Great Replacement

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https://en.wikipedia.org/wiki/Great_Replacement 

The Great Replacement (French: Grand Remplacement), also known as replacement theory or great replacement theory, is a white nationalist far-right conspiracy theory disseminated by French author Renaud Camus. The original theory states that, with the complicity or cooperation of "replacist" elites, the ethnic French and white European populations at large are being demographically and culturally replaced with non-white peoples—especially from Muslim-majority countries—through mass migration, demographic growth and a drop in the birth rate of white Europeans. Since then, similar claims have been advanced in other national contexts, notably in the United States. Mainstream scholars have dismissed these claims as rooted in a misunderstanding of demographic statistics and premised upon an unscientific, racist worldview. According to the Encyclopædia Britannica, the Great Replacement "has been widely ridiculed for its blatant absurdity."

While similar themes have characterized various far-right theories since the late 19th century, the particular term was popularized by Camus in his 2011 book Le Grand Remplacement. The book associates the presence of Muslims in France with danger and destruction of French culture and civilization. Camus and other conspiracy theorists attribute recent demographic changes in Europe to intentional policies advanced by global and liberal elites (the "replacists") from within the Government of France, the European Union, or the United Nations; they describe it as a "genocide by substitution".

The conspiracy theory found support in Europe, and has also grown popular among anti-migrant and white nationalist movements from other parts of the West; many of their adherents maintain that "immigrants [are] flocking to predominantly white countries for the precise purpose of rendering the white population a minority within their own land or even causing the extinction of the native population". It aligns with (and is a part of) the larger white genocide conspiracy theory except in the strategic replacement of antisemitic canards with Islamophobia. This replacement, along with a use of simple catch-all slogans, have been cited as reasons for its broader appeal in a pan-European context, although the concept remains rooted in antisemitism in many white nationalist movements, especially (but not exclusively) in the United States.

Although Camus has publicly condemned white nationalist violence, scholars have argued that calls to violence are implicit in his depiction of non-white migrants as an existential threat to white populations. Several far-right terrorists, including the perpetrators of the 2019 Christchurch mosque shootings, the 2019 El Paso shooting and the 2022 Buffalo shooting, have made reference to the "Great Replacement" conspiracy theory. American conservative media personalities, including Tucker Carlson and Laura Ingraham, have espoused ideas of a replacement. Some Republican politicians have endorsed the theory in order to appeal to far-right members of the Republican Party and as a way of signalling their loyalty to Donald Trump.

Background

Renaud Camus developed his conspiracy theory in two books published in 2010 and 2011, in the context of an increase in anti-immigrant rhetoric in public discourse during the previous decade. Europe also experienced an escalation in Islamic terrorist attacks during the 2000s–2010s, and a migrant crisis that began in 2015, which exacerbated tensions and prepared public opinion for the reception of Camus's conspiracy theory. As the latter depicts a population replacement said to occur in a short time lapse of one or two generations, the migrant crisis was particularly conducive to the spread of Camus's ideas while the terrorist attacks accelerated the construction of immigrants as an existential threat among those who shared such a worldview.

Camus's theme of a future demise of European culture and civilization also parallels a "cultural pessimistic" and anti-Islam trend among European intellectuals of the period, illustrated in several best-selling and straightforwardly titled books released during the 2010s: Thilo Sarrazin's Germany Abolishes Itself (2010), Éric Zemmour's The French Suicide (2014) or Michel Houellebecq's Submission (2015).

Concept of Renaud Camus

Author Renaud Camus, progenitor of the "Great Replacement" conspiracy theory, September 2013.

The "Great Replacement" conspiracy theory was developed by French author Renaud Camus, initially in a 2010 book titled L'Abécédaire de l'in-nocence ("Abecedarium of no-harm"), and the following year in an eponymous book, Le Grand Remplacement (introduction au remplacisme global). Camus has claimed that the name Grand Remplacement "came to [him], almost by chance, perhaps in a more or less unconscious reference to the Grand Dérangement of the Acadians in the 18th century." Commenting on the name, he has also declared that his theory was the "implementation in real life" of Bertolt Brecht's quip from the satirical poem Die Lösung that the easiest thing to do for a government was to change the people had the people forfeited its confidence.

According to Camus, the "Great Replacement" has been nourished by "industrialisation", "despiritualisation" and "deculturation"; the materialistic society and globalism having created a "replaceable human, without any national, ethnic or cultural specificity", what he labels "global replacism". Camus claims that "the great replacement does not need a definition," as the term is not, in his views, a "concept" but rather a "phenomenon".

In Camus's theory, the indigenous French people ("the replaced") is described as being demographically replaced by non-white populations ("the replacing [peoples]")—mainly coming from Africa or the Middle East—in a process of "peopling immigration" encouraged by a "replacist power".

Camus frequently uses terms and concepts related to the period of Nazi-occupied France (1940–1945). He for instance labels "colonizers" or "Occupiers" people of non-European descent who reside in Europe, and dismisses what he calls the "replacist elites" as "collaborationist". Camus founded in 2017 an organization named the National Council of European Resistance, in a self-evident reference to the World War II National Council of the Resistance (1943–1945). This analogy to the French Resistance against Nazism has been described as an implicit call to hatred, direct action or even violence against what Camus labels the "Occupiers; i.e. the immigrants". Camus has also compared the Great Replacement and the so-called "genocide by substitution" of the European peoples to the Holocaust.

Claimed influences

See also: The Camp of the Saints and Rivers of Blood speech

Camus cites two influential figures in the epilogue of his 2011 book The Great Replacement: British politician Enoch Powell's apocalyptic vision of future race relations—expressed in his 1968 "Rivers of Blood" speech—and French author Jean Raspail's depiction of the collapse of the West from an overwhelming "tidal wave" of Third World immigration, featured in his 1973 novel The Camp of the Saints.

Camus also declared to The Spectator magazine in 2016 that a key to understanding the "Great Replacement" can be found in his 2002 book Du Sens. In the latter he wrote that the words "France" and "French" equal a natural and physical reality rather than a legal one, in a cratylism similar to Charles Maurras's distinction between the "legal" and the "real country". During the same interview, Camus mentioned that he began to imagine his conspiracy theory back in 1996, during the redaction of a guidebook on the department of Hérault, in the South of France: "I suddenly realized that in very old villages [...] the population had totally changed too [...] this is when I began to write like that."

Similar themes

Main article: White genocide conspiracy theory

Despite its own singularities and concepts, the "Great Replacement" is encompassed in a larger and older "white genocide" conspiracy theory, popularized in the US by neo-Nazi David Lane in his 1995 White Genocide Manifesto, where he asserted that governments in Western countries were intending to turn white people into "extinct species".

