Scientists widely agree that an ancient planet likely smashed into Earth as it was forming billions of years ago, spewing debris that coalesced into the moon that decorates our night sky today. <\/p>\n
The theory, called the giant-impact hypothesis, explains many fundamental features of the moon and Earth. <\/p>\n
But one glaring mystery at the center of this hypothesis has endured: What ever happened to Theia? Direct evidence of its existence has remained elusive. No leftover fