[meteorite-list] sulphurous smell of meteorites (was Temperature of meteorites)

[Piper R.W. Hollier]

Hello Mark and list,

Reports of some meteorites having a sulphurous smell have been of 
interest to me for several years now. My thanks to Mark Grossman for 
the mention of the Sears article (1974) and Ursula Marvin's 
speculations on the subject (2007). I've not seen either reference 
yet and am curious about both.

While reports of sulphurous smells may have subsided, they have not 
by any means ceased entirely. This list had a lively thread on this 
subject back in the fall of 2007 soon after the Carancas fall. I'll 
recount a few salient points of that discussion for those who are new 
to the list.

Visitors to the Carancas crater soon after the impact reported a 
sulfurous odor, and the symptoms of people who reported becoming ill 
at Carancas (irritation of respiratory tract, nausea, vomiting, 
stomach pain, dizziness, headache, skin lesions) are consistent with 
exposure to sulfur dioxide gas and/or to the sulfurous acid (H2SO3) 
that forms when sulfur dioxide dissolves in water (e.g. in the moist 
lining of the lungs and airways). One witness reported that 
meteoritic dust that had been stored in a closed container after 
being collected near the crater gave a sensation that she likened to 
the "stinging of a thousand little bees" when the container was 
opened and the vapors inhaled.

Other relatively recent reports include:

- The Tagish Lake fall in March 2000: "The crumbly, black, porous 
rock fragments have charred, pocked surfaces and retain the smell of 
sulfur." (CNN)

  - The Park Forest, Chicago fall in March 2003: Colby Navarro 
stated,  "Plaster blew all over me and all over the upstairs; then I 
found the rock," then added that it was warm to the touch and smelled 
like the sulfur from fireworks.

It is a well-know fact that sulfur is present in many types of 
meteorites. Ordinary chondrites contain on average 2.1% sulfur, and 
carbonaceous chondrites may contain as much as 6.6%. Sulfur in 
meteorites is normally present entirely as troilite (FeS), but other 
sulfides are found in some meteorites, and carbonaceous chondrites 
contain free sulfur, sulfates, and possibly other sulfur compounds. 
(summarized from B. Mason, "Meteorites", p. 160)

Less well-known is the fact that troilite dissociates at the rather 
low temperature of 427 C (Sterling Webb found this figure somewhere 
during the 2007 discussion). This releases elemental sulfur that can 
in turn combine with atmospheric oxygen to produce sulfur dioxide. 
The distinctive sharp smell that a match gives off when being lit is 
due to the sulfur dioxide formed when sulfur in the matchhead burns.

Thus it should not surprise us all that much that we continue to hear 
reports of freshly-fallen meteorites having a sulfurous smell. It 
would be a natural consequence of heating troilite in air.

Also interesting are reports that sulfurous odors may emanate from 
cut meteorites long after the fall date. From my own experience, I 
can relate that Darryl Pitt showed me a slice of Hvittis (fell in 
Finland, 1901, EL6) at the meteorite fair in Gifhorn, Germany some 
years ago (1999?) and suggested that I sniff it. There was a 
distinctive sulfurous odor, similar to the smell that a match makes 
when you light it -- not especially strong, but nevertheless 
unmistakable. The catalog of the Macovich Meteorite Auction at the 
Tucson mineral show in February 2001 mentions a "smell of sulfur" in 
the description of a Hvittis specimen, possibly the same one that I 
"sampled" in Gifhorn.

There would seem to be good reasons to believe that the laws of 
physics and chemistry, and not just superstitious expectations, are 
behind these "nose-witness" reports.

Best wishes to all,

Piper