The idea of "replacement" under the guidance of a hostile elite can be further traced back to pre-WWII antisemitic conspiracy theories which posited the existence of a Jewish plot to destroy Europe through miscegenation, especially in Édouard Drumont's antisemitic bestseller La France juive (1886). Commenting on this resemblance, historian Nicolas Lebourg and political scientist Jean-Yves Camus suggest that Camus's contribution was to replace the antisemitic elements with a clash of civilizations between Muslims and Europeans. Also in the late 19th century, imperialist politicians invoked the Péril jaune (Yellow Peril) in their negative comparisons of France's low birth-rate and the high birth-rates of Asian countries. From that claim arose an artificial, cultural fear that immigrant-worker Asians soon would "flood" France. This danger supposedly could be successfully countered only by increased fecundity of French women. Then, France would possess enough soldiers to thwart the eventual flood of immigrants from Asia. Maurice Barrès's nationalist writings of that period have also been noted in the ideological genealogy of the "Great Replacement", Barrès contending both in 1889 and in 1900 that a replacement of the native population under the combined effect of immigration and a decline in the birth rate was happening in France.

Scholars also highlight a modern similarity to European neo-fascist and neo-Nazi thinkers from the immediate post-war, especially Maurice Bardèche, René Binet and Gaston-Armand Amaudruz, and to concepts advanced from the 1960s onward by the French Nouvelle Droite.

The associated and more recent conspiracy theory of "Eurabia", published by British author Bat Ye'or in her 2005 eponymous book, is often cited as a probable inspiration for Camus's "Great Replacement". Eurabia theory likewise involves globalist entities, that time led by both French and Arab powers, conspiring to Islamize Europe, with Muslims submerging the continent through immigration and higher birth rates. The conspiracy theory also depicts immigrants as invaders or as a fifth column, invited to the continent by a corrupt political elite. Scholars generally agree that, although he did not father the theme, Camus indeed coined the term "Great Replacement" as a slogan and concept, and eventually led it to its fame in the 2010s.

Analysis

Demographic statistics

While the ethnic demography of France has shifted as a result of post-WWII immigration, scholars have generally dismissed the claims of a "great replacement" as being rooted in an exaggeration of immigration statistics and unscientific, racially prejudiced views. Geographer Landis MacKellar criticized Camus's thesis for assuming "that third- and fourth- generation 'immigrants' are somehow not French." Researchers have variously estimated the Muslim population of France at between 8.8% and 12.5% in 2017, making a "replacement" unlikely according to MacKellar.

Racial connotations

In the words of scholar Andrew Fergus Wilson, whereas the islamophobic Great Replacement theory can be distinguished from the parallel antisemitic white genocide conspiracy theory, "they share the same terms of reference and both are ideologically aligned with the so-called '14 words' of David Lane [We must secure the existence of our people and a future for white children]." In 2021, the Anti-Defamation League wrote that "since many white supremacists, particularly those in the United States, blame Jews for non-white immigration to the U.S.", the Great Replacement theory has been increasingly associated with antisemitism and conflated with the white genocide conspiracy theory. Scholar Kathleen Belew has argued that the Great Replacement theory "allows an opportunism in selecting enemies", but "also follows the central motivating logic, which is to protect the thing on the inside [i.e. the preservation and birth rate of the white race], regardless of the enemy on the outside."

According to Australian historian A. Dirk Moses, the great replacement theory is a form of psychological projection in which Europeans—who enacted settler-colonial projects entailing the elimination and replacement of native populations by settler societies—fear the reverse may happen to them.

In German discourse, Austrian political scientist Rainer Bauböck questioned the conspiracy theorists' use of the terms "population replacement" or "exchange" ("Bevölkerungsaustausch"). Using Ruth Wodak's analysis that the slogan needs to be viewed in its historical context, Bauböck has concluded that the conspiracy theory is a reemergence of the Nazi ideology of Umvolkung ("ethnicity inversion").

Popularity

Camus's tract for his 2014 "day of anger" demonstration against the "great replacement": "No to the change of people and of civilization, no to antisemitism"

The simplicity and use of catch-all slogans in Camus's formulations—"you have one people, and in the space of a generation you have a different people"—as well as his removal of antisemitism from the original neo-Nazi "white genocide" conspiracy theory, have been cited as conducive to the popularity of the "Great Replacement" in Europe.

In a survey led by Ifop in December 2018, 25% of the French subscribed to the conspiracy theory; as well as 46% of the responders who defined themselves as "Gilets Jaunes" (Yellow Vest protesters). In another survey led by Harris Interactive in October 2021, 61% of the French believed that the "Great Replacement" will happen in France; 67% of the respondents were worried about it.

The theory has also become influential in far-right and white nationalist circles outside of France. The conspiracy theory has been cited by Canadian far-right political activist Lauren Southern in a YouTube video of the same name released in July 2017. Southern's video had attracted in 2020 more than 686,000 viewers and is credited with helping to popularize the conspiracy theory. Counter-jihad Norwegian blogger Fjordman has also participated in spreading the theory.

Prominent right-wing extremist websites such as Gates of Vienna, Politically Incorrect, and Fdesouche [fr] have provided a platform for bloggers to diffuse and popularize the theory of the "Great Replacement". Among its main promoters are also a wide-ranging network of loosely connected white nationalist movements, especially the Identitarian movement in Europe, and other groups like PEGIDA in Germany.

Political influence

Europe

France

Much of the European spread of the Great Replacement (French: Grand Remplacement) conspiracy theory rhetoric is due to its prevalence in French national discourse and media. Nationalist right-wing groups in France have asserted that there is an ongoing "Islamo-substitution" of the indigenous French population, associating the presence of Muslims in France with potential danger and destruction of French culture and civilization.

In 2011, Marine Le Pen evoked the theory, claiming that France's "adversaries" were waging a moral and economic war on the country, apparently "to deliver it to submersion by an organized replacement of our population". In 2013, historian Dominique Venner's suicide in Notre-Dame de Paris, in which he left a note outlining the "crime of the replacement of our people" is reported to have inspired the far-right Iliade Institute's main ideological tenet of the Great Replacement. Referring to the conspiracy theory, Marine Le Pen publicly praised Venner, claiming that his "last gesture, eminently political, was to try to awaken the French people".

In 2015, Guillaume Faye gave a speech at the Swedish Army Museum in Stockholm, in which he claimed there were three societal things being used against Europeans to carry out a supposed Great Replacement: abortion, homosexuality and immigration. He asserted that Muslims were replacing white people by using birthrates as a demographic weapon.

In June 2017, a BuzzFeed investigation revealed three National Front candidates subscribing to the conspiracy theory ahead of the legislative elections. These included Senator Stéphane Ravier's personal assistant, who claimed the Great Replacement had already started in France. Publishing an image of blonde girl next to the caption "Say no to white genocide", Ravier's aide politically charged the concept further, writing "the National Front or the invasion".

Journalist and author Éric Zemmour, who ran for President of France in the 2022 election, promoted extensively the Great Replacement concept.

By September 2018, in a meeting at Fréjus, Marine Le Pen closely echoed Great Replacement rhetoric. Speaking of France, she declared that "never in the history of mankind, have we seen a society that organizes an irreversible submersion" that would eventually cause French society to "disappear by dilution or substitution, its culture and way of life". Former National Assembly delegate Marion Maréchal, who is a junior member of the political Le Pen family, is also a proponent of the theory. In March 2019, in a trip to the U.S., Maréchal evoked the theory, stating "I don't want France to become a land of Islam". Insisting that the Great Replacement was "not absurd", she declared the "indigenous French" people, apparently in danger of being a minority by 2040, now wanted their "country back".

