View source for Biology:Murchison meteorite

{{Short description|meteorite of notable scientific interest}}
{{Infobox meteorite
| Name                      = Murchison meteorite
| Image                     = Murchison crop.jpg
| Image_caption             = A Murchison meteorite specimen at the National Museum of Natural History, Washington, D.C.
| Type                      = [[Astronomy:Chondrite|Chondrite]]
| Class                     = Carbonaceous chondrite
| Group                     = CM2
| Structural_classification =
| Composition               = 22.13% total [[Chemistry:Iron|iron]], 12% [[Astronomy:Asteroidal water|water]]
| Shock                     = S1–2
| Weathering                =
| Country                   = Australia
| Region                    = Victoria
| Lat_Long                  = {{coord|36|37|S|145|12|E|display=inline,title}}<ref name="database">{{metbull|16875|Murchison}}</ref>
| Observed_fall             = Yes
| Fall_date                 = 28 September 1969
| TKW                       = {{cvt|100|kg||}}
| Image2                    = Murchison-meteorite-stardust.jpg
| Image2_caption            = Pair of grains from the Murchison meteorite
}}

The '''Murchison meteorite''' is a [[Astronomy:Meteorite|meteorite]] that fell in Australia in 1969 near Murchison, Victoria. It belongs to a group of meteorites rich in [[Chemistry:Organic compound|organic compound]]s. Due to its mass (over {{cvt|100|kg|||abbr=|order=|disp=or}}) and the fact that it was an [[Astronomy:Meteorite fall|observed fall]], the Murchison meteorite is one of the most studied of all [[Astronomy:Meteorite|meteorite]]s.<ref name="Botta">{{cite journal |last1=Botta |first1=Oliver |last2=Bada |first2=Jeffrey L. |title=Extraterrestrial Organic Compounds in Meteorites |journal=Surveys in Geophysics |date=2002 |volume=23 |issue=5 |page=414 |doi=10.1023/A:1020139302770}}</ref>

In January 2020, [[Chemistry:Cosmochemistry|cosmochemists]] reported that the [[Physics:Oldest dated rocks|oldest material]] found on Earth to date are the [[Chemistry:Silicon carbide|silicon carbide]] particles from the Murchison meteorite, which have been determined to be 7&nbsp;billion years old, about 2.5&nbsp;billion years [[Astronomy:Chronology of the universe|older than]] the 4.54-billion-year [[Earth:Age of the Earth|age of the Earth]] and the [[Astronomy:Formation and evolution of the Solar System|Solar System]].{{efn|That makes the stardust grains in the Murchison meteorite [[Astronomy:Presolar grains|presolar grains]], since they originated at a time before the [[Astronomy:Sun|Sun]] was formed.}} The published study noted that "dust lifetime estimates mainly rely on sophisticated theoretical models. These models, however, focus on the more common small dust grains and are based on assumptions with large uncertainties."<ref name="PNAS-20200113" />

==History==
On 28 September 1969 at approximately 10:58 a.m. local time, near Murchison, Victoria, in Australia, a bright [[Astronomy:Meteoroid#Fireball|fireball]] was observed to separate into three fragments before disappearing,<ref name="database" /> leaving a cloud of smoke. About 30 seconds later, a tremor was heard. Many fragments were found scattered over an area larger than {{convert|13|km²}}, with individual mass up to {{convert|7|kg}}; one, weighing {{convert|680|g|lb|1}}, broke through a roof and fell in hay.<ref name="database" /> The total collected mass of the meteorite exceeds {{convert|100|kg|-1}}.<ref>Pepper, F. [https://www.abc.net.au/news/science/2019-10-02/murchison-meteorite-50th-anniversary-1969-science-geology/11528644 When a space visitor came to country Victoria] {{Webarchive|url=https://web.archive.org/web/20191001225750/https://www.abc.net.au/news/science/2019-10-02/murchison-meteorite-50th-anniversary-1969-science-geology/11528644 |date=1 October 2019 }} ''ABC News'', 2 October 2019. Retrieved 2 October 2019.</ref>

