Thanks to a friend in Grand Rapids, I was linked to a blog hosted by the NY Times called Tierneylab.com.  The writer of the post was sounding off about a pet peeve relating to the use of the term “Organic”.  It seems that there is some confusion as to the use of the adjective organic in relation to certain carbon-containing substances. Tempest in a teapot, you ask? Let the chemistry community decide.

The problem begins to show itself when astronomers and planetary scientists start describing carbon containing materials found in planetary exploration as organic.  Back on earth, the word organic is burdened with both common and scientific usage. So, when descriptions of organic materials found on other worlds begin to arise in discourse, the intent of the usage becomes unclear.

For instance, it could suggest to people that such discovered materials were put in place by some kind of life form. It could suggest to nondiscriminating audiences that the presence of carbon implies life, past, present, or future. Or it might well suggest to higher level audiences that biology-ready raw materials are in place.

The scientists working with the Phoenix Lander have an interesting analytical chore in front of them. Using a robotic platform on Mars, they want to distinguish the presence of organic vs inorganic carbon. What is meant by organic and inorganic is less than clear. But it seems that organic refers to something other than CO2 and carbonate.

In the relatively few journal articles I’ve seen relating to this, the authors are not always precise about the kinds of molecules they are referring to as organic. Irrespective of what is said in the articles, when this work gets to a public forum, the meaning behind the word organic becomes even less clear.   

The TierneyLab post does bring up an interesting question about what is necessary for a substance to be considered organic.  Do graphite, diamond, Buckyball, or soot forms of carbon qualify as organic? What about CO2, CS2, carbonates, CO, HCN, or calcium carbide? Does it make more sense to refer to organic and inorganic carbon, where inorganic carbon is defined as … well, what? 

Seriously, what would it be? CO2? Carbon dioxide is incorporated into glucose by plants and this seems quite organic.  Carbonate? This anion is used to balance our blood pH. Our own metabolic CO2 helps to provide carbonate. This product of metabolism should qualify as organic. CO? Well, Carbon monoxide undergoes Fischer-Tropsch reactions to produce aldehydes. This seems very organic as well. Perhaps the target is a substance with C-H bonds?

There is nothing inherently biological about the C-H bond. The Saturnian moon Titan is blanketed with a thick layer of CH4 (methane) and it seems unlikely that it is of biological origin. Indeed, hydrogen is the most abundant element in the universe and carbon the 4th. That hydrogen and carbon atoms could find each other to form trace methane in a proto solar system isn’t too much of a stretch.

Organic and Inorganic Carbon.  How about we just leave it all as organic? 

Here is what I think. It does matter if a scientist or writer is using language in an imprecise way. If writing or speech implies, for instance, that Mars is rich in life giving organic nutrients when in fact Martian organic matter is really carbonate and CO2, then I believe the language must be altered to reflect that condition. A writer should not leave an impression of past or incipient planetary fecundity when in fact the planet may be an inert ball of metal silicates dusted with a bit of carbonate when the 6 torr CO2 atmosphere kicks up a breeze.