National Rally's serving president Marine Le Pen, who is the aunt of Maréchal, has been heavily influenced by the Great Replacement. FAZ newspaper has described the conspiracy theory creator Renaud Camus as Le Pen's "whisperer". In May 2019, National Rally spokesman Jordan Bardella was reported to use the conspiracy theory during a televised debate with Nathalie Loiseau, after he argued that France must "turn off the tap" from the demographic bomb of African immigration into the country.

In June 2019, journalist and author Éric Zemmour pushed the concept in comparison to the Kosovo War, claiming "In 1900, there were 90% Serbs and 10% Muslims in Kosovo, in 1990 there were 90% Muslims and 10% Serbs, then there was war and the independence of Kosovo". Zemmour, author of The French Suicide, has repeatedly described "the progressive replacement, over a few decades, of the historic population of our country by immigrants, the vast majority of them non-European". Later that month, Marion Maréchal joined Zemmour in invoking the Great Replacement in relation to the Balkan region, stating "I do not want my France to become Kosovo" and declared that the changing demographics of France "threatens us" ("nous menace") and that this was increasingly clear. Zemmour ran for President in 2022 and continued to extensively promote the theory during his campaign. He finished in fourth place in the first round of the election, taking 7,07% of the vote.

Austria

See also: Kalergi plan

Identitäre Bewegung Österreich (IBÖ), the Austrian branch of the Identitarian movement, promotes this theory, citing a "great exchange" or replacement of the population that supposedly needs to be reversed. In April 2019, Heinz-Christian Strache campaigning for his FPÖ party ahead of the 2019 European Parliament election endorsed the conspiracy theory. Claiming that "population replacement" in Austria was a real threat, he stated that "We don't want to become a minority in our own country". Compatriot Martin Sellner, who also supports the theory, celebrated Strache's political use of the Great Replacement.

Belgium

In September 2018, Schild & Vrienden [nl], an extremist Flemish youth organization, were reported to be endorsing the conspiracy theory. The group, claiming that native populations of Europe were being replaced by migrants; they proposed an end to all immigration, forced deportation of non-whites, and the founding of ethnostates. The following month, VRT detailed how the organization was discussing the Great Replacement on secretive chat channels, and using the conspiracy theory to promote Flemish ethnic identity.

In March 2019, Flemish nationalist Dries Van Langenhove of the Vlaams Belang party repeatedly stated that the Flemish people were "being replaced" in Belgium, posting claims on social media which endorsed the Great Replacement theory.

Denmark

Use of the Great Replacement (Danish: Store Udskiftning) conspiracy theory has become common in right-wing Danish political rhetoric. In April 2019, Rasmus Paludan, leader of the Hard Line party, which is widely associated with the Great Replacement, claimed that by the year 2040 ethnic Danish people would be approaching to be a minority in Denmark, having been outnumbered by Muslims and their descendants. During a debate for the 2019 European Parliament elections, Paludan used the concept to justify a proposal to ban Muslim immigration and deport all Islamic residents from the country, in what Le Monde described as Paludan "preaching the 'great replacement theory'".

In June 2019, Pia Kjærsgaard invoked the conspiracy theory while serving as Speaker of the Danish Parliament. After the alleged encouragement of Muslim communities to "vote red", for the Social Democrats; Kjærsgaard asked "What will happen? A replacement of the Danish people?".

Germany

Ex-SPD politician Thilo Sarrazin is reported to be one of the most influential promoters of the Great Replacement, having published several books on the subject, some of which, such as Germany Abolishes Itself, are in high circulation. Sarrazin has proposed that there are too many immigrants in Germany, and that they supposedly have lower IQs than Germans. Regarding the demographics of Germany, he has claimed that in a century ethnic Germans will drop in number to 25 million, in 200 years to eight million and in 300 years: three million.

In May 2016, Alternative for Germany (German: Alternative für Deutschland, AfD) deputy leader Beatrix von Storch used a language reminiscent of the theory when she claimed that plans for a mass exchange of populations ("Massenaustausch der Bevölkerung") had long been made.

In April 2017, a few months before he assumed the leadership of the AfD, Alexander Gauland released a press statement regarding the issue of family reunification for refugees, in which he claimed that "Population exchange in Germany is running at full speed". In October 2018, following Beatrix von Storch's lead, Bundestag member Petr Bystron said the Global Compact for Migration was part of the conspiracy to bring about systemic population change in Germany.

In March 2019, Vice Germany reported how AfD MP Harald Laatsch [de] attempted to justify and assign blame for the Christchurch mosque shootings, in relation to his "The Great Exchange" theory, by asserting that the shooter's actions were driven by "overpopulation" from immigrants and "climate protection" against them. Laatsch also claimed that the climate movement, who he labelled "climate panic propagators", had a "shared responsibility" for the massacre, and singled out child activist Greta Thunberg.

Similarly, right-wing publicist Martin Lichtmesz [de] denied that either Anders Behring Breivik's 2011 manifesto, which referred to the Eurabia variant of the "white genocide" narrative, or Brenton Tarrant's 2019 The Great Replacement manifesto, had any connection to the theory. Claiming that it was, in fact, not a conspiracy theory at all, Lichtmesz said both Breivik and Tarrant were reacting to a real phenomenon; a "historically unique experiment" of a "Great Exchange" of people.

Hungary

Prime Minister Viktor Orbán and his political party Fidesz in Hungary have been associated with the conspiracy theory over the course of several years. The Sydney Morning Herald detailed Orbán's belief in and promotion of the Great Replacement as being central to the modern right-wing politics of Europe. In December 2018, he claimed the "Christian identity of Europe" needed saving, and labelled refugees traveling to Europe as "Muslim invaders". In a speech, Orbán asserted: "If in the future Europe is to be populated by people other than Europeans, and we accept this as a fact and see it as natural, then we will effectively be consenting to population replacement: to a process in which the European population is replaced".

He has also stated: "In all of Europe there are fewer and fewer children, and the answer of the West is migration," concluding that "We Hungarians have a different way of thinking. Instead of just numbers, we want Hungarian children." ThinkProgress described the comments as pushing a version of the theory. In April 2019, Radio New Zealand published insight that Orban's plans to cut taxes for large Hungarian families could be linked with fears of the Great Replacement.

Republic of Ireland

A 2019 Lidl advertisement that featured a White Irish woman, her Afro-Brazilian partner and their mixed race son was targeted by former journalist Gemma O'Doherty as part of an attempt at a "Great Replacement." After facing online harassment the family decided to leave Ireland. The "Great Replacement" has also been used in Ireland in oppostion to direct provision centres, used to house asylum seekers.

Writing in 2020, Richard Downes said that "Rather than seeing the increase in non-Irish people living and making their lives here as being a normal part of a modern European country, some of the new nationalists see it as a conspiracy to overwhelm Ireland with foreigners. For many of them the conspirators include the Irish government, NGOs, the EU and the UN. They believe that these organisations want to replace Irish people with brown and black people from abroad."

