Petrichor

A brief note on the phenomenon by {{ill|Thomas Lambe Phipson|fr|Thomas Phipson}} (1833–1908) appeared in The Chemical News on 17 April 1891[https://upload.wikimedia.org/wikipedia/commons/8/80/The_chemical_news._Volume_63%2C_January_-_June_1891._%28IA_s713id13691660%29.pdf Phipson, T.L., Cause of the Odour Emitted by the Soil of a Garden after a Summer Shower", The Chemical News, Vol.63, No.1638, (17 April 1891, p.179.] and was re-published in its entirety, a month later, in The Scientific American,{{cite journal |title=The Odor of the Soil after a Shower |first1=T.L. |last1=Phipson |journal=Scientific American |volume=64 |number=20 |date=May 16, 1891 |page=308 |jstor=26100386 }} in which he wrote, "This subject, with which I was occupied more than twenty-five years ago, appears from a paragraph in the last number of the Chemical News to have recently attracted the attention of Professor Berthelot and [Monsieur G.] Andre."

Phipson was referring to a short paper read by Berthelot and André at the meeting of the French Académie des Sciences on 23 April 1891, and printed in Volume 112 (1891) of Comptes Rendus, entitled "Sur l'odeur propre de la terre" ("On the earth's own smell").{{cite journal |journal=Comptes rendus de l'Académie des Sciences |title=Sur l'odeur propre de la terre |trans-title=On the earth's own smell |date=January 1891 |volume=1891/01 (Tome 112) |pages=598–599 |url=https://gallica.bnf.fr/ark:/12148/bpt6k3068q/f598.image}}{{cite web |url=https://getpocket.com/explore/item/why-you-can-smell-rain |title=Why You Can Smell Rain |quote=A weather expert explains petrichor – that pleasant, earthy scent that accompanies a storm's first raindrops. |work=The Conversation |date=August 27, 2018 |first1=Tim |last1=Logan |access-date=July 14, 2020}}

Phipson continues, "I find, on referring to my old notes, which are dated 1865, that it is doubtful whether I ever published the results of these observations; and as the distinguished chemists I have just named have not quite solved the problem, I hasten to give the results I obtained so long ago." He then theorizes that the odour "... was due to the presence of organic substances closely related to the essential oils of plants ..." and that these substances consist of "... the fragrance emitted by thousands of flowers ..." absorbed into the pores of the soil, and only released when displaced by rain. After attempts to isolate it, he found that it "... appeared to be very similar to, if not identical with, bromo-cedren derived from essence of cedar."

The phenomenon was first scientifically described in a March 1964 paper by Australian researchers Isabel Bear and Dick Thomas, published in the journal Nature.

{{Cite journal

| volume = 201

| issue = 4923

| pages = 993–995

| first1 = Isabel Joy | last1 = Bear

| first2 = Richard G. | last2 = Thomas

| title = Nature of argillaceous odour

| journal = Nature

| date = March 1964

| doi = 10.1038/201993a0

|bibcode = 1964Natur.201..993B

| s2cid = 4189441

|quote=The diverse nature of the host materials has led us to propose the name 'petrichor' for this apparently unique odour which can be regarded as an 'ichor' or 'tenuous essence' derived from rock or stone […] it does not imply that petrichor is necessarily a fixed chemical entity but rather it denotes an integral odour, variable within a certain easily recognizable osmic latitude.

}}

{{Cite journal

| volume = 33

| issue = 2

| pages = 91

| title = The Smell of Rain

| journal = Weatherwise

| date = 1980

| doi = 10.1080/00431672.1980.9931898

}} Apparently, the printed text is a copy from CSIRO journal Ecos, issue February 1976, p. 32.{{Cite book

|title=The Dord, the Diglot, and an Avocado Or Two: The Hidden Lives and Strange Origins of Words

|first=Anu

|last=Garg

|publisher=Penguin

|year=2007

|isbn=9780452288614

|page=399

|url=https://books.google.com/books?id=SBlK4QrLmiIC&pg=PT399 }}.{{cite journal |journal=The Conversation |title=The smell of rain: how CSIRO invented a new word |date=March 31, 2015 |first1=Howard |last1=Poynton |url=https://theconversation.com/the-smell-of-rain-how-csiro-invented-a-new-word-39231}} Thomas coined the term "petrichor" to refer to what had previously been known as "argillaceous odour".{{cite news|url=https://csiropedia.csiro.au/bear-isabel-joy/|title=Isabel 'Joy' Bear|work=CSIROpedia|publisher=CSIRO|date=11 April 2014|first=Colin|last=Ward|access-date=9 May 2020|quote=Thomas gave the name 'petrichor' to this odour.}} The authors describe how the smell derives from an oil exuded by certain plants during dry periods, whereupon it is absorbed by clay-based soils and rocks. During rain, the oil is released into the air along with another compound, geosmin, a metabolic by-product of certain actinobacteria, such as Streptomyces,{{Cite journal| doi = 10.1038/s41564-020-0697-x| issn = 2058-5276| volume = 5| issue = 6| pages = 821–829| last1 = Becher| first1 = Paul G.| last2 = Verschut| first2 = Vasiliki| last3 = Bibb| first3 = Maureen J.| last4 = Bush| first4 = Matthew J.| last5 = Molnár| first5 = Béla P.| last6 = Barane| first6 = Elisabeth| last7 = Al-Bassam| first7 = Mahmoud M.| last8 = Chandra| first8 = Govind| last9 = Song| first9 = Lijiang| last10 = Challis| first10 = Gregory L.| last11 = Buttner| first11 = Mark J.| last12 = Flärdh| first12 = Klas| title = Developmentally regulated volatiles geosmin and 2-methylisoborneol attract a soil arthropod to Streptomyces bacteria promoting spore dispersal| journal = Nature Microbiology| accessdate = 2022-01-01| date = 2020-06-01| pmid = 32251369| s2cid = 214808046| url = https://www.nature.com/articles/s41564-020-0697-x}} which is emitted by wet soil, producing the distinctive scent; ozone may also be present if there is lightning.{{cite news

