analysis at Mars (SAM) mini-lab and found the molecules decane, undecane, and dodecane. These compounds, which are made up of 10, 11, and 12 carbons, respectively, are thought to be the fragments of fatty acids that were preserved in the sample. Fatty acids are among the organic molecules that on Earth are chemical building blocks of life.

Living things produce fatty acids to help form cell membranes and perform various other functions. But fatty acids also can be made without life, through chemical reactions triggered by various geological processes, including the interaction of water with minerals in hydrothermal vents.

 

[SelfSim]

Testing this out in an Astrobiological Assembly Theory context, (which, admittedly, is far from being mainstreamly accepted), I used Google's AI by asking what is the Assembly Index of Decane. (Assembly index is cited as being a key indicator of life by Astrobiologist Sarah Imari Walker and Lee Cronin, Evolutionary Biochemist).

In assembly theory, the assembly index of decane (a 10-carbon alkane) is 8. Walker and Cronin use 15 as the minimum index for life, but that number is disputed as being unique to life, so my query is nore out of curiosity (I'm just warming to the rover's purpose here .. I think I must also be unintentionally making a pun on the curiosty word here, too ).

So here's AI's more detailed explanation:

• Assembly Index:
  In assembly theory, the assembly index represents the minimal number of steps (or joining operations) needed to build a molecule from its basic building blocks (e.g., monomers).
• Decane's Structure:
  Decane (C10H22) is a straight-chain alkane with 10 carbon atoms. It can be viewed as a chain of 10 methylenes (-CH2-) connected by single bonds.
• Assembly Process:
  To build decane, you can start with a single carbon atom (or a small fragment) and then sequentially add methylenes, effectively "assembling" the chain.
• Calculating the Assembly Index:
  To determine the assembly index, you need to find the shortest path or sequence of steps to build decane. Since decane is a linear chain, you need 9 joining steps to connect the 10 carbon atoms, resulting in an assembly index of 8.

Dodecane is 12 and undecane is 11.

 

[essentialsaltes]

In assembly theory, the assembly index of decane (a 10-carbon alkane) is 8. Walker and Cronin use 15 as the minimum index for life, but that number is disputed as being unique to life, so my query is nore out of curiosity (I'm just warming to the rover's purpose here .. I think I must also be unintentionally making a pun on the curiosty word here, too ).

Dodecane is 12 and undecane is 11.

The NASA folks hypothesize... "these molecules were remnants of the fatty acids undecanoic acid, dodecanoic acid, and tridecanoic acid, respectively." although those are probably not much more complex.

Also...

It’s possible that the Cumberland sample has longer-chain fatty acids, the scientists say, but SAM is not optimized to detect longer chains.

 

[SelfSim]

This is an example for illustrating how this Assembly theory index works:

• Example:
  Building "ABRACADABRA" in assembly theory:
  • Start with "A" (1 step)
  • Add "B" to make "AB" (2 steps)
  • Add "R" to make "ABR" (3 steps)
  • Add "A" to make "ABRA" (4 steps)
  • Add "C" to make "ABRAC" (5 steps)
  • Add "A" to make "ABRACA" (6 steps)
  • Add "D" to make "ABRACAD" (7 steps)
  • Add "A" to make "ABRACADA" (8 steps)
  • Add "B" to make "ABRACADAB" (9 steps)
  • Add "R" to make "ABRACADABRA" (10 steps)
  • The assembly index for "ABRACADABRA" is 10.

So, the idea is to apply this to biggish organic molecules as a way of quantifying the complexity required to build them. Cronin/Walker etal then try to establish the 'copy number' which is used to imply a degree of sophistication in the replication process. This is combined with the quantified Assembly index of the molecule. The net result there, is then used (as empirical evidence) to determine whether or not the molecule was prodcued by life (or not).

 

[SelfSim]

The NASA folks hypothesize... "these molecules were remnants of the fatty acids undecanoic acid, dodecanoic acid, and tridecanoic acid, respectively." although those are probably not much more complex.

Yes .. have they published their paper on how they arrived at that yet?

Also...

It’s possible that the Cumberland sample has longer-chain fatty acids, the scientists say, but SAM is not optimized to detect longer chains.

Yes .. that's sort of their inferred hypothesis/speculation(?) I suppose?

I'm surpised that we're now being told that SAM can't detect longer chains. That's not how SAM was originally pitched to the public, so there must be more to justifying that claim too.

SAM has had a bit of a chequered story since it started exploring the surface. At one stage its wet organic solvent chemical, (MTBSTFA), leaked from its sealed container and contaminated the sample chamber .. (I actually raised this in a one of their public presentations, which caused the presenter a lot of angst .. I felt like I was about to be given the boot, for rudeness, by some burley looking types coming in my direction).