The term "great replacement" was also used when the RTÉ News featured the three first babies born in 2020, born to Polish, Black and Indian mothers; journalist Fergus Finlay saying "I don't care about the vulgar abuse, but I really do believe that these hatemongers should be prosecuted when they incite others to hatred and violence against people whose only crime is their skin colour or religion. I find it hard to understand why the State hasn't acted already against these cruel ideologues who think they can say whatever they like under the banner of free speech. They may be small in number now, and on the surface they may just seem bonkers, but we've been here before. Political movements have been built on hatred of the other, and we know the damage they have caused."

Garda Commissioner (national chief of police) Drew Harris spoke about far right groups in 2020, saying that "Irish groups [believing] in the great replacement theory" had plans "to disrupt key State institutions and infrastructure. This included Dublin Port, high profile shopping areas such as Grafton Street in Dublin, Dáil Éireann and Government departments."

Italy

Meloni accepting the task of forming a new government

The current Italian Prime Minister Giorgia Meloni has endorsed the Great Replacement ideology. Deputy Prime Minister Matteo Salvini of Italy (2018–2019) has repeatedly adopted the theme of the Great Replacement. In May 2016, two years before his election to office, he claimed "ethnic replacement is underway" in Italy in an interview with Sky TG24. Accusing nameless, well-funded organizations for importing workers that he named "farm slaves", he stated that there was a "lucrative attempt at genocide" of Italians.

The Netherlands

In April 2015, writing on the publishing website GeenStijl, scholar of Islam Hans Jansen used Great Replacement rhetoric, suggesting that it was an "undisputed" fact that among the European Union's governing elite there was a common consensus that Europeans were "no good and can be better replaced". In May 2015, Martin Bosma, a Dutch parliament Representative for the Party for Freedom (PVV), released his book Minority in their own land [nl]. Invoking the conspiracy theory, Bosma wrote about a growing 'a new population' of immigrants which lent itself to an apparently 'post-racial Multicultural State of Salvation'.

In March 2017, Thierry Baudet, leader of the right wing Forum for Democracy (FvD) party, promoted the theory after he claimed that the country's so-called elite were deliberately "homeopathically diluting" the Dutch population, in a speech about "national self-hatred". He said there was a plot to racially mix the ethnic Dutch with "all the people of the world", so that there would "never be a Dutchman again".

In January 2018, PVV Representative Martin Bosma endorsed the Great Replacement theory, and one of its key propagators, after meeting with Renaud Camus at a PVV demonstration in Rotterdam and tweeting his support. Filip Dewinter, a leading member of the Flemish secessionist Vlaams Belang party, who had traveled to the Netherlands on the day of the protest to meet with Camus, named him as a "visionary man" to the media.

Party for Freedom politician Geert Wilders of the Netherlands supports the notion of a Great Replacement occurring in Europe. In October 2018, Wilders invoked the conspiracy theory, claiming the Netherlands was "being replaced with mass immigration from non-western Islamic countries" and Rotterdam being "the port of Eurabia". He claimed 77 million, mainly Islamic immigrants would attempt to enter Europe over the course of half a century, and that white Europeans would cease to exist unless they were stopped. In 2019, The New York Times reported how Camus's demographic-based alarmist theories help fuel Wilders and his Party for Freedom's nativist campaigning.

In September 2018, Dutch author Paul Scheffer analyzed the Great Replacement and its political developments, suggesting that Forum for Democracy and Party for Freedom were forming policy regarding the demography of the Netherlands through the lens of the conspiracy theory.

Spain

The far-right party Vox has been described as circulating the theory for its discourse about low natality rates in Spaniards compared to migrants. According to journalist Antonio Maestre of ElDiario.es, such an ideology is shared between Vox and some extreme strains of Catalan nationalism who fear replacement by Spanish-speakers.

United Kingdom

According to November 2018 research from the University of Cambridge, 31% of Brexit voters believe in the conspiracy theory compared to 6% of British people who oppose Brexit.

In July 2019, left-wing English musician and activist Billy Bragg released a public statement which accused fellow singer-songwriter Morrissey of endorsing the theory. Bragg suggested "that Morrissey is helping to spread this idea—which inspired the Christchurch mosque murderer—is beyond doubt".

North America

Canada

YouTuber Lauren Southern of Canada has helped amplify the conspiracy theory. In 2017, Southern dedicated a video to the Great Replacement, gaining over half a million views on her channel, before it was deleted. 2018 mayoral candidate for Toronto Faith Goldy has publicly embraced the replacement theory. In 2019, in the aftermath of the Christchurch mosque shootings in Christchurch, New Zealand, Vice accused Goldy of routinely pushing the same ideas of birthrate declines and the population replacement of whites, found in the gunman's The Great Replacement manifesto. Long-time white nationalist Paul Fromm, when he co-opted the pre-1967 Red Ensign flag of Canada, referred to it as "the flag of the true Canada, the European Canada before the treasonous European replacement schemes brought in by the 1965 immigration policies".

In June 2019, columnist Lindsay Shepherd claimed that "whites are becoming a minority" in the West, describing her assertion as "population replacement". She was criticized by Canadian MP Colin Fraser at a House of Commons justice committee for not denouncing the concept, while Nathaniel Erskine-Smith accused Shepherd of openly embracing the conspiracy theory.

United States

Main article: Great replacement in the United States

The Great replacement in the United States is the American version of a white nationalist far-right conspiracy theory that racial minorities are displacing the traditional white American population and taking control of the nation. Versions of the theory "have become commonplace" in the Republican Party of the United States, and have become a major issue of political debate. It also has stimulated violent responses including mass murders. It resembles the Great Replacement theory promoted in Europe, but has its origins in American nativism around 1900. According to Erika Lee, in 1894 the old stock Yankee upper-class founders of the Immigration Restriction League were, “convinced that Anglo-Saxon traditions, peoples, and culture were being drowned in a flood of racially inferior foreigners from Southern and Eastern Europe.”

Australia

The media in Australia have covered former Senator Fraser Anning of Queensland and his endorsement of the Great Replacement conspiracy theory. In April 2019, Reuters reported how Anning was amplifying replacement theory by suggesting that Muslims would "out-breed us very quickly". In May 2019, Anning alleged that White Australians would "fast become a minority" if they did not defend their "ethno-cultural identity".

Influence on white nationalist terrorism

Implicit call to violence

Camus's use of strong terms like "colonization" and "Occupiers" to label non-European immigrants and their children have been described as implicit calls to violence. Scholars like Jean-Yves Camus have argued that the "Great Replacement" conspiracy theory closely parallels the concept of "remigration", an euphemistic term for the forced deportation of non-white immigrants. "We shall not leave Europe, we shall make Africa leave Europe," Camus wrote in 2019 to define his political agenda for the European parliament elections. He has also used another euphemism, the "Great Repatriation", to refer to remigration.

