{"id":312848,"date":"2021-02-15T05:00:54","date_gmt":"2021-02-15T10:00:54","guid":{"rendered":"https:\/\/news.harvard.edu\/gazette\/?p=312848"},"modified":"2024-01-10T17:58:15","modified_gmt":"2024-01-10T22:58:15","slug":"new-theory-behind-asteroid-that-killed-the-dinosaurs","status":"publish","type":"post","link":"https:\/\/news.harvard.edu\/gazette\/story\/2021\/02\/new-theory-behind-asteroid-that-killed-the-dinosaurs\/","title":{"rendered":"The cataclysm that killed the dinosaurs"},"content":{"rendered":"<header\n\tclass=\"wp-block-harvard-gazette-article-header alignfull article-header is-style-full-width-text-below centered-image\"\n\tstyle=\" \"\n>\n\t\n<figure class=\"wp-block-video\">\n<span class=\"embed-youtube\" style=\"text-align:center; display: block;\"><iframe loading=\"lazy\" class=\"youtube-player\" width=\"640\" height=\"360\" src=\"https:\/\/www.youtube.com\/embed\/ExNL1HJvP1E?version=3&#038;rel=1&#038;showsearch=0&#038;showinfo=1&#038;iv_load_policy=1&#038;fs=1&#038;hl=en-US&#038;autohide=2&#038;wmode=transparent\" allowfullscreen=\"true\" style=\"border:0;\" sandbox=\"allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox\"><\/iframe><\/span>\n<figcaption class=\"wp-element-caption\"><p class=\"wp-element-caption--credit\">Video: Kai-Jae Wang\/Harvard Staff<\/p><\/figcaption><\/figure>\n\n\t<div class=\"article-header__content\">\n\t\t\t<a\n\t\t\tclass=\"article-header__category\"\n\t\t\thref=\"https:\/\/news.harvard.edu\/gazette\/section\/science-technology\/\"\n\t\t>\n\t\t\tScience &amp; Tech\t\t<\/a>\n\t\t\n\t\t<h1 class=\"article-header__title wp-block-heading \">\n\t\tThe cataclysm that killed the dinosaurs\t<\/h1>\n\n\t\n\t\t\t<\/div>\n\t\t\n\t<div class=\"article-header__meta\">\n\t\t<div class=\"wp-block-post-author\">\n\t\t\t<address class=\"wp-block-post-author__content\">\n\t\t\t\t\t<p class=\"author wp-block-post-author__name\">\n\t\tJuan Siliezar\t<\/p>\n\t\t\t<p class=\"wp-block-post-author__byline\">\n\t\t\tHarvard Staff Writer\t\t<\/p>\n\t\t\t\t\t<\/address>\n\t\t<\/div>\n\n\t\t<time class=\"article-header__date\" datetime=\"2021-02-15\">\n\t\t\tFebruary 15, 2021\t\t<\/time>\n\n\t\t<span class=\"article-header__reading-time\">\n\t\t\t5 min read\t\t<\/span>\n\t<\/div>\n\n\t\n\t\t\t<h2 class=\"article-header__subheading wp-block-heading\">\n\t\t\tNew theory explains possible origin of plummeting Chicxulub impactor that struck off Mexico\t\t<\/h2>\n\t\t\n<\/header>\n\n\n\n<div class=\"wp-block-group alignwide has-global-padding is-content-justification-center is-layout-constrained wp-block-group-is-layout-constrained\">\n<p>It was tens of miles wide and forever changed history when it crashed into Earth about 66 million years ago.<\/p>\n\n\n\n<p>The Chicxulub impactor, as it\u2019s known, was a plummeting asteroid or comet that left behind a crater off the coast of Mexico that spans 93 miles and goes 12 miles deep. Its devastating impact brought the reign of the dinosaurs to an abrupt and calamitous end, scientists say, by triggering their sudden mass extinction, along with the end of almost three-quarters of the plant and animal species then living on Earth.<\/p>\n\n\n\n<p>The enduring puzzle has always been where the asteroid or comet originated, and how it came to strike the Earth. And now a pair of Harvard researchers believe they have the answer.<\/p>\n\n\n\n<p>In a <a href=\"http:\/\/www.nature.com\/articles\/s41598-021-82320-2\">study<\/a> published in Scientific Reports, <a href=\"https:\/\/astronomy.fas.harvard.edu\/people\/avi-loeb\">Avi Loeb<\/a>, Frank B. Baird Jr. Professor of Science at Harvard, and <a href=\"https:\/\/scholar.harvard.edu\/siraj\">Amir Siraj<\/a> \u201921, an astrophysics concentrator, put forth a new theory that could explain the origin and journey of this catastrophic object and others like it.<\/p>\n\n\n\n<p>Using statistical analysis and gravitational simulations, Loeb and Siraj say that a significant fraction of a type of comet originating from the Oort cloud, a sphere of debris at the edge of the solar system, was bumped off-course by Jupiter\u2019s gravitational field during its orbit and sent close to the sun, whose tidal force broke apart pieces of the rock. That increases the rate of comets like Chicxulub (pronounced Chicks-uh-lub) because these fragments cross the Earth\u2019s orbit and hit the planet once every 250 to 730 million years or so.<\/p>\n\n\n\n<p>\u201cBasically, Jupiter acts as a kind of pinball machine,\u201d said Siraj, who is also co-president of <a href=\"http:\/\/www.hcs.harvard.edu\/~seds\/\">Harvard Students for the Exploration and Development of Space<\/a> and is pursuing a master\u2019s degree at the New England Conservatory of Music. \u201cJupiter kicks these incoming long-period comets into orbits that bring them very close to the sun.\u201d<\/p>\n\n\n\n<p>It\u2019s because of this that long-period comets, which take more than 200 years to orbit the sun, are called sun grazers, he said.<\/p>\n\n\n\n<p>\u201cWhen you have these sun grazers, it\u2019s not so much the melting that goes on, which is a pretty small fraction relative to the total mass, but the comet is so close to the sun that the part that\u2019s closer to the sun feels a stronger gravitational pull than the part that is farther from the sun, causing a tidal force\u201d he said. \u201cYou get what\u2019s called a tidal disruption event and so these large comets that come really close to the sun break up into smaller comets. And basically, on their way out, there\u2019s a statistical chance that these smaller comets hit the Earth.\u201d<\/p>\n\n\n\n<p>The calculations from Loeb and Siraj\u2019s theory increase the chances of long-period comets impacting Earth by a factor of about 10, and show that about 20 percent of long-period comets become sun grazers. That finding falls in line with research from other astronomers.<\/p>\n\n\n\n<p>The pair claim that their new rate of impact is consistent with the age of Chicxulub, providing a satisfactory explanation for its origin and other impactors like it.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"2500\" height=\"1667\" src=\"https:\/\/news.harvard.edu\/gazette\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg\" alt=\"Avi Loeb.\" class=\"wp-image-314983\" srcset=\"https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg 2500w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=150,100 150w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=300,200 300w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=768,512 768w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=1024,683 1024w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=1536,1024 1536w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=2048,1366 2048w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=48,32 48w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=96,64 96w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=1488,992 1488w, https:\/\/news.harvard.edu\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg?resize=1680,1120 1680w\" sizes=\"auto, (max-width: 2500px) 100vw, 2500px\" \/><figcaption class=\"wp-element-caption\"><p class=\"wp-element-caption--caption\">Understanding Chicxulub impactor is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again, contends Avi Loeb, Frank B. Baird Jr. Professor of Science at Harvard. Kris Snibbe\/Harvard file photo\t\t\t<\/p><p class=\"wp-element-caption--credit\">Harvard University<\/p><\/figcaption><\/figure>\n\n\n\n<p>\u201cOur paper provides a basis for explaining the occurrence of this event,\u201d Loeb said. \u201cWe are suggesting that, in fact, if you break up an object as it comes close to the sun, it could give rise to the appropriate event rate and also the kind of impact that killed the dinosaurs.