 

[essentialsaltes]

Yes .. have they published their paper on how they arrived at that yet?

" The finding, published Monday in the Proceedings of the National Academy of Sciences, suggests prebiotic chemistry may have advanced further on Mars than previously observed."

Yes .. that's sort of their inferred hypothesis/speculation(?) I suppose?

My first thought was the mass spectrometer didn't have the mass range, but the googles tell me SAM is good up to 535 Dalton, much bigger than dodecane.

 

[AV1611VET]

Looks to me like Mars is telling us two things:

1. Mother Nature cannot produce life.
2. The [strong] Anthropic Principle rules.

 

[SelfSim]

" The finding, published Monday in the Proceedings of the National Academy of Sciences, suggests prebiotic chemistry may have advanced further on Mars than previously observed."

Meh .. paywalled.

My first thought was the mass spectrometer didn't have the mass range, but the googles tell me SAM is good up to 535 Dalton, much bigger than dodecane.

Yeah ..

This is yet another example which demonstrates the futility of going out and seeking individual classes of known bio-organic molecules from Earth's biosphere. Even if one finds big ones, I still don't think the result will really mean much even its its a perfect match with our own .. at least from mass spectrometer view of chemistry(?) A theoretical context is needed to interpret any organic chemistry detected by mass spectrometers.
This is what Walker/Cronin are on about .. there needs to be a theory of life which is able to be remotely testable .. and Astrobiologists still haven't really come up with one (maybe except for the Walker/Cronin attempt, which may be inadequate also) .. The Walker/Cronin method is better than NASA's none though, I guess .. It all comes down to what is our testable definition of what we mean by 'life' .. (and we still don't actually know the answer from a practical, useful purpose perspective).

 

[Hans Blaster]

Scientists probed an existing rock sample inside Curiosity’s Sample Analysis at Mars (SAM) mini-lab and found the molecules decane, undecane, and dodecane. These compounds, which are made up of 10, 11, and 12 carbons, respectively, are thought to be the fragments of fatty acids that were preserved in the sample. Fatty acids are among the organic molecules that on Earth are chemical building blocks of life.

Living things produce fatty acids to help form cell membranes and perform various other functions. But fatty acids also can be made without life, through chemical reactions triggered by various geological processes, including the interaction of water with minerals in hydrothermal vents.

I thought that was how you counted from 10 to 12 in Martian:

decane,
undecane,
dodecane,

Clearly a romance language like italian: dieci, undici, dodici,...

 

[SelfSim]

I thought that was how you counted from 10 to 12 in Martian:

decane,
undecane,
dodecane,

Clearly a romance language like italian: dieci, undici, dodici,...

(Ahh .. I dunno .. these Physicists are just so not understanding of how hard it is for Astrobiologists .. there just ain't no respect .. )



PS: Mind you, George Gaylord Simpson famously questioned the validity of exobiology, stating in 1964 that "this 'science' has yet to demonstrate that its subject matter exists"!

 

[awstar]

Scientists probed an existing rock sample inside Curiosity’s Sample Analysis at Mars (SAM) mini-lab and found the molecules decane, undecane, and dodecane. These compounds, which are made up of 10, 11, and 12 carbons, respectively, are thought to be the fragments of fatty acids that were preserved in the sample. Fatty acids are among the organic molecules that on Earth are chemical building blocks of life.

I'm not trying to start an argument, or continue one. Just presenting three facts for your consideration:

Fact 1:

my question:

where are the molecules decane, undecane, and dodecane found in nature?


ChatGPT said:

Decane, undecane, and dodecane are straight-chain alkanes (hydrocarbons) commonly found in natural sources, particularly in petroleum and biological systems. Here’s where they occur in nature:

1. Crude Oil and Natural Gas – These alkanes are present in varying amounts in crude oil and natural gas, from which they are extracted and refined for use as fuels, solvents, and chemical feedstocks.
2. Plant Waxes – These hydrocarbons are components of plant cuticle waxes, helping to reduce water loss and protect against environmental stress.
3. Essential Oils – Some plants produce small amounts of these alkanes in their essential oils. For example, certain flowers and fruits emit volatile hydrocarbons that contribute to their aroma.
4. Marine Organisms – Some marine bacteria and algae produce hydrocarbons, including medium-chain alkanes like decane, undecane, and dodecane, as part of their metabolic processes.
5. Insects – Some insects, such as ants and bees, use alkanes as part of their cuticular wax to prevent water loss and for chemical communication.