According to historians Nicolas Bancel and Pascal Blanchard, along with sociologist Ahmed Boubeker, "the announcement of a civil war is implicit in the theory of the 'great replacement' [...] This thesis is extreme—and so simplistic that it can be understood by anyone—because it validates a racial definition of the nation." Sceptical of Camus's description of second or third generation immigrants as being itself a contradiction in terms—"they do not migrate anymore, they are French"—demographer Hervé Le Bras is also critical of their designation as a fifth column in France or an "internal enemy".

Inspired attacks

Fears of the white race's extinction, and replacement theory in particular, have been cited by several accused perpetrators of mass shootings between 2018, 2019 and 2022. While Camus has stated his own philosophy is a nonviolent one, analysts including Heidi Beirich of the Southern Poverty Law Center say the idea of white genocide has "undoubtedly influenced" American white supremacists, potentially leading to violence.

In October 2018, a gunman killed 11 people and injured 6 in an attack on the Tree of Life synagogue in Pittsburgh, Pennsylvania. The gunman believed Jews were deliberately importing non-white immigrants into the United States as part of a conspiracy against the white race.

Brenton Harrison Tarrant, the Australian terrorist responsible for the mass shootings at Al Noor Mosque and Linwood Islamic Centre in Christchurch, New Zealand, on 15 March 2019, that killed 51 people and injured 49, named his manifesto The Great Replacement, a reference to Camus's book. In response, Camus condemned violence while reaffirming his desire for a "counter-revolt" against an increase in nonwhite populations.

In 2019, research by the Institute for Strategic Dialogue showed over 24,000 social media mentions of the Great Replacement in the month before the Christchurch shootings, in comparison to just 3,431 mentions in April 2012. The use of the term spiked in April 2019 after the Christchurch mosque shootings.

Patrick Crusius, the suspect in the 2019 El Paso shooting, posted an online manifesto titled The Inconvenient Truth alluding to the "great replacement" and expressing support for "the Christchurch shooter" minutes before the attack. It spoke of a "Hispanic invasion of Texas" leading to "cultural and ethnic replacement" (alluding to the Reconquista) as justifications for the shooting.

The suspect accused in the 2022 Buffalo shooting listed the Great Replacement in a manifesto he had published prior to the attack. The suspect described himself as a fascist, white supremacist, and antisemite.

Mars sample-return mission

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Mars_sample-return_mission 

 

Mars sample return – artist's concept

A Mars sample-return (MSR) mission is a proposed mission to collect rock and dust samples on Mars and return them to Earth. Such a mission would allow more extensive analysis than that allowed by onboard sensors.

The three most recent concepts are a NASA–ESA proposal, a CNSA proposal, Tianwen-3, and a Roscosmos proposal, Mars-Grunt. Although NASA and ESA's plans to return the samples to Earth are still in the design stage as of 2022, samples have been gathered on Mars by the Perseverance rover.

Risks of cross-contamination of the Earth biosphere from returned Martian samples have been raised, though the risk of this occurring is considered to be extremely low.

Scientific value

Mars meteorites in the Natural History Museum in Vienna

Once returned to Earth, stored samples can be studied with the most sophisticated science instruments available. Thomas Zurbuchen, associate administrator for science at NASA Headquarters in Washington, expect such studies to allow several new discoveries at many fields. Samples may be reanalyzed in the future by instruments that do not yet exist.

In 2006, the Mars Exploration Program Analysis Group identified 55 important investigations related to Mars exploration. In 2008, they concluded that about half of the investigations "could be addressed to one degree or another by MSR", making MSR "the single mission that would make the most progress towards the entire list" of investigations. Moreover, it was reported that a significant fraction of the investigations could not be meaningfully advanced without returned samples.

One source of Mars samples is what are thought to be Martian meteorites, which are rocks ejected from Mars that made their way to Earth. As of April 2019, 266 meteorites had been identified as Martian, out of over 61,000 known meteorites. These meteorites are believed to be from Mars because their elemental and isotopic compositions are similar to rocks and atmospheric gases analyzed on Mars.

History

Artist concept of a Mars sample-return mission, 1993

For at least three decades, scientists have advocated the return of geological samples from Mars. One early concept was the Sample Collection for Investigation of Mars (SCIM) proposal, which involved sending a spacecraft in a grazing pass through Mars's upper atmosphere to collect dust and air samples without landing or orbiting.

The Soviet Union considered a Mars sample-return mission, Mars 5NM, in 1975 but it was cancelled due to the repeated failures of the N1 rocket that would have launched it. Another sample-return mission, Mars 5M (Mars-79), planned for 1979, was cancelled due to complexity and technical problems.

The United States' Mars Exploration Program, formed after Mars Observer's failure in September 1993, supported a Mars sample return. One architecture was proposed by Glenn J. MacPherson in the early 2000s.

In 1996, the possibility of life on Mars was raised when apparent microfossils were thought to have been found in Mars meteorite, ALH84001. This hypothesis was eventually rejected, but led to a renewed interest in a Mars sample return.

As of late 1999, the MSR mission was anticipated to be launched from Earth in 2003 and 2005. Each was to deliver a rover and a Mars ascent vehicle, and a French supplied Mars orbiter with Earth return capability was to be included in 2005. Sample containers orbited by both MAVs were to reach Earth in 2008. This mission concept, considered by NASA's Mars Exploration Program to return samples by 2008, was cancelled following a program review.

In the summer of 2001, the Jet Propulsion Laboratory (JPL) requested mission concepts and proposals from industry-led teams (Boeing, Lockheed Martin, and TRW). The science requirements included at least 500 grams of samples, rover mobility to obtain samples at least 1 kilometer from the landing spot, and drilling to obtain one sample from a depth of 2 meters. That following winter, JPL made similar requests of certain university aerospace engineering departments (MIT and the University of Michigan).

Also in 2001, a separate set of industry studies was done for the Mars ascent vehicle (MAV) due to the uniqueness and key role of the MAV for MSR. Figure 11 in this reference summarized the need for MAV flight testing at a high altitude over Earth, based on Lockheed Martin's analysis that the risk of mission failure is "extremely high" if launch vehicle components are only tested separately.

In 2003, JPL reported that the mission concepts from 2001 had been deemed too costly, which led to the study of a more affordable plan accepted by two groups of scientists, a new MSR Science Steering Group and the Mars Exploration Program Analysis Group (MEPAG). Instead of a rover and deep drilling, a scoop on the lander would dig 20 centimeters deep and place multiple samples together into one container. After five years of technology development, the MAV would be flight-tested twice above Earth before the mission PDR (Preliminary Design Review) in 2009.

In mid-2006, the International Mars Architecture for the Return of Samples (iMARS) Working Group was chartered by the International Mars Exploration Working Group (IMEWG) to outline the scientific and engineering requirements of an internationally sponsored and executed Mars sample-return mission in the 2018–2023 time frame.

In October 2009, NASA and ESA established the Mars Exploration Joint Initiative to proceed with the ExoMars program, whose ultimate aim is "the return of samples from Mars in the 2020s". ExoMars's first mission was planned to launch in 2018 with unspecified missions to return samples in the 2020–2022 time frame. The cancellation of the caching rover MAX-C in 2011, and later NASA withdrawal from ExoMars, due to budget limitations, ended the mission. The pull-out was described as "traumatic" for the science community.