\u201d<\/p>\n\n\n\n<p>Loeb and Siraj\u2019s hypothesis might also explain the makeup of many of these impactors.<\/p>\n\n\n\n<p>\u201cOur hypothesis predicts that other Chicxulub-size craters on Earth are more likely to correspond to an impactor with a primitive (carbonaceous chondrite) composition than expected from the conventional main-belt asteroids,\u201d the researchers wrote in the paper.<\/p>\n\n\n\n<p>This is important because a popular theory on the origin of Chicxulub claims the impactor is a fragment of a much larger asteroid that came from the main belt, which is an asteroid population between the orbit of Jupiter and Mars. Only about a tenth of all main-belt asteroids have a composition of carbonaceous chondrite, while it\u2019s assumed most long-period comets have it. Evidence found at the Chicxulub crater and other similar craters that suggests they had carbonaceous chondrite.<\/p>\n\n\n\n<p>This includes an object that hit about 2 billion years ago and left the Vredefort crater in South Africa, which is the largest confirmed crater in Earth\u2019s history, and the impactor that left the Zhamanshin crater in Kazakhstan, which is the largest confirmed crater within the last million years.<\/p>\n\n\n\n<p>The researchers say that composition evidence supports their model and that the years the objects hit support both their calculations on impact rates of Chicxulub-sized tidally disrupted comets and for smaller ones like the impactor that made the Zhamanshin crater. If produced the same way, they say those would strike Earth once every 250,000 to 730,000 years.<\/p>\n\n\n\n<p>Aside from composition of comets, the new Vera Rubin Observatory in Chile may be able to see the tidal disruption of long-period comets after it becomes operational next year.<\/p>\n\n\n\n<p>\u201cWe should see smaller fragments coming to Earth more frequently from the Oort cloud,\u201d Loeb said. \u201cI hope that we can test the theory by having more data on long-period comets, get better statistics, and perhaps see evidence for some fragments.\u201d<\/p>\n\n\n\n<p>Loeb said understanding this is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again.<\/p>\n\n\n\n<p>\u201cIt must have been an amazing sight, but we don\u2019t want to see that side,\u201d he said.<\/p>\n\n\n\n<p><em>This work was partially supported by the <\/em><a href=\"https:\/\/origins.harvard.edu\/\"><em>Harvard Origins of Life Initiative<\/em><\/a><em> and the Breakthrough Prize Foundation.<\/em><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>New theory explains origin of comet that killed the dinosaurs<\/p>\n","protected":false},"author":131912115,"featured_media":315067,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"gz_ga_pageviews":286,"gz_ga_lastupdated":"2025-10-04 21:42","document_color_palette":"blue","author":"Juan Siliezar","affiliation":"Harvard Staff Writer","_category_override":"","_yoast_wpseo_primary_category":"1387","_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1387],"tags":[46668,5159,46996,46995,46997,46994,13050,15423,41823,30702],"gazette-formats":[],"series":[],"class_list":["post-312848","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science-technology","tag-amir-siraj","tag-avi-loeb","tag-chicxulub-crater","tag-chicxulub-impactor","tag-cretaceous-paleogene-extinction-event","tag-dinosaur-extinction","tag-fas","tag-harvard-astronomy-department","tag-juan-siliezar","tag-scientific-reports"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v23.0 (Yoast SEO v27.1.1) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>New theory behind Chicxulub impactor that killed the dinosaurs &#8212; 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Tech\t\t<\/a>\n\t\t\n\t\t<h1 class=\"article-header__title wp-block-heading \">\n\t\tThe cataclysm that killed the dinosaurs\t<\/h1>\n\n\t\n\t\t\t<\/div>\n\t\t\n\t<div class=\"article-header__meta\">\n\t\t<div class=\"wp-block-post-author\">\n\t\t\t<address class=\"wp-block-post-author__content\">\n\t\t\t\t\t<p class=\"author wp-block-post-author__name\">\n\t\tJuan Siliezar\t<\/p>\n\t\t\t<p class=\"wp-block-post-author__byline\">\n\t\t\tHarvard Staff Writer\t\t<\/p>\n\t\t\t\t\t<\/address>\n\t\t<\/div>\n\n\t\t<time class=\"article-header__date\" datetime=\"2021-02-15\">\n\t\t\tFebruary 15, 2021\t\t<\/time>\n\n\t\t<span class=\"article-header__reading-time\">\n\t\t\t5 min read\t\t<\/span>\n\t<\/div>\n\n\t\n\t\t\t<h2 class=\"article-header__subheading wp-block-heading\">\n\t\t\tNew theory explains possible origin of plummeting Chicxulub impactor that struck off Mexico\t\t<\/h2>\n\t\t\n<\/header>\n"},"2":{"blockName":"core\/group","attrs":{"templateLock":false,"metadata":{"name":"Article content"},"align":"wide","layout":{"type":"constrained","justifyContent":"center"},"tagName":"div","lock":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","ariaLabel":"","anchor":""},"innerBlocks":[{"blockName":"core\/paragraph","attrs":{"align":"","content":"It was tens of miles wide and forever changed history when it crashed into Earth about 66 million years ago.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>It was tens of miles wide and forever changed history when it crashed into Earth about 66 million years ago.<\/p>\n","innerContent":["\n<p>It was tens of miles wide and forever changed history when it crashed into Earth about 66 million years ago.<\/p>\n"],"rendered":"\n<p>It was tens of miles wide and forever changed history when it crashed into Earth about 66 million years ago.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"The Chicxulub impactor, as it\u2019s known, was a plummeting asteroid or comet that left behind a crater off the coast of Mexico that spans 93 miles and goes 12 miles deep. Its devastating impact brought the reign of the dinosaurs to an abrupt and calamitous end, scientists say, by triggering their sudden mass extinction, along with the end of almost three-quarters of the plant and animal species then living on Earth.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>The Chicxulub impactor, as it\u2019s known, was a plummeting asteroid or comet that left behind a crater off the coast of Mexico that spans 93 miles and goes 12 miles deep. Its devastating impact brought the reign of the dinosaurs to an abrupt and calamitous end, scientists say, by triggering their sudden mass extinction, along with the end of almost three-quarters of the plant and animal species then living on Earth.