==Classification and composition==
The meteorite belongs to the CM group of carbonaceous chondrites. Like most CM chondrites, Murchison is [[Astronomy:Chondrite#Petrologic types|petrologic type 2]], which means that it experienced extensive alteration by water-rich fluids on its [[Astronomy:Parent body|parent body]]<ref>{{cite journal |last1=Airieau |first1=S. A. |last2=Farquhar |first2=J. |last3=Thiemens |first3=M. H. |last4=Leshin |first4=L. A. |last5=Bao |first5=H. |last6=Young |first6=E. |doi=10.1016/j.gca.2005.01.029 |title=Planetesimal sulfate and aqueous alteration in CM and CI carbonaceous chondrites |journal=Geochimica et Cosmochimica Acta |volume=69 |issue=16 |pages=4167–4172 |date=2005 |bibcode=2005GeCoA..69.4167A |citeseerx=10.1.1.424.6561 }}
<!-- NOT THE SAME PAPER! |url=http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1230.pdf |format=PDF it's this paper : http://adsabs.harvard.edu/abs/2007LPI....38.1230R  Progressive Alteration of CM Chondrites: Effects on Refractory Inclusions -->
</ref> before falling to Earth. CM chondrites, together with the CI group, are rich in [[Chemistry:Carbon|carbon]] and are among the most chemically primitive meteorites.<ref>{{cite web |url=http://www.psrd.hawaii.edu/PSRDglossary.html |title=Planetary Science Research Discoveries: Glossary |access-date=24 January 2012 |archive-url=https://web.archive.org/web/20120124211721/http://www.psrd.hawaii.edu/PSRDglossary.html |archive-date=24 January 2012 |url-status=live }}</ref> Like other CM chondrites, Murchison contains abundant calcium-aluminium-rich inclusions. More than 15 [[Chemistry:Amino acid|amino acid]]s, some of the basic components of life, have been identified during multiple studies of this meteorite.<ref name="Kvenvolden">{{cite journal |title=Nonprotein Amino Acids from Spark Discharges and Their Comparison with the Murchison Meteorite Amino Acids |last1=Wolman |first1=Yecheskel |last2=Haverland |first2=William J. |last3=Miller |first3=Stanley L. |journal=Proceedings of the National Academy of Sciences|volume=69 |issue=4 |pages=809–811 |date=April 1972 |pmc=426569 |pmid=16591973 |doi=10.1073/pnas.69.4.809|bibcode = 1972PNAS...69..809W |doi-access=free }}</ref>

In January 2020, astronomers reported that Murchison meteorite [[Chemistry:Silicon carbide|silicon carbide]] particles had been determined to be 7 billion years old, 2.5 billion years older than the 4.54 billion years [[Earth:Age of the Earth|age of the Earth]] and the [[Astronomy:Formation and evolution of the Solar System|Solar System]], and the [[Physics:Oldest dated rocks|oldest material]] found on Earth to date.<ref name="LS-20200113">{{cite news |last=Weisberger |first=Mindy |title=7 Billion-Year-Old Stardust Is Oldest Material Found on Earth - Some of these ancient grains are billions of years older than our sun. |url=https://www.livescience.com/oldest-material-on-earth.html |date=13 January 2020 |work=Live Science |access-date=13 January 2020 |archive-url=https://web.archive.org/web/20200114030808/https://www.livescience.com/oldest-material-on-earth.html |archive-date=14 January 2020 |url-status=live }}</ref><ref name="PNAS-20200113">{{cite journal |last1=Heck |first1=Philipp R. |last2=Greer |first2=Jennika |last3=Kööp |first3=Levke |last4=Trappitsch |first4=Reto |last5=Gyngard |first5=Frank |last6=Busemann |first6=Henner |last7=Maden |first7=Colin |last8=Ávila |first8=Janaína N. |last9=Davis |first9=Andrew M. |last10=Wieler |first10=Rainer |title=Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide |journal=Proceedings of the National Academy of Sciences |pages=1884–1889 |date=13 January 2020 |volume=117 |issue=4 |doi=10.1073/pnas.1904573117 |pmid=31932423 |pmc=6995017 |bibcode=2020PNAS..117.1884H |doi-access=free }}</ref>

==Organic compounds==
[[File:Murchison-meteorite-ANL.jpg|thumb|Fragment of the Murchison meteorite (at right) and isolated individual particles (shown in the test tube)]]