In early 2011, the US National Research Council's Planetary Science Decadal Survey, which laid out mission planning priorities for the period 2013–2022, declared an MSR campaign its highest priority Flagship Mission for that period. In particular, it endorsed the proposed Mars Astrobiology Explorer-Cacher (MAX-C) mission in a "descoped" (less ambitious) form. This mission plan was officially cancelled in April 2011.

In September 2012, NASA announced its intention to further study several strategies of bringing a sample of Mars to Earth – including a multiple launch scenario, a single-launch scenario, and a multiple-rover scenario – for a mission beginning as early as 2018. A "fetch rover" would retrieve the sample caches and deliver them to a Mars ascent vehicle (MAV). In July 2018, NASA contracted Airbus to produce a "fetch rover" concept.

In April 2018, a letter of intent was signed by NASA and ESA that may provide a basis for a Mars sample-return mission. In July 2019, a mission architecture was proposed. In April 2020, an updated version of the mission was presented.

A key mission requirement for the Mars 2020 Perseverance rover mission was that it help prepare for MSR. The rover landed on 18 February 2021 in Jezero Crater to collect samples and store them in 43 cylindrical tubes for later retrieval.

Mars 2020 mission

Mapping Perseverance's samples collected to date

 

Facsimiles of Perseverance's sample tubes at JPL in Southern California

 

In support of the Mars sample-return mission, rock, regolith (Martian 'soil'), and atmosphere samples are being cached by Perseverance. Currently, out of 43 sample tubes, rock sample tubes cached: 14, atmosphere sample tubes cached: 1, witness tubes cached: 3, tubes due to be cached: 25. Before launch, 5 of the 43 tubes were designated “witness tubes” and filled with materials that would capture particulates in the ambient environment of Mars.

The Mars 2020 mission landed the Perseverance rover in Jezero crater in February 2021. It collected multiple samples and packed them into cylinders for later return. Jezero appears to be an ancient lakebed, suitable for ground sampling.

In the beginning of August 2021, Perseverance made its first attempt to collect a ground sample by drilling out a finger-size core of Martian rock. This attempt did not succeed. A drill hole was produced, as indicated by instrument readings, and documented by a photograph of the drill hole. However, the sample container turned out to be empty, indicating that the rock sampled was not robust enough to produce a solid core.

A second target rock judged to have a better chance to yield a sufficiently robust sample was sampled at the end of August and the beginning of September 2021. After abrading the rock, cleaning away dust by puffs of pressurized nitrogen, and inspecting the resulting rock surface, a hole was drilled on September 1. A rock sample appeared to be in the tube, but it was not immediately placed in a container. A new procedure of inspecting the tube optically was performed. On September 6, the process was completed and the first sample placed in a container.

NASA–ESA concept

Mars Sample return mission logo

The NASA-ESA plan is to return samples using three missions: a sample collection mission (Perseverance), a sample retrieval mission (Sample Retrieval Lander + Mars ascent vehicle + Sample Transfer arm + 2 Ingenuity class helicopters), and a return mission (Earth Return Orbiter). The mission hopes to resolve the question of whether Mars once harbored life.

Sample collection

The Mars 2020 mission landed the Perseverance rover, which is storing samples to be returned to Earth later. After consideration, it was decided that given Perseverance's expected longevity, it will be the primary means of transporting samples to Sample Retrieval Lander (SRL).

Mars 2020 Perseverance Rover

Sample retrieval

Mars Sample Return Program
(Artwork; 27 July 2022)

The sample retrieval mission involves launching a sample return lander in 2028 with the Mars Ascent Vehicle and two Ingenuity class sample recovery helicopters, both of which will be collecting the samples with a tiny robotic arm as a backup for Perseverance. The rover and helicopters will transport the samples to the SRL lander. SRL's robotic arm will be used to extract the samples and load them into the Sample Return Capsule in the Ascent Vehicle. It is planned to land near the Octavia E. Butler Landing site in 2029.

Mars Ascent Vehicle (MAV)

A mock-up of Mars Ascent Vehicle on display stand

 

VECTOR release sequence

MAV is a 3-meter long, two-stage, solid-fueled rocket that will deliver the collected samples from the surface of Mars to the Earth Return Orbiter. Early in 2022, Lockheed Martin was awarded a contract to partner with NASA's Marshall Space Flight Center in developing the MAV. It is planned to be catapulted into the air just before it ignites, at a rate of 16 feet (5 meters) per second, to remove the odds of wrong liftoff like slipping or tilting of SRL under rocket's shear weight and exhaust at liftoff. This Vertically Ejected Controlled Tip-off Release (VECTOR) system adds a slight rotation during launch, pitching the rocket up and away from the surface. MAV would enter a 380 km orbit. It will remain stowed inside a cylinder on the SRL and will have a thermal protective coating. The rocket's first stage would be run by a single updated STAR-20 engine burning for 70 seconds, while the second stage would have a single updated STAR-15 engine burning for another 27 seconds. They would be separated by a coast phase, after which the sample container would be released in orbit. As of early 2022, the second stage is planned to be spin-stabilized to save weight in lieu of active guidance, while the Mars samples will result in an unknown payload mass distribution.

MAV is scheduled to be launched in 2028 on board the SRL lander.

Sample return

Earth Return Orbiter (ERO)

ERO is an ESA-developed spacecraft. It includes the NASA-built Capture and Containment and Return System to rendezvous with the samples delivered by MAV in low Mars orbit (LMO).

ERO is scheduled to launch on an Ariane 64 rocket in 2027 and arrive at Mars in 2028, using ion propulsion and a separate propulsion element to gradually reach the proper orbit and then rendezvous with the orbiting sample. The MAV's 2nd stage will have a radio beacon that will give controllers the information they need to get the ESA Earth Return Orbiter close enough to the Orbiting Sample to see it through reflective light and capture it for return to earth. The orbiter will retrieve and seal the canisters in orbit and use a NASA-built robotic arm to place the sealed container into an Earth-entry capsule. It will raise its orbit, release the propulsion element, and return to Earth during the 2033 Mars-to-Earth transfer window.

Earth Entry Vehicle (EEV)

The Capture/Containment and Return System (CCRS) would stow the sample in the EEV. EEV would return to Earth and land passively, without a parachute. The desert sand at the Utah Test and Training Range and shock absorbing materials in the vehicle were planned to protect the samples from impact forces. EEV is scheduled to land on Earth in 2033.

Components of the Sample Return Landers

Interior design of MAV, First Extraterrestrial Staging Rocket

 

MAV exterior design

 

MAV flight plan

 

Mars Sample Return 2020-2033 Timeline

 

Artist's concept of Mars sample return orbiter

cross section of the Earth return orbiter

 

Earth Return Orbiter

 

Capture and containment system

Additional plans

China

China has announced plans for a Mars sample-return mission to be called Tianwen-3. The mission would launch in late 2028, with a lander and ascent vehicle on a Long March 5 and an orbiter and return module launched separately on a Long March 3B. Samples would be returned to Earth in July 2031.