<\/p>\n","innerContent":["\n<p>The Chicxulub impactor, as it\u2019s known, was a plummeting asteroid or comet that left behind a crater off the coast of Mexico that spans 93 miles and goes 12 miles deep. Its devastating impact brought the reign of the dinosaurs to an abrupt and calamitous end, scientists say, by triggering their sudden mass extinction, along with the end of almost three-quarters of the plant and animal species then living on Earth.<\/p>\n"],"rendered":"\n<p>The Chicxulub impactor, as it\u2019s known, was a plummeting asteroid or comet that left behind a crater off the coast of Mexico that spans 93 miles and goes 12 miles deep. Its devastating impact brought the reign of the dinosaurs to an abrupt and calamitous end, scientists say, by triggering their sudden mass extinction, along with the end of almost three-quarters of the plant and animal species then living on Earth.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"The enduring puzzle has always been where the asteroid or comet originated, and how it came to strike the Earth. And now a pair of Harvard researchers believe they have the answer.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>The enduring puzzle has always been where the asteroid or comet originated, and how it came to strike the Earth. And now a pair of Harvard researchers believe they have the answer.<\/p>\n","innerContent":["\n<p>The enduring puzzle has always been where the asteroid or comet originated, and how it came to strike the Earth. And now a pair of Harvard researchers believe they have the answer.<\/p>\n"],"rendered":"\n<p>The enduring puzzle has always been where the asteroid or comet originated, and how it came to strike the Earth. And now a pair of Harvard researchers believe they have the answer.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"In a <a href=\"http:\/\/www.nature.com\/articles\/s41598-021-82320-2\">study<\/a> published in Scientific Reports, <a href=\"https:\/\/astronomy.fas.harvard.edu\/people\/avi-loeb\">Avi Loeb<\/a>, Frank B. Baird Jr. Professor of Science at Harvard, and <a href=\"https:\/\/scholar.harvard.edu\/siraj\">Amir Siraj<\/a> \u201921, an astrophysics concentrator, put forth a new theory that could explain the origin and journey of this catastrophic object and others like it.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>In a <a href=\"http:\/\/www.nature.com\/articles\/s41598-021-82320-2\">study<\/a> published in Scientific Reports, <a href=\"https:\/\/astronomy.fas.harvard.edu\/people\/avi-loeb\">Avi Loeb<\/a>, Frank B. Baird Jr. Professor of Science at Harvard, and <a href=\"https:\/\/scholar.harvard.edu\/siraj\">Amir Siraj<\/a> \u201921, an astrophysics concentrator, put forth a new theory that could explain the origin and journey of this catastrophic object and others like it.<\/p>\n","innerContent":["\n<p>In a <a href=\"http:\/\/www.nature.com\/articles\/s41598-021-82320-2\">study<\/a> published in Scientific Reports, <a href=\"https:\/\/astronomy.fas.harvard.edu\/people\/avi-loeb\">Avi Loeb<\/a>, Frank B. Baird Jr. Professor of Science at Harvard, and <a href=\"https:\/\/scholar.harvard.edu\/siraj\">Amir Siraj<\/a> \u201921, an astrophysics concentrator, put forth a new theory that could explain the origin and journey of this catastrophic object and others like it.<\/p>\n"],"rendered":"\n<p>In a <a href=\"http:\/\/www.nature.com\/articles\/s41598-021-82320-2\">study<\/a> published in Scientific Reports, <a href=\"https:\/\/astronomy.fas.harvard.edu\/people\/avi-loeb\">Avi Loeb<\/a>, Frank B. Baird Jr. Professor of Science at Harvard, and <a href=\"https:\/\/scholar.harvard.edu\/siraj\">Amir Siraj<\/a> \u201921, an astrophysics concentrator, put forth a new theory that could explain the origin and journey of this catastrophic object and others like it.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"Using statistical analysis and gravitational simulations, Loeb and Siraj say that a significant fraction of a type of comet originating from the Oort cloud, a sphere of debris at the edge of the solar system, was bumped off-course by Jupiter\u2019s gravitational field during its orbit and sent close to the sun, whose tidal force broke apart pieces of the rock. That increases the rate of comets like Chicxulub (pronounced Chicks-uh-lub) because these fragments cross the Earth\u2019s orbit and hit the planet once every 250 to 730 million years or so.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>Using statistical analysis and gravitational simulations, Loeb and Siraj say that a significant fraction of a type of comet originating from the Oort cloud, a sphere of debris at the edge of the solar system, was bumped off-course by Jupiter\u2019s gravitational field during its orbit and sent close to the sun, whose tidal force broke apart pieces of the rock. That increases the rate of comets like Chicxulub (pronounced Chicks-uh-lub) because these fragments cross the Earth\u2019s orbit and hit the planet once every 250 to 730 million years or so.<\/p>\n","innerContent":["\n<p>Using statistical analysis and gravitational simulations, Loeb and Siraj say that a significant fraction of a type of comet originating from the Oort cloud, a sphere of debris at the edge of the solar system, was bumped off-course by Jupiter\u2019s gravitational field during its orbit and sent close to the sun, whose tidal force broke apart pieces of the rock. That increases the rate of comets like Chicxulub (pronounced Chicks-uh-lub) because these fragments cross the Earth\u2019s orbit and hit the planet once every 250 to 730 million years or so.<\/p>\n"],"rendered":"\n<p>Using statistical analysis and gravitational simulations, Loeb and Siraj say that a significant fraction of a type of comet originating from the Oort cloud, a sphere of debris at the edge of the solar system, was bumped off-course by Jupiter\u2019s gravitational field during its orbit and sent close to the sun, whose tidal force broke apart pieces of the rock. That increases the rate of comets like Chicxulub (pronounced Chicks-uh-lub) because these fragments cross the Earth\u2019s orbit and hit the planet once every 250 to 730 million years or so.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"\u201cBasically, Jupiter acts as a kind of pinball machine,\u201d said Siraj, who is also co-president of <a href=\"http:\/\/www.hcs.harvard.edu\/~seds\/\">Harvard Students for the Exploration and Development of Space<\/a> and is pursuing a master\u2019s degree at the New England Conservatory of Music. \u201cJupiter kicks these incoming long-period comets into orbits that bring them very close to the sun.\u201d","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>\u201cBasically, Jupiter acts as a kind of pinball machine,\u201d said Siraj, who is also co-president of <a href=\"http:\/\/www.hcs.harvard.edu\/~seds\/\">Harvard Students for the Exploration and Development of Space<\/a> and is pursuing a master\u2019s degree at the New England Conservatory of Music. \u201cJupiter kicks these incoming long-period comets into orbits that bring them very close to the sun.