|title=Storm Scents: It's True, You Can Smell Oncoming Summer Rain: Researchers have teased out the aromas associated with a rainstorm and deciphered the olfactory messages they convey

|url=https://www.scientificamerican.com/article/storm-scents-smell-rain/

|access-date=July 20, 2012

|work=Scientific American

|date=July 18, 2012

|first=Daisy

|last=Yuhas }} In a follow-up paper, Bear and Thomas (1965) showed that the oil slows seed germination and early plant growth.{{Cite journal

|volume=207

|issue=5005

|pages=1415–1416

|first1=Isabel Joy

|last1=Bear

|first2=Richard G.

|last2=Thomas

|title=Petrichor and plant growth

|journal=Nature

|date=September 1965

|doi=10.1038/2071415a0 |bibcode = 1965Natur.207.1415B |s2cid=4174301

}}

File:Leaf with droplets.jpg

When a raindrop lands on a porous surface, air from the pores forms small bubbles, which float to the surface and release aerosols.{{cite web|last=Chu|first=Jennifer|date=14 January 2015|title=Rainfall can release aerosols, study finds|url=https://newsoffice.mit.edu/2015/rainfall-can-release-aerosols-0114|access-date=17 January 2015|website=MIT News}} Such aerosols carry the scent, as well as bacteria and viruses from the soil. Raindrops that move slower tend to produce more aerosols; this explains why petrichor is more common after light rains. Members of the Actinomycetes, gram-positive bacteria, are responsible for producing these aerosols.

The human nose is sensitive to geosmin and can detect it at concentrations as low as 0.4 parts per billion.{{cite journal | last1 = Polak | first1 = E.H. | last2 = Provasi | first2 = J. | title = Odor sensitivity to geosmin enantiomers | journal = Chemical Senses | volume = 17 | pages = 23–26 | year = 1992 | doi = 10.1093/chemse/17.1.23 }} Some scientists believe that humans may appreciate the rain scent because ancestors relied on rainy weather for survival.{{cite web

|last=Palermo

|first=Elizabeth

|title=Why Does Rain Smell Good?

|publisher=LiveScience.com

|work=Live Science

|date=21 June 2013

|url=http://www.livescience.com/37648-good-smells-rain-petrichor.html

|access-date=17 January 2015 }} Camels in the desert also rely on petrichor to locate sources of water such as oases.{{Cite web |title=Sure can smell the rain |url=https://blogs.egu.eu/divisions/sss/2015/02/24/sure-can-smell-the-rain/ |access-date=2023-08-24 |website=Soil System Sciences |language=en-GB}}

• Dimethyl sulfide – One of the molecules responsible for the odour of the sea
• Mitti attar – a perfume that recreates the loamy smell of a first rain

{{reflist}}

• Bear, I. J. & Thomas, R. G. (September 1966). "Genesis of Petrichor". Geochimica et Cosmochimica Acta. Vol. 30, No. 9. pp. 869–879.

{{wiktionary}}

{{commons category}}

• [http://www.wordsmith.org/words/petrichor.html "Petrichor"] at A Word a Day
• [http://www.oed.com/view/Entry/141889?redirectedFrom=petrichor#eid From the Oxford English Dictionary]
• {{citation |url=https://www.youtube.com/watch?v=lGcE5x8s0B8 |archive-url=https://ghostarchive.org/varchive/youtube/20211212/lGcE5x8s0B8| archive-date=2021-12-12 |url-status=live|title=Where does the smell of rain come from? |type= 3-min YouTube video |first=Joe |last=Hansen |date= 2014-08-18 |access-date= 2018-01-04 |series=It's Okay To Be Smart |publisher=PBS Digital Studios }}{{cbignore}}
• {{citation |url= http://www.straightdope.com/columns/read/3023/what-s-that-smell-right-before-it-rains-plus |title= What's that smell right before it rains? |first= Cecil |last= Adams |author-link= Cecil Adams |date= 2011-11-18 |access-date= 2018-01-04 |website= The Straight Dope |publisher=Sun-Times Media Group }}
• [https://www.metoffice.gov.uk/learning/precipitation/rain/petrichor Petrichor, U.K. Met office.]
• [https://pluviophile.net/petrichor/ Why Is the Smell After It Rains So Appealing? The Petrichor phenomenon]
• [https://www.pluviophile.com/pluviophile/petrichor-why-we-love-the-smell-of-rain Petrichor – Why we Love the Smell of Rain]

Category:1964 neologisms

Category:Rain

Category:Olfaction

Category:Precipitation

Category:Soil