A previous plan would have used a large spacecraft that could carry out all mission phases, including sample collection, ascent, orbital rendezvous, and return flight. This would have required the super-heavy-lift Long March 9 launch vehicle. Another plan involved using Tianwen-1 to cache the samples for retrieval.

France

France has worked towards a sample return for many years. This included concepts of an extraterrestrial sample curation facility for returned samples, and numerous proposals. They worked on the development of a Mars sample-return orbiter, which would capture and return the samples as part of a joint mission with other countries.

Japan

On 9 June 2015, the Japanese Aerospace Exploration Agency (JAXA) unveiled a plan named Martian Moons Exploration (MMX) to retrieve samples from Phobos or Deimos. Phobos's orbit is closer to Mars and its surface may have captured particles blasted from Mars. The launch from Earth is planned for September 2024, with a return to Earth in 2029. Japan has also shown interest in participating in an international Mars sample-return mission.

Russia

Main article: Mars-Grunt

A Russian Mars sample-return mission concept is Mars-Grunt. It adopted Fobos-Grunt design heritage. 2011 plans envisioned a two-stage architecture with an orbiter and a lander (but no roving capability), with samples gathered from around the lander by a robotic arm.

Back contamination

Further information: Extraterrestrial sample curation and Planetary protection

Whether life forms exist on Mars is unresolved. Thus, MSR could potentially transfer viable organisms to Earth, resulting in back contamination — the introduction of extraterrestrial organisms into Earth's biosphere. The scientific consensus is that the potential for large-scale effects, either through pathogenesis or ecological disruption, is small. Returned samples would be treated as potentially biohazardous until scientists decide the samples are safe. The goal is that the probability of release of a Mars particle is less than one in a million.

The proposed NASA Mars sample-return mission will not be approved by NASA until the National Environmental Policy Act (NEPA) process has been completed. Furthermore, under the terms of Article VII of the Outer Space Treaty and other legal frameworks, were a release of organisms to occur, the releasing nation(s) would be liable for any resultant damages.

The sample-return mission would be tasked with preventing contact between the Martian environment and the exterior of the sample containers.

In order to eliminate the risk of parachute failure, the current plan is to use the thermal protection system to cushion the capsule upon impact (at terminal velocity). The sample container would be designed to withstand the force of impact. To receive the returned samples, NASA proposed a custom Biosafety Level 4 containment facility, the Mars Sample-Return Receiving facility (MSRRF).

Other scientists and engineers, notably Robert Zubrin of the Mars Society, argued in the Journal of Cosmology that contamination risk is functionally zero leaving little need to worry. They cite, among other things, lack of any known incident although trillions of kilograms of material have been exchanged between Mars and Earth via meteorite impacts.

The International Committee Against Mars Sample Return (ICAMSR) is an advocacy group led by Barry DiGregorio, that campaigns against a Mars sample-return mission. While ICAMSR acknowledges a low probability for biohazards, it considers the proposed containment measures to be unsafe. ICAMSR advocates more in situ studies on Mars, and preliminary biohazard testing at the International Space Station before the samples are brought to Earth. DiGregorio accepts the conspiracy theory of a NASA coverup regarding the discovery of microbial life by the 1976 Viking landers. DiGregorio also supports a view that several pathogens – such as common viruses – originate in space and probably caused some mass extinctions and pandemics. These claims connecting terrestrial disease and extraterrestrial pathogens have been rejected by the scientific community.

Isotope geochemistry

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Isotope_geochemistry 

Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements. Variations in isotopic abundance are measured by isotope ratio mass spectrometry, and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between them.

Stable isotope geochemistry is largely concerned with isotopic variations arising from mass-dependent isotope fractionation, whereas radiogenic isotope geochemistry is concerned with the products of natural radioactivity.

Stable isotope geochemistry

For most stable isotopes, the magnitude of fractionation from kinetic and equilibrium fractionation is very small; for this reason, enrichments are typically reported in "per mil" (‰, parts per thousand). These enrichments (δ) represent the ratio of heavy isotope to light isotope in the sample over the ratio of a standard. That is,

${\displaystyle \delta {}^{13}\text{C}=\left(\frac{{\left(\frac{{}^{13}\text{C}}{{}^{12}\text{C}}\right)}_{sample}}{{\left(\frac{{}^{13}\text{C}}{{}^{12}\text{C}}\right)}_{standard}}-1\right)\times 1000}$ ‰

Hydrogen

Main article: Hydrogen isotope biogeochemistry

Carbon

Main article: δ13C

Carbon has two stable isotopes, ¹²C and ¹³C, and one radioactive isotope, ¹⁴C.

The stable carbon isotope ratio, δ¹³C, is measured against Vienna Pee Dee Belemnite (VPDB). The stable carbon isotopes are fractionated primarily by photosynthesis (Faure, 2004). The ¹³C/¹²C ratio is also an indicator of paleoclimate: a change in the ratio in the remains of plants indicates a change in the amount of photosynthetic activity, and thus in how favorable the environment was for the plants. During photosynthesis, organisms using the C₃ pathway show different enrichments compared to those using the C₄ pathway, allowing scientists not only to distinguish organic matter from abiotic carbon, but also what type of photosynthetic pathway the organic matter was using. Occasional spikes in the global ¹³C/¹²C ratio have also been useful as stratigraphic markers for chemostratigraphy, especially during the Paleozoic.

The ¹⁴C ratio has been used to track ocean circulation, among other things.

Nitrogen

Nitrogen has two stable isotopes, ¹⁴N and ¹⁵N. The ratio between these is measured relative to nitrogen in ambient air. Nitrogen ratios are frequently linked to agricultural activities. Nitrogen isotope data has also been used to measure the amount of exchange of air between the stratosphere and troposphere using data from the greenhouse gas N₂O.

Oxygen

Oxygen has three stable isotopes, ¹⁶O, ¹⁷O, and ¹⁸O. Oxygen ratios are measured relative to Vienna Standard Mean Ocean Water (VSMOW) or Vienna Pee Dee Belemnite (VPDB). Variations in oxygen isotope ratios are used to track both water movement, paleoclimate, and atmospheric gases such as ozone and carbon dioxide. Typically, the VPDB oxygen reference is used for paleoclimate, while VSMOW is used for most other applications. Oxygen isotopes appear in anomalous ratios in atmospheric ozone, resulting from mass-independent fractionation. Isotope ratios in fossilized foraminifera have been used to deduce the temperature of ancient seas.

Sulfur

Sulfur has four stable isotopes, with the following abundances: ³²S (0.9502), ³³S (0.0075), ³⁴S (0.0421) and ³⁶S (0.0002). These abundances are compared to those found in Cañon Diablo troilite. Variations in sulfur isotope ratios are used to study the origin of sulfur in an orebody and the temperature of formation of sulfur–bearing minerals as well as a biosignature that can reveal presence of sulfate reducing microbes.

Radiogenic isotope geochemistry

Main article: Radiometric dating

Radiogenic isotopes provide powerful tracers for studying the ages and origins of Earth systems. They are particularly useful to understand mixing processes between different components, because (heavy) radiogenic isotope ratios are not usually fractionated by chemical processes.