\u201d<\/p>\n","innerContent":["\n<p>\u201cBasically, Jupiter acts as a kind of pinball machine,\u201d said Siraj, who is also co-president of <a href=\"http:\/\/www.hcs.harvard.edu\/~seds\/\">Harvard Students for the Exploration and Development of Space<\/a> and is pursuing a master\u2019s degree at the New England Conservatory of Music. \u201cJupiter kicks these incoming long-period comets into orbits that bring them very close to the sun.\u201d<\/p>\n"],"rendered":"\n<p>\u201cBasically, Jupiter acts as a kind of pinball machine,\u201d said Siraj, who is also co-president of <a href=\"http:\/\/www.hcs.harvard.edu\/~seds\/\">Harvard Students for the Exploration and Development of Space<\/a> and is pursuing a master\u2019s degree at the New England Conservatory of Music. \u201cJupiter kicks these incoming long-period comets into orbits that bring them very close to the sun.\u201d<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"It\u2019s because of this that long-period comets, which take more than 200 years to orbit the sun, are called sun grazers, he said.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>It\u2019s because of this that long-period comets, which take more than 200 years to orbit the sun, are called sun grazers, he said.<\/p>\n","innerContent":["\n<p>It\u2019s because of this that long-period comets, which take more than 200 years to orbit the sun, are called sun grazers, he said.<\/p>\n"],"rendered":"\n<p>It\u2019s because of this that long-period comets, which take more than 200 years to orbit the sun, are called sun grazers, he said.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"\u201cWhen you have these sun grazers, it\u2019s not so much the melting that goes on, which is a pretty small fraction relative to the total mass, but the comet is so close to the sun that the part that\u2019s closer to the sun feels a stronger gravitational pull than the part that is farther from the sun, causing a tidal force\u201d he said. \u201cYou get what\u2019s called a tidal disruption event and so these large comets that come really close to the sun break up into smaller comets. And basically, on their way out, there\u2019s a statistical chance that these smaller comets hit the Earth.\u201d","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>\u201cWhen you have these sun grazers, it\u2019s not so much the melting that goes on, which is a pretty small fraction relative to the total mass, but the comet is so close to the sun that the part that\u2019s closer to the sun feels a stronger gravitational pull than the part that is farther from the sun, causing a tidal force\u201d he said. \u201cYou get what\u2019s called a tidal disruption event and so these large comets that come really close to the sun break up into smaller comets. And basically, on their way out, there\u2019s a statistical chance that these smaller comets hit the Earth.\u201d<\/p>\n","innerContent":["\n<p>\u201cWhen you have these sun grazers, it\u2019s not so much the melting that goes on, which is a pretty small fraction relative to the total mass, but the comet is so close to the sun that the part that\u2019s closer to the sun feels a stronger gravitational pull than the part that is farther from the sun, causing a tidal force\u201d he said. \u201cYou get what\u2019s called a tidal disruption event and so these large comets that come really close to the sun break up into smaller comets. And basically, on their way out, there\u2019s a statistical chance that these smaller comets hit the Earth.\u201d<\/p>\n"],"rendered":"\n<p>\u201cWhen you have these sun grazers, it\u2019s not so much the melting that goes on, which is a pretty small fraction relative to the total mass, but the comet is so close to the sun that the part that\u2019s closer to the sun feels a stronger gravitational pull than the part that is farther from the sun, causing a tidal force\u201d he said. \u201cYou get what\u2019s called a tidal disruption event and so these large comets that come really close to the sun break up into smaller comets. And basically, on their way out, there\u2019s a statistical chance that these smaller comets hit the Earth.\u201d<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"The calculations from Loeb and Siraj\u2019s theory increase the chances of long-period comets impacting Earth by a factor of about 10, and show that about 20 percent of long-period comets become sun grazers. That finding falls in line with research from other astronomers.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>The calculations from Loeb and Siraj\u2019s theory increase the chances of long-period comets impacting Earth by a factor of about 10, and show that about 20 percent of long-period comets become sun grazers. That finding falls in line with research from other astronomers.<\/p>\n","innerContent":["\n<p>The calculations from Loeb and Siraj\u2019s theory increase the chances of long-period comets impacting Earth by a factor of about 10, and show that about 20 percent of long-period comets become sun grazers. That finding falls in line with research from other astronomers.<\/p>\n"],"rendered":"\n<p>The calculations from Loeb and Siraj\u2019s theory increase the chances of long-period comets impacting Earth by a factor of about 10, and show that about 20 percent of long-period comets become sun grazers. That finding falls in line with research from other astronomers.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"The pair claim that their new rate of impact is consistent with the age of Chicxulub, providing a satisfactory explanation for its origin and other impactors like it.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>The pair claim that their new rate of impact is consistent with the age of Chicxulub, providing a satisfactory explanation for its origin and other impactors like it.<\/p>\n","innerContent":["\n<p>The pair claim that their new rate of impact is consistent with the age of Chicxulub, providing a satisfactory explanation for its origin and other impactors like it.<\/p>\n"],"rendered":"\n<p>The pair claim that their new rate of impact is consistent with the age of Chicxulub, providing a satisfactory explanation for its origin and other impactors like it.<\/p>\n"},{"blockName":"core\/image","attrs":{"align":"center","id":314983,"sizeSlug":"full","className":"is-resized","creditText":"Harvard University","blob":"","url":"https:\/\/news.harvard.edu\/gazette\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg","alt":"Avi Loeb.","caption":"Understanding Chicxulub impactor is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again, contends Avi Loeb, Frank B. Baird Jr. Professor of Science at Harvard. Kris Snibbe\/Harvard file photo\t\t\t","lightbox":[],"title":"","href":"","rel":"","linkClass":"","width":"","height":"","aspectRatio":"","scale":"","linkDestination":"","linkTarget":"","lock":[],"metadata":[],"style":[],"borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<figure class=\"wp-block-image aligncenter size-full is-resized\"><img src=\"https:\/\/news.harvard.edu\/gazette\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg\" alt=\"Avi Loeb.