Murchison contains common [[Chemistry:Amino acid|amino acid]]s such as [[Chemistry:Glycine|glycine]], [[Chemistry:Alanine|alanine]], and [[Chemistry:Glutamic acid|glutamic acid]] as well as unusual ones such as [[Chemistry:Isovaline|isovaline]] and [[Chemistry:Leucines|pseudoleucine]].<ref>{{cite journal |title=Evidence for extraterrestrial amino-acids and hydrocarbons in the Murchison meteorite |last1=Kvenvolden |first1=Keith A. |last2=Lawless |first2=James |last3=Pering |first3=Katherine |last4=Peterson |first4=Etta |last5=Flores |first5=Jose |last6=Ponnamperuma |first6=Cyril |last7=Kaplan |first7=Isaac R. |last8=Moore |first8=Carleton |journal=Nature |volume=228 |issue=5275 |pages=923–926 |date=1970 |url=http://chemport.cas.org/cgi-bin/sdcgi?APP=ftslink&action=reflink&origin=npg&version=1.0&coi=1:CAS:528:DyaE3MXisVCnsg%3D%3D&pissn=0028-0836&pyear=1983&md5=cb8b015f54156458fa2be8cdca44789f |doi=10.1038/228923a0 |pmid=5482102 |bibcode=1970Natur.228..923K |s2cid=4147981 }}</ref> A complex mixture of [[Chemistry:Alkane|alkane]]s was isolated as well, similar to that found in the [[Biology:Miller–Urey experiment|Miller–Urey experiment]]. [[Chemistry:Serine|Serine]] and [[Chemistry:Threonine|threonine]], usually considered to be earthly contaminants, were conspicuously absent in the samples. A specific family of amino acids called [[Biology:Diamino acid|diamino acid]]s was identified in the Murchison meteorite as well.<ref>{{cite journal |title=Identification of diamino acids in the Murchison meteorite |last1=Meierhenrich |first1=Uwe J. |journal=PNAS |volume=101 |pages=9182–9186 |date=2004 |doi=10.1073/pnas.0403043101 |pmid=15194825 |issue=25 |pmc=438950 |bibcode=2004PNAS..101.9182M |last2=Bredehöft |first2=Jan Hendrik |last3=Jessberger |first3=Elmar K. |last4=Thiemann |first4=Wolfram H.-P. |doi-access=free }}</ref>

The initial report stated that the amino acids were racemic and therefore formed in an abiotic manner, because amino acids of terrestrial [[Biology:Protein|protein]]s are all of the L-configuration. Later the amino acid [[Chemistry:Alanine|alanine]], which is also a protein amino acid, was found to have an excess of the L-configuration,<ref>{{cite journal |title=Distribution and enantiomeric composition of amino acids in the Murchison meteorite |last1=Engel |first1=Michael H. |last2=Nagy |first2=Bartholomew |journal=Nature |volume=296 |pages=837–840 |date=29 April 1982 |doi=10.1038/296837a0 |issue=5860 |bibcode=1982Natur.296..837E |s2cid=4341990 }}</ref> which led several scientists to suspect terrestrial contamination according to the argument that it would be "unusual for an abiotic [[Chemistry:Stereoselectivity|stereoselective]] decomposition or synthesis of amino acids to occur with protein amino acids but not with non-protein amino acids".<ref>{{cite journal |title=On the reported optical activity of amino acids in the Murchison meteorite |last1=Bada |first1=Jeffrey L. |last2=Cronin |first2=John R. |last3=Ho |first3=Ming-Shan |last4=Kvenvolden |first4=Keith A. |last5=Lawless |first5=James G. |last6=Miller |first6=Stanley L. |last7=Oro |first7=J. |last8=Steinberg |first8=Spencer |journal=Nature |volume=301 |pages=494–496 |date=10 February 1983 |doi=10.1038/301494a0 |issue=5900 |bibcode=1983Natur.301..494B |s2cid=4338550 }}</ref> In 1997, L-excesses also were found in a non-protein amino acid, [[Chemistry:Isovaline|isovaline]],<ref>{{cite journal |last1=Cronin |first1=John R. |last2=Pizzarello |first2=S. |title=Enantiomeric excesses in meteoritic amino acids |journal=Science |date=1997 |volume=275 |pages=951–955 |doi=10.1126/science.275.5302.951 |pmid=9020072 |issue=5302|bibcode = 1997Sci...275..951C |s2cid=10979716 }}</ref> suggesting an extraterrestrial source for molecular asymmetry in the [[Astronomy:Solar System|Solar System]]. At the same time, L-excesses of [[Chemistry:Alanine|alanine]] were found in Murchison, but with enrichment in the [[Physics:Isotope|isotope]] {{Nitrogen|3=15}},<ref>{{cite journal |title=Isotopic evidence for extraterrestrial non-racemic amino acids in the Murchison meteorite |last1=Engel |first1=Michael H. |last2=Macko |first2=S. A. |journal=Nature |volume=389 |pages=265–268 |date=1 September 1997 |doi=10.1038/38460 |pmid=9305838 |issue=6648 |bibcode=1997Natur.389..265E |s2cid=4411982 }}</ref> however, the isotopic pairing was contested later, on analytical grounds.<ref>{{cite journal |last1=Pizzarello |first1=Sandra |last2=Cronin |first2=JR |title=Alanine enantiomers in the Murchison meteorite |journal=Nature |date=1998 |volume=394 |page=236 |doi=10.1038/28306 |pmid=9685155 |issue=6690|bibcode = 1998Natur.394..236P |s2cid=4424928 |doi-access=free }}</ref> By 2001, the list of organic materials identified in the meteorite was extended to [[Chemistry:Polyol|polyol]]s.<ref>{{cite journal |title=Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth |last1=Cooper |first1=George |last2=Kimmich |first2=Novelle |last3=Belisle |first3=Warren |last4=Sarinana |first4=Josh |last5=Brabham |first5=Katrina |last6=Garrel |first6=Laurence |journal=Nature |volume=414 |pages=879–883 |date=20 December 2001 |doi=10.1038/414879a |pmid=11780054 |issue=6866 |bibcode=2001Natur.414..879C |s2cid=199294 |url=https://zenodo.org/record/1233202 |access-date=2 July 2019 |archive-url=https://web.archive.org/web/20200116010831/https://zenodo.org/record/1233202 |archive-date=16 January 2020 |url-status=live |doi-access=free }}</ref>