Radiogenic isotope tracers are most powerful when used together with other tracers: The more tracers used, the more control on mixing processes. An example of this application is to the evolution of the Earth's crust and Earth's mantle through geological time.

Lead–lead isotope geochemistry

Main article: Lead–lead dating

Lead has four stable isotopes: ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb.

Lead is created in the Earth via decay of actinide elements, primarily uranium and thorium.

Lead isotope geochemistry is useful for providing isotopic dates on a variety of materials. Because the lead isotopes are created by decay of different transuranic elements, the ratios of the four lead isotopes to one another can be very useful in tracking the source of melts in igneous rocks, the source of sediments and even the origin of people via isotopic fingerprinting of their teeth, skin and bones.

It has been used to date ice cores from the Arctic shelf, and provides information on the source of atmospheric lead pollution.

Lead–lead isotopes has been successfully used in forensic science to fingerprint bullets, because each batch of ammunition has its own peculiar ²⁰⁴Pb/²⁰⁶Pb vs ²⁰⁷Pb/²⁰⁸Pb ratio.

Samarium–neodymium

Main article: Samarium–neodymium dating

Samarium–neodymium is an isotope system which can be utilised to provide a date as well as isotopic fingerprints of geological materials, and various other materials including archaeological finds (pots, ceramics).

¹⁴⁷Sm decays to produce ¹⁴³Nd with a half life of 1.06x10¹¹ years.

Dating is achieved usually by trying to produce an isochron of several minerals within a rock specimen. The initial ¹⁴³Nd/¹⁴⁴Nd ratio is determined.

This initial ratio is modelled relative to CHUR - the Chondritic Uniform Reservoir - which is an approximation of the chondritic material which formed the solar system. CHUR was determined by analysing chondrite and achondrite meteorites.

The difference in the ratio of the sample relative to CHUR can give information on a model age of extraction from the mantle (for which an assumed evolution has been calculated relative to CHUR) and to whether this was extracted from a granitic source (depleted in radiogenic Nd), the mantle, or an enriched source.

Rhenium–osmium

Main article: Rhenium–osmium dating

Rhenium and osmium are siderophile elements which are present at very low abundances in the crust. Rhenium undergoes radioactive decay to produce osmium. The ratio of non-radiogenic osmium to radiogenic osmium throughout time varies.

Rhenium prefers to enter sulfides more readily than osmium. Hence, during melting of the mantle, rhenium is stripped out, and prevents the osmium–osmium ratio from changing appreciably. This locks in an initial osmium ratio of the sample at the time of the melting event. Osmium–osmium initial ratios are used to determine the source characteristic and age of mantle melting events.

Noble gas isotopes

Natural isotopic variations amongst the noble gases result from both radiogenic and nucleogenic production processes. Because of their unique properties, it is useful to distinguish them from the conventional radiogenic isotope systems described above.

Helium-3

Helium-3 was trapped in the planet when it formed. Some ³He is being added by meteoric dust, primarily collecting on the bottom of oceans (although due to subduction, all oceanic tectonic plates are younger than continental plates). However, ³He will be degassed from oceanic sediment during subduction, so cosmogenic ³He is not affecting the concentration or noble gas ratios of the mantle.

Helium-3 is created by cosmic ray bombardment, and by lithium spallation reactions which generally occur in the crust. Lithium spallation is the process by which a high-energy neutron bombards a lithium atom, creating a ³He and a ⁴He ion. This requires significant lithium to adversely affect the ³He/⁴He ratio.

All degassed helium is lost to space eventually, due to the average speed of helium exceeding the escape velocity for the Earth. Thus, it is assumed the helium content and ratios of Earth's atmosphere have remained essentially stable.

It has been observed that ³He is present in volcano emissions and oceanic ridge samples. How ³He is stored in the planet is under investigation, but it is associated with the mantle and is used as a marker of material of deep origin.

Due to similarities in helium and carbon in magma chemistry, outgassing of helium requires the loss of volatile components (water, carbon dioxide) from the mantle, which happens at depths of less than 60 km. However, ³He is transported to the surface primarily trapped in the crystal lattice of minerals within fluid inclusions.

Helium-4 is created by radiogenic production (by decay of uranium/thorium-series elements). The continental crust has become enriched with those elements relative to the mantle and thus more He⁴ is produced in the crust than in the mantle.

The ratio (R) of ³He to ⁴He is often used to represent ³He content. R usually is given as a multiple of the present atmospheric ratio (Ra).

Common values for R/Ra:

• Old continental crust: less than 1
• mid-ocean ridge basalt (MORB): 7 to 9
• Spreading ridge rocks: 9.1 plus or minus 3.6
• Hotspot rocks: 5 to 42
• Ocean and terrestrial water: 1
• Sedimentary formation water: less than 1
• Thermal spring water: 3 to 11

³He/⁴He isotope chemistry is being used to date groundwaters, estimate groundwater flow rates, track water pollution, and provide insights into hydrothermal processes, igneous geology and ore genesis.

• (U-Th)/He dating of apatite as a thermal history tool
• USGS: Helium Discharge at Mammoth Mountain Fumarole (MMF)

Isotopes in actinide decay chains

Isotopes in the decay chains of actinides are unique amongst radiogenic isotopes because they are both radiogenic and radioactive. Because their abundances are normally quoted as activity ratios rather than atomic ratios, they are best considered separately from the other radiogenic isotope systems.

Protactinium/Thorium – ²³¹Pa / ²³⁰Th

Uranium is well mixed in the ocean, and its decay produces ²³¹Pa and ²³⁰Th at a constant activity ratio (0.093). The decay products are rapidly removed by adsorption on settling particles, but not at equal rates. ²³¹Pa has a residence equivalent to the residence time of deep water in the Atlantic basin (around 1000 yrs) but ²³⁰Th is removed more rapidly (centuries). Thermohaline circulation effectively exports ²³¹Pa from the Atlantic into the Southern Ocean, while most of the ²³⁰Th remains in Atlantic sediments. As a result, there is a relationship between ²³¹Pa/²³⁰Th in Atlantic sediments and the rate of overturning: faster overturning produces lower sediment ²³¹Pa/²³⁰Th ratio, while slower overturning increases this ratio. The combination of δ¹³C and ²³¹Pa/²³⁰Th can therefore provide a more complete insight into past circulation changes.

Anthropogenic isotopes

Tritium/helium-3

Tritium was released to the atmosphere during atmospheric testing of nuclear bombs. Radioactive decay of tritium produces the noble gas helium-3. Comparing the ratio of tritium to helium-3 (³H/³He) allows estimation of the age of recent ground waters. A small amount of Tritium is also produced naturally by cosmic ray spallation and spontaneous ternary fission in natural uranium and thorium, but due to the relatively short half-life of Tritium and the relatively small quantities (compared to those from humandmade sources) those sources of Tritium usually play only a secondary role in the analysis of groundwater.

• USGS Tritium/Helium-3 Dating
• Hydrologic Isotope Tracers - Helium