\" class=\"wp-image-314983\"\/><figcaption class=\"wp-element-caption\">Understanding Chicxulub impactor is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again, contends Avi Loeb, Frank B. Baird Jr. Professor of Science at Harvard. Kris Snibbe\/Harvard file photo\t\t\t<\/figcaption><\/figure>\n","innerContent":["\n<figure class=\"wp-block-image aligncenter size-full is-resized\"><img src=\"https:\/\/news.harvard.edu\/gazette\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg\" alt=\"Avi Loeb.\" class=\"wp-image-314983\"\/><figcaption class=\"wp-element-caption\">Understanding Chicxulub impactor is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again, contends Avi Loeb, Frank B. Baird Jr. Professor of Science at Harvard. Kris Snibbe\/Harvard file photo\t\t\t<\/figcaption><\/figure>\n"],"rendered":"\n<figure class=\"wp-block-image aligncenter size-full is-resized\"><img src=\"https:\/\/news.harvard.edu\/gazette\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg\" alt=\"Avi Loeb.\" class=\"wp-image-314983\"\/><figcaption class=\"wp-element-caption\"><p class=\"wp-element-caption--caption\">Understanding Chicxulub impactor is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again, contends Avi Loeb, Frank B. Baird Jr. Professor of Science at Harvard. Kris Snibbe\/Harvard file photo\t\t\t<\/p><p class=\"wp-element-caption--credit\">Harvard University<\/p><\/figcaption><\/figure>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"\u201cOur paper provides a basis for explaining the occurrence of this event,\u201d Loeb said. \u201cWe are suggesting that, in fact, if you break up an object as it comes close to the sun, it could give rise to the appropriate event rate and also the kind of impact that killed the dinosaurs.\u201d","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>\u201cOur paper provides a basis for explaining the occurrence of this event,\u201d Loeb said. \u201cWe are suggesting that, in fact, if you break up an object as it comes close to the sun, it could give rise to the appropriate event rate and also the kind of impact that killed the dinosaurs.\u201d<\/p>\n","innerContent":["\n<p>\u201cOur paper provides a basis for explaining the occurrence of this event,\u201d Loeb said. \u201cWe are suggesting that, in fact, if you break up an object as it comes close to the sun, it could give rise to the appropriate event rate and also the kind of impact that killed the dinosaurs.\u201d<\/p>\n"],"rendered":"\n<p>\u201cOur paper provides a basis for explaining the occurrence of this event,\u201d Loeb said. \u201cWe are suggesting that, in fact, if you break up an object as it comes close to the sun, it could give rise to the appropriate event rate and also the kind of impact that killed the dinosaurs.\u201d<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"Loeb and Siraj\u2019s hypothesis might also explain the makeup of many of these impactors.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>Loeb and Siraj\u2019s hypothesis might also explain the makeup of many of these impactors.<\/p>\n","innerContent":["\n<p>Loeb and Siraj\u2019s hypothesis might also explain the makeup of many of these impactors.<\/p>\n"],"rendered":"\n<p>Loeb and Siraj\u2019s hypothesis might also explain the makeup of many of these impactors.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"\u201cOur hypothesis predicts that other Chicxulub-size craters on Earth are more likely to correspond to an impactor with a primitive (carbonaceous chondrite) composition than expected from the conventional main-belt asteroids,\u201d the researchers wrote in the paper.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>\u201cOur hypothesis predicts that other Chicxulub-size craters on Earth are more likely to correspond to an impactor with a primitive (carbonaceous chondrite) composition than expected from the conventional main-belt asteroids,\u201d the researchers wrote in the paper.<\/p>\n","innerContent":["\n<p>\u201cOur hypothesis predicts that other Chicxulub-size craters on Earth are more likely to correspond to an impactor with a primitive (carbonaceous chondrite) composition than expected from the conventional main-belt asteroids,\u201d the researchers wrote in the paper.<\/p>\n"],"rendered":"\n<p>\u201cOur hypothesis predicts that other Chicxulub-size craters on Earth are more likely to correspond to an impactor with a primitive (carbonaceous chondrite) composition than expected from the conventional main-belt asteroids,\u201d the researchers wrote in the paper.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"This is important because a popular theory on the origin of Chicxulub claims the impactor is a fragment of a much larger asteroid that came from the main belt, which is an asteroid population between the orbit of Jupiter and Mars. Only about a tenth of all main-belt asteroids have a composition of carbonaceous chondrite, while it\u2019s assumed most long-period comets have it. Evidence found at the Chicxulub crater and other similar craters that suggests they had carbonaceous chondrite.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>This is important because a popular theory on the origin of Chicxulub claims the impactor is a fragment of a much larger asteroid that came from the main belt, which is an asteroid population between the orbit of Jupiter and Mars. Only about a tenth of all main-belt asteroids have a composition of carbonaceous chondrite, while it\u2019s assumed most long-period comets have it. Evidence found at the Chicxulub crater and other similar craters that suggests they had carbonaceous chondrite.<\/p>\n","innerContent":["\n<p>This is important because a popular theory on the origin of Chicxulub claims the impactor is a fragment of a much larger asteroid that came from the main belt, which is an asteroid population between the orbit of Jupiter and Mars. Only about a tenth of all main-belt asteroids have a composition of carbonaceous chondrite, while it\u2019s assumed most long-period comets have it. Evidence found at the Chicxulub crater and other similar craters that suggests they had carbonaceous chondrite.<\/p>\n"],"rendered":"\n<p>This is important because a popular theory on the origin of Chicxulub claims the impactor is a fragment of a much larger asteroid that came from the main belt, which is an asteroid population between the orbit of Jupiter and Mars. Only about a tenth of all main-belt asteroids have a composition of carbonaceous chondrite, while it\u2019s assumed most long-period comets have it. Evidence found at the Chicxulub crater and other similar craters that suggests they had carbonaceous chondrite.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"This includes an object that hit about 2 billion years ago and left the Vredefort crater in South Africa, which is the largest confirmed crater in Earth\u2019s history, and the impactor that left the Zhamanshin crater in Kazakhstan, which is the largest confirmed crater within the last million years.