{|class="wikitable" border="1" align="right" style="margin-left:8px;"
|- style="background:#efefef;"
! '''Compound class'''<ref>{{cite journal |title=Organic Molecules in Comets and Meteorites and Life on Earth |journal=Department of Physics and Astronomy |publisher=[[Organization:Johns Hopkins University|Johns Hopkins University]] |date=17 February 2007 |first=Pavel |last=Machalek |url=http://www.pha.jhu.edu/~pmachal2/ism_review_redone_feb07.pdf |access-date=7 October 2008 |url-status=dead |archive-url=https://web.archive.org/web/20081217021057/http://www.pha.jhu.edu/~pmachal2/ism_review_redone_feb07.pdf |archive-date=17 December 2008 }}</ref> !! '''Concentration ([[Parts per million|ppm]])'''
|-
|Amino acids &nbsp;|| 17–60
|-
|Aliphatic hydrocarbons || >35
|-
|Aromatic hydrocarbons || 3319
|-
|Fullerenes || >100
|-
|Carboxylic acids || >300
|-
|Hydrocarboxylic acids || 15
|-
|Purines and pyrimidines || 1.3
|-
|Alcohols || 11
|-
|Sulfonic acids || 68
|-
|Phosphonic acids || 2
|-
|'''Total''' || >3911.3
|}

The meteorite contained a mixture of left-handed and right-handed amino acids; most amino acids used by living organisms are left-handed in [[Biology:Chirality#In biochemistry|chirality]], and most sugars used are right-handed. A team of chemists in Sweden demonstrated in 2005 that this [[Physics:Homochirality|homochirality]] could have been triggered or catalyzed, by the action of a left-handed amino acid such as [[Chemistry:Proline|proline]].<ref>{{cite journal |title=Plausible origins of homochirality in the amino acid catalyzed neogenesis of carbohydrates |last1=Córdova |first1=Armando |last2=Engqvist |first2=Magnus |last3=Ibrahem |first3=Ismail |last4=Casas |first4=Jesús |last5=Sundén |first5=Henrik |journal=Chem. Commun. |pages=2047–2049 |date=2005 |doi=10.1039/b500589b |pmid=15834501 |issue=15 }}</ref>