=================================================

1. FACT 2: Walt Brown made a prediction many years ago

PREDICTION 38: Bacteria will be found on Mars. Their DNA will be similar to Earth’s bacteria. Furthermore, isotopes of the carbon in Mars’ methane will show the methane’s origin is biological.

==================================================

FACT 3:

my question:

do any of the three (molecules decane, undecane, and dodecane) have any isotopes of the carbon in them?

ChatGPT said:

Yes! In nature, decane, undecane, and dodecane can contain carbon isotopes, primarily due to the natural distribution of carbon isotopes in the environment. The key isotopes of carbon that may be present in these molecules are:

1. Carbon-12
   – This is the most abundant isotope (~98.9%) and forms the backbone of most organic molecules.
2. Carbon-13 – A stable isotope that makes up about 1.1% of natural carbon. Some fraction of the carbon atoms in decane, undecane, and dodecane molecules will be 13C depending on their source.
3. Carbon-14 – A radioactive isotope with a very small natural abundance. It is mostly found in biological materials due to atmospheric carbon cycling but decays over time (half-life ~5,730 years). Petroleum-derived hydrocarbons have very little 14C because they come from ancient organic matter where all the 14C has decayed.

 

[Warden_of_the_Storm]

I'm not trying to start an argument, or continue one. Just presenting three facts for your consideration:

I see a fact, a claim and a fact.

 

[essentialsaltes]

I'm not trying to start an argument, or continue one. Just presenting three facts for your consideration:

A little chatGPT is a dangerous thing.

"Furthermore, isotopes of the carbon in Mars’ methane will show the methane’s origin is biological."

I think the idea is that (in analogy with earth) living things on Mars that are 'breathing' carbon dioxide from the atmosphere and excreting methane would produce methane with more carbon-14 isotope than expected, and this would signal the biological origin.

But your Fact #3 is far removed from any relevance to this point (apart from explaining why carbon-14 is important). The AI is clearly answering about terrestrial molecules, not these Martian ones. And these Martian molecules are not methane but much bigger hydrocarbons -- not a deal breaker exactly, but not what Brown was getting at. But the fact that they're buried inside rocks would seem to demonstrate that no living thing in there breathed anything any time recently. So any putative carbon-14 signal would long ago have decayed away.

But it's worth checking, and I expect the mass spec would be sensitive enough to note that some of the decane was a couple amu heavy, indicating an unusual isotope was present.

 

[SelfSim]

Already done (on earlier sediment samples).. results were inconclusive.

Depleted carbon isotope compositions observed at Gale crater, Mars. PNAs, Jan 2022.

Abstract.
Obtaining carbon isotopic information for organic carbon from Martian sediments has long been a goal of planetary science, as it has the potential to elucidate the origin of such carbon and aspects of Martian carbon cycling. Carbon isotopic values (δ13CVPDB) of the methane released during pyrolysis of 24 powder samples at Gale crater, Mars, show a high degree of variation (−137 ± 8‰ to +22 ± 10‰) when measured by the tunable laser spectrometer portion of the Sample Analysis at Mars instrument suite during evolved gas analysis. Included in these data are 10 measured δ13C values less than −70‰ found for six different sampling locations, all potentially associated with a possible paleosurface. There are multiple plausible explanations for the anomalously depleted 13C observed in evolved methane, but no single explanation can be accepted without further research. Three possible explanations are the photolysis of biological methane released from the subsurface, photoreduction of atmospheric CO2, and deposition of cosmic dust during passage through a galactic molecular cloud. All three of these scenarios are unconventional, unlike processes common on Earth.

 

[sjastro]

If scientists are looking for decane, undecane, and dodecane on Mars, are dentists looking for novacane (sic).

I posed the question to GPT-4.

​

We are doomed AI understands an appalling Dad joke and responds in kind.

 

[AV1611VET]

If scientists are looking for decane, undecane, and dodecane on Mars, are dentists looking for novacane (sic).

No.

Dentists don't use Novocaine anymore.

 

[SelfSim]

If scientists are looking for decane, undecane, and dodecane on Mars, are dentists looking for novacane (sic).

I posed the question to GPT-4.

View attachment 362803
​

We are doomed AI understands an appalling Dad joke and responds in kind.

Sigh .. ... ah dunno .. just aint no respect for pre-biotic focused Astrobiologists .. yet again!

It shoulda sent you off to calculate the assembly index of novacaine, or reciting the sequence of aminos in tintin .. as punishment for such disrespect!?

(Mind you, I think its joke might well be an even more severe punishment?)