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>This includes an object that hit about 2 billion years ago and left the Vredefort crater in South Africa, which is the largest confirmed crater in Earth\u2019s history, and the impactor that left the Zhamanshin crater in Kazakhstan, which is the largest confirmed crater within the last million years.<\/p>\n","innerContent":["\n<p>This includes an object that hit about 2 billion years ago and left the Vredefort crater in South Africa, which is the largest confirmed crater in Earth\u2019s history, and the impactor that left the Zhamanshin crater in Kazakhstan, which is the largest confirmed crater within the last million years.<\/p>\n"],"rendered":"\n<p>This includes an object that hit about 2 billion years ago and left the Vredefort crater in South Africa, which is the largest confirmed crater in Earth\u2019s history, and the impactor that left the Zhamanshin crater in Kazakhstan, which is the largest confirmed crater within the last million years.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"The researchers say that composition evidence supports their model and that the years the objects hit support both their calculations on impact rates of Chicxulub-sized tidally disrupted comets and for smaller ones like the impactor that made the Zhamanshin crater. If produced the same way, they say those would strike Earth once every 250,000 to 730,000 years.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>The researchers say that composition evidence supports their model and that the years the objects hit support both their calculations on impact rates of Chicxulub-sized tidally disrupted comets and for smaller ones like the impactor that made the Zhamanshin crater. If produced the same way, they say those would strike Earth once every 250,000 to 730,000 years.<\/p>\n","innerContent":["\n<p>The researchers say that composition evidence supports their model and that the years the objects hit support both their calculations on impact rates of Chicxulub-sized tidally disrupted comets and for smaller ones like the impactor that made the Zhamanshin crater. If produced the same way, they say those would strike Earth once every 250,000 to 730,000 years.<\/p>\n"],"rendered":"\n<p>The researchers say that composition evidence supports their model and that the years the objects hit support both their calculations on impact rates of Chicxulub-sized tidally disrupted comets and for smaller ones like the impactor that made the Zhamanshin crater. If produced the same way, they say those would strike Earth once every 250,000 to 730,000 years.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"Aside from composition of comets, the new Vera Rubin Observatory in Chile may be able to see the tidal disruption of long-period comets after it becomes operational next year.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>Aside from composition of comets, the new Vera Rubin Observatory in Chile may be able to see the tidal disruption of long-period comets after it becomes operational next year.<\/p>\n","innerContent":["\n<p>Aside from composition of comets, the new Vera Rubin Observatory in Chile may be able to see the tidal disruption of long-period comets after it becomes operational next year.<\/p>\n"],"rendered":"\n<p>Aside from composition of comets, the new Vera Rubin Observatory in Chile may be able to see the tidal disruption of long-period comets after it becomes operational next year.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"\u201cWe should see smaller fragments coming to Earth more frequently from the Oort cloud,\u201d Loeb said. \u201cI hope that we can test the theory by having more data on long-period comets, get better statistics, and perhaps see evidence for some fragments.\u201d","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>\u201cWe should see smaller fragments coming to Earth more frequently from the Oort cloud,\u201d Loeb said. \u201cI hope that we can test the theory by having more data on long-period comets, get better statistics, and perhaps see evidence for some fragments.\u201d<\/p>\n","innerContent":["\n<p>\u201cWe should see smaller fragments coming to Earth more frequently from the Oort cloud,\u201d Loeb said. \u201cI hope that we can test the theory by having more data on long-period comets, get better statistics, and perhaps see evidence for some fragments.\u201d<\/p>\n"],"rendered":"\n<p>\u201cWe should see smaller fragments coming to Earth more frequently from the Oort cloud,\u201d Loeb said. \u201cI hope that we can test the theory by having more data on long-period comets, get better statistics, and perhaps see evidence for some fragments.\u201d<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"Loeb said understanding this is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>Loeb said understanding this is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again.<\/p>\n","innerContent":["\n<p>Loeb said understanding this is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again.<\/p>\n"],"rendered":"\n<p>Loeb said understanding this is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"\u201cIt must have been an amazing sight, but we don\u2019t want to see that side,\u201d he said.","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p>\u201cIt must have been an amazing sight, but we don\u2019t want to see that side,\u201d he said.<\/p>\n","innerContent":["\n<p>\u201cIt must have been an amazing sight, but we don\u2019t want to see that side,\u201d he said.<\/p>\n"],"rendered":"\n<p>\u201cIt must have been an amazing sight, but we don\u2019t want to see that side,\u201d he said.<\/p>\n"},{"blockName":"core\/paragraph","attrs":{"align":"","content":"<em>This work was partially supported by the <\/em><a href=\"https:\/\/origins.harvard.edu\/\"><em>Harvard Origins of Life Initiative<\/em><\/a><em> and the Breakthrough Prize Foundation.<\/em>","dropCap":false,"placeholder":"","direction":"","lock":[],"metadata":[],"className":"","style":[],"backgroundColor":"","textColor":"","gradient":"","fontSize":"","fontFamily":"","borderColor":"","anchor":""},"innerBlocks":[],"innerHTML":"\n<p><em>This work was partially supported by the <\/em><a href=\"https:\/\/origins.harvard.edu\/\"><em>Harvard Origins of Life Initiative<\/em><\/a><em> and the Breakthrough Prize Foundation.<\/em><\/p>\n","innerContent":["\n<p><em>This work was partially supported by the <\/em><a href=\"https:\/\/origins.harvard.edu\/\"><em>Harvard Origins of Life Initiative<\/em><\/a><em> and the Breakthrough Prize Foundation.<\/em><\/p>\n"],"rendered":"\n<p><em>This work was partially supported by the <\/em><a href=\"https:\/\/origins.harvard.edu\/\"><em>Harvard Origins of Life Initiative<\/em><\/a><em> and the Breakthrough Prize Foundation.<\/em><\/p>\n"}],"innerHTML":"\n<div class=\"wp-block-group alignwide\">\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n<\/div>\n","innerContent":["\n<div class=\"wp-block-group alignwide\">","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","\n\n","<\/div>\n"],"rendered":"\n<div class=\"wp-block-group alignwide has-global-padding is-content-justification-center is-layout-constrained wp-block-group-is-layout-constrained\">\n<p>It was tens of miles wide and forever changed history when it crashed into Earth about 66 million years ago.