Several lines of evidence indicate that the interior portions of well-preserved fragments from Murchison are pristine. A 2010 study using high resolution analytical tools including [[Physics:Spectroscopy|spectroscopy]], identified 14,000 molecular compounds, including 70 amino acids, in a sample of the meteorite.<ref>{{cite news |first=Doreen |last=Walton |title=Space rock contains organic molecular feast |date=15 February 2010 |url=http://news.bbc.co.uk/2/hi/science/nature/8516319.stm |work=BBC News |access-date=15 February 2010 |archive-url=https://web.archive.org/web/20100216052616/http://news.bbc.co.uk/2/hi/science/nature/8516319.stm |archive-date=16 February 2010 |url-status=live }}</ref><ref>{{cite journal |title=High molecular diversity of extraterrestrial organic matter in Murchison meteorite revealed 40 years after its fall |journal=PNAS |volume=107 |pages=2763–2768 |date=16 February 2010 |first1=Philippe |last1=Schmitt-Kopplin |first2=Zelimir |last2=Gabelica |first3=Régis D. |last3=Gougeon |first4=Agnes |last4=Fekete |first5=Basem |last5=Kanawati |first6=Mourad |last6=Harir |first7=Istvan |last7=Gebefuegi |first8=Gerhard |last8=Eckel |first9=Norbert |last9=Hertkorn |url=http://www.pnas.org/content/early/2010/02/12/0912157107.full.pdf+html |format=PDF |doi=10.1073/pnas.0912157107 |pmid=20160129 |issue=7 |pmc=2840304 |bibcode=2010PNAS..107.2763S |access-date=16 February 2010 |archive-url=https://web.archive.org/web/20121202013703/http://www.pnas.org/content/early/2010/02/12/0912157107.full.pdf+html |archive-date=2 December 2012 |url-status=live |doi-access=free }}</ref> The limited scope of the analysis by [[Physics:Mass spectrometry|mass spectrometry]] provides for a potential 50,000 or more unique molecular compositions, with the team estimating the possibility of millions of distinct organic compounds in the meteorite.<ref>{{cite news |first=John |last=Matson |title=Meteorite That Fell in 1969 Still Revealing Secrets of the Early Solar System |date=15 February 2010 |publisher=Scientific American |url=http://www.scientificamerican.com/article.cfm?id=murchison-meteorite |access-date=15 February 2010 |archive-url=https://web.archive.org/web/20110319025453/http://www.scientificamerican.com/article.cfm?id=murchison-meteorite |archive-date=19 March 2011 |url-status=live }}</ref>

===Nucleobases===
{{Further|Biology:Nucleobase}}

Measured [[Chemistry:Purine|purine]] and [[Chemistry:Pyrimidine|pyrimidine]] compounds were found in the Murchison meteorite. Carbon [[Chemistry:Isotope-ratio mass spectrometry|isotope ratio]]s for [[Chemistry:Uracil|uracil]] and [[Chemistry:Xanthine|xanthine]] of [[Biology:Δ13C|δ<sup>13</sup>C]] = +44.5‰ and +37.7‰, respectively, indicate a non-terrestrial origin for these compounds. This specimen demonstrates that many [[Chemistry:Organic compound|organic compound]]s could have been delivered by early solar system bodies and may have played a key role in [[Biology:Abiogenesis|life's origin]].<ref>{{cite journal |title=Extraterrestrial nucleobases in the Murchison meteorite |journal=Earth and Planetary Science Letters |date=20 March 2008 |first1=Zita |last1=Martins |first2=Oliver |last2=Botta |first3=Marilyn L. |last3=Fogel |first4=Mark A. |last4=Sephton |first5=Daniel P. |last5=Glavin |first6=Jonathan S. |last6=Watson |first7=Jason P. |last7=Dworkin |first8=Alan W. |last8=Schwartz |first9=Pascale |last9=Ehrenfreund|author-link3=Marilyn Fogel |author-link9=Pascale Ehrenfreund |volume=270 |issue=1–2 |pages=130–136 |url=http://astrobiology.gsfc.nasa.gov/analytical/PDF/Martinsetal2008.pdf |access-date=7 October 2008 |doi=10.1016/j.epsl.2008.03.026 |bibcode=2008E&PSL.270..130M |arxiv=0806.2286 |s2cid=14309508 |archive-url=https://web.archive.org/web/20110810095031/http://astrobiology.gsfc.nasa.gov/analytical/PDF/Martinsetal2008.pdf |archive-date=10 August 2011 |url-status=dead}}</ref>

==See also==
* [[Chemistry:Cosmochemistry|Cosmochemistry]]
* [[Astronomy:Glossary of meteoritics|Glossary of meteoritics]]
* [[Biology:Panspermia|Panspermia]]

==Notes==
{{noteslist}}

==References==
{{Reflist|30em}}

==External links==
* {{cite web |url=http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=375 |title=Murchison's Amino Acids: Tainted Evidence? |first=Anne M. |last=Rosenthal |date=12 February 2003 |publisher=Astrobiology Magazine}}
* {{cite web |url=http://www.scientificamerican.com/article.cfm?id=murchison-meteorite |title=Meteorite That Fell in 1969 Still Revealing Secrets of the Early Solar System |first=John |last=Matson |date=15 February 2010 |publisher=Scientific American}}

{{NASA}}
{{Extraterrestrial life}}
{{Modern impact events}}
[[Category:Origin of life]]
[[Category:Astrobiology]]

{{Sourceattribution|Murchison meteorite|1}}