<\/p>\n\n\n\n<p>The Chicxulub impactor, as it\u2019s known, was a plummeting asteroid or comet that left behind a crater off the coast of Mexico that spans 93 miles and goes 12 miles deep. Its devastating impact brought the reign of the dinosaurs to an abrupt and calamitous end, scientists say, by triggering their sudden mass extinction, along with the end of almost three-quarters of the plant and animal species then living on Earth.<\/p>\n\n\n\n<p>The enduring puzzle has always been where the asteroid or comet originated, and how it came to strike the Earth. And now a pair of Harvard researchers believe they have the answer.<\/p>\n\n\n\n<p>In a <a href=\"http:\/\/www.nature.com\/articles\/s41598-021-82320-2\">study<\/a> published in Scientific Reports, <a href=\"https:\/\/astronomy.fas.harvard.edu\/people\/avi-loeb\">Avi Loeb<\/a>, Frank B. Baird Jr. Professor of Science at Harvard, and <a href=\"https:\/\/scholar.harvard.edu\/siraj\">Amir Siraj<\/a> \u201921, an astrophysics concentrator, put forth a new theory that could explain the origin and journey of this catastrophic object and others like it.<\/p>\n\n\n\n<p>Using statistical analysis and gravitational simulations, Loeb and Siraj say that a significant fraction of a type of comet originating from the Oort cloud, a sphere of debris at the edge of the solar system, was bumped off-course by Jupiter\u2019s gravitational field during its orbit and sent close to the sun, whose tidal force broke apart pieces of the rock. That increases the rate of comets like Chicxulub (pronounced Chicks-uh-lub) because these fragments cross the Earth\u2019s orbit and hit the planet once every 250 to 730 million years or so.<\/p>\n\n\n\n<p>\u201cBasically, Jupiter acts as a kind of pinball machine,\u201d said Siraj, who is also co-president of <a href=\"http:\/\/www.hcs.harvard.edu\/~seds\/\">Harvard Students for the Exploration and Development of Space<\/a> and is pursuing a master\u2019s degree at the New England Conservatory of Music. \u201cJupiter kicks these incoming long-period comets into orbits that bring them very close to the sun.\u201d<\/p>\n\n\n\n<p>It\u2019s because of this that long-period comets, which take more than 200 years to orbit the sun, are called sun grazers, he said.<\/p>\n\n\n\n<p>\u201cWhen you have these sun grazers, it\u2019s not so much the melting that goes on, which is a pretty small fraction relative to the total mass, but the comet is so close to the sun that the part that\u2019s closer to the sun feels a stronger gravitational pull than the part that is farther from the sun, causing a tidal force\u201d he said. \u201cYou get what\u2019s called a tidal disruption event and so these large comets that come really close to the sun break up into smaller comets. And basically, on their way out, there\u2019s a statistical chance that these smaller comets hit the Earth.\u201d<\/p>\n\n\n\n<p>The calculations from Loeb and Siraj\u2019s theory increase the chances of long-period comets impacting Earth by a factor of about 10, and show that about 20 percent of long-period comets become sun grazers. That finding falls in line with research from other astronomers.<\/p>\n\n\n\n<p>The pair claim that their new rate of impact is consistent with the age of Chicxulub, providing a satisfactory explanation for its origin and other impactors like it.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full is-resized\"><img src=\"https:\/\/news.harvard.edu\/gazette\/wp-content\/uploads\/2020\/10\/092314_Avi-Loeb_007.jpg\" alt=\"Avi Loeb.\" class=\"wp-image-314983\"\/><figcaption class=\"wp-element-caption\"><p class=\"wp-element-caption--caption\">Understanding Chicxulub impactor is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again, contends Avi Loeb, Frank B. Baird Jr. Professor of Science at Harvard. Kris Snibbe\/Harvard file photo\t\t\t<\/p><p class=\"wp-element-caption--credit\">Harvard University<\/p><\/figcaption><\/figure>\n\n\n\n<p>\u201cOur paper provides a basis for explaining the occurrence of this event,\u201d Loeb said. \u201cWe are suggesting that, in fact, if you break up an object as it comes close to the sun, it could give rise to the appropriate event rate and also the kind of impact that killed the dinosaurs.\u201d<\/p>\n\n\n\n<p>Loeb and Siraj\u2019s hypothesis might also explain the makeup of many of these impactors.<\/p>\n\n\n\n<p>\u201cOur hypothesis predicts that other Chicxulub-size craters on Earth are more likely to correspond to an impactor with a primitive (carbonaceous chondrite) composition than expected from the conventional main-belt asteroids,\u201d the researchers wrote in the paper.<\/p>\n\n\n\n<p>This is important because a popular theory on the origin of Chicxulub claims the impactor is a fragment of a much larger asteroid that came from the main belt, which is an asteroid population between the orbit of Jupiter and Mars. Only about a tenth of all main-belt asteroids have a composition of carbonaceous chondrite, while it\u2019s assumed most long-period comets have it. Evidence found at the Chicxulub crater and other similar craters that suggests they had carbonaceous chondrite.<\/p>\n\n\n\n<p>This includes an object that hit about 2 billion years ago and left the Vredefort crater in South Africa, which is the largest confirmed crater in Earth\u2019s history, and the impactor that left the Zhamanshin crater in Kazakhstan, which is the largest confirmed crater within the last million years.<\/p>\n\n\n\n<p>The researchers say that composition evidence supports their model and that the years the objects hit support both their calculations on impact rates of Chicxulub-sized tidally disrupted comets and for smaller ones like the impactor that made the Zhamanshin crater. If produced the same way, they say those would strike Earth once every 250,000 to 730,000 years.<\/p>\n\n\n\n<p>Aside from composition of comets, the new Vera Rubin Observatory in Chile may be able to see the tidal disruption of long-period comets after it becomes operational next year.<\/p>\n\n\n\n<p>\u201cWe should see smaller fragments coming to Earth more frequently from the Oort cloud,\u201d Loeb said. \u201cI hope that we can test the theory by having more data on long-period comets, get better statistics, and perhaps see evidence for some fragments.\u201d<\/p>\n\n\n\n<p>Loeb said understanding this is not just crucial to solving a mystery of Earth\u2019s history but could prove pivotal if such an event were to threaten the planet again.<\/p>\n\n\n\n<p>\u201cIt must have been an amazing sight, but we don\u2019t want to see that side,\u201d he said.<\/p>\n\n\n\n<p><em>This work was partially supported by the <\/em><a href=\"https:\/\/origins.harvard.edu\/\"><em>Harvard Origins of Life Initiative<\/em><\/a><em> and the Breakthrough Prize Foundation.<\/em><\/p>\n<\/div>\n"}},"jetpack-related-posts":[{"id":165741,"url":"https:\/\/news.harvard.edu\/gazette\/story\/2015\/02\/twice-doomed\/","url_meta":{"origin":312848,"position":0},"title":"Twice doomed?","author":"harvardgazette","date":"February 4, 2015","format":false,"excerpt":"Growing evidence points to a role for volcanoes in dinosaur extinction, said planetary scientist Mark Richards in a Harvard lecture.","rel":"","context":"In &quot;Health&quot;","block_context":{"text":"Health","link":"https:\/\/news.harvard.edu\/gazette\/section\/health\/"},"img":{"alt_text":"","src":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2015\/02\/020315_extinct_056_605.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2015\/02\/020315_extinct_056_605.jpg?resize=350%2C200 1x, https:\/\/news.harvard.edu\/wp-content\/uploads\/2015\/02\/020315_extinct_056_605.jpg?resize=525%2C300 1.5x"},"classes":[]},{"id":258967,"url":"https:\/\/news.harvard.edu\/gazette\/story\/2018\/11\/tiny-teeth-tell-the-story-of-two-fish-species-rapid-evolution\/","url_meta":{"origin":312848,"position":1},"title":"Fish teeth mark periods of evolution","author":"harvardgazette","date":"November 16, 2018","format":false,"excerpt":"Based on close examination of thousands of fossilized fish teeth, a Harvard researcher found that, while the asteroid impact that killed off the dinosaurs did lead to the extinction of some fish species, it also set the stage for two periods of rapid evolution among marine life.","rel":"","context":"In &quot;Science &amp; Tech&quot;","block_context":{"text":"Science &amp; Tech","link":"https:\/\/news.harvard.edu\/gazette\/section\/science-technology\/"},"img":{"alt_text":"Fish teeth","src":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2018\/11\/Fish-teeth.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2018\/11\/Fish-teeth.jpg?resize=350%2C200 1x, https:\/\/news.harvard.edu\/wp-content\/uploads\/2018\/11\/Fish-teeth.jpg?resize=525%2C300 1.5x, https:\/\/news.harvard.edu\/wp-content\/uploads\/2018\/11\/Fish-teeth.jpg?resize=700%2C400 2x"},"classes":[]},{"id":175086,"url":"https:\/\/news.harvard.edu\/gazette\/story\/2015\/10\/randall-follows-dramatic-chain-of-events\/","url_meta":{"origin":312848,"position":2},"title":"Dramatic chain of events","author":"harvardgazette","date":"October 26, 2015","format":false,"excerpt":"Harvard physicist Lisa Randall discusses the research behind her new book, \u201cDark Matter and the Dinosaurs.\u201d","rel":"","context":"In &quot;Science &amp; Tech&quot;","block_context":{"text":"Science &amp; Tech","link":"https:\/\/news.harvard.edu\/gazette\/section\/science-technology\/"},"img":{"alt_text":"","src":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2015\/10\/101415_randall_lisa_167_605.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2015\/10\/101415_randall_lisa_167_605.jpg?resize=350%2C200 1x, https:\/\/news.harvard.edu\/wp-content\/uploads\/2015\/10\/101415_randall_lisa_167_605.jpg?resize=525%2C300 1.5x"},"classes":[]},{"id":346824,"url":"https:\/\/news.harvard.edu\/gazette\/story\/2022\/08\/climate-change-drove-reptile-evolution\/","url_meta":{"origin":312848,"position":3},"title":"Why were reptiles such evolution success story?","author":"gazettebeckycoleman","date":"August 29, 2022","format":false,"excerpt":"Fast climatic shifts due to global warming coincided with high rates of morphological change in most reptiles.","rel":"","context":"In &quot;Science &amp; Tech&quot;","block_context":{"text":"Science &amp; Tech","link":"https:\/\/news.harvard.edu\/gazette\/section\/science-technology\/"},"img":{"alt_text":"Artistic rendering of of carnivorous reptile that was a close relative of crocodiles and dinosaurs chasing a gliding reptile in a hot and dry river valley 240 million years ago.","src":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2022\/08\/Fig1_EcosystemReconstructionCredit_HenrySharpe_2500.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2022\/08\/Fig1_EcosystemReconstructionCredit_HenrySharpe_2500.jpg?resize=350%2C200 1x, https:\/\/news.harvard.edu\/wp-content\/uploads\/2022\/08\/Fig1_EcosystemReconstructionCredit_HenrySharpe_2500.jpg?resize=525%2C300 1.5x, https:\/\/news.harvard.edu\/wp-content\/uploads\/2022\/08\/Fig1_EcosystemReconstructionCredit_HenrySharpe_2500.jpg?resize=700%2C400 2x"},"classes":[]},{"id":383356,"url":"https:\/\/news.harvard.edu\/gazette\/story\/2024\/04\/early-warning-sign-of-extinction\/","url_meta":{"origin":312848,"position":4},"title":"Early warning sign of extinction?","author":"harvardgazette","date":"April 24, 2024","format":false,"excerpt":"Fossil record stretching millions of years shows tiny ocean creatures on the move before Earth heats up","rel":"","context":"In &quot;Science &amp; Tech&quot;","block_context":{"text":"Science &amp; Tech","link":"https:\/\/news.harvard.edu\/gazette\/section\/science-technology\/"},"img":{"alt_text":"Planktonic foraminifera fossils.","src":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2024\/04\/planktonic-foraminifera.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/news.harvard.edu\/wp-content\/uploads\/2024\/04\/planktonic-foraminifera.jpg?resize=350%2C200 1x, https:\/\/news.harvard.edu\/wp-content\/uploads\/2024\/04\/planktonic-foraminifera.jpg?resize=525%2C300 1.5x, https:\/\/news.harvard.edu\/wp-content\/uploads\/2024\/04\/planktonic-foraminifera.jpg?resize=700%2C400 2x"},"classes":[]},{"id":57102,"url":"https:\/\/news.harvard.edu\/gazette\/story\/1999\/10\/what-killed-the-dinosaurs\/","url_meta":{"origin":312848,"position":5},"title":"What killed the dinosaurs?","author":"harvardgazette","date":"October 14, 1999","format":false,"excerpt":"Charles Marshall's childhood passion led him to a career in paleontology, trying to understand the interplay between inheritance, environment, and catastrophe in directing evolution. Marshall's work attracted media attention in 1996. He and University of Washington geologist Peter Ward concluded there may have been other causes than just the well-publicized\u2026","rel":"","context":"In &quot;Science &amp; Tech&quot;","block_context":{"text":"Science &amp; Tech","link":"https:\/\/news.harvard.edu\/gazette\/section\/science-technology\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/posts\/312848","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/users\/131912115"}],"replies":[{"embeddable":true,"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/comments?post=312848"}],"version-history":[{"count":21,"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/posts\/312848\/revisions"}],"predecessor-version":[{"id":369244,"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/posts\/312848\/revisions\/369244"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/media\/315067"}],"wp:attachment":[{"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/media?parent=312848"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/categories?post=312848"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/tags?post=312848"},{"taxonomy":"format","embeddable":true,"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/gazette-formats?post=312848"},{"taxonomy":"series","embeddable":true,"href":"https:\/\/news.harvard.edu\/gazette\/wp-json\/wp\/v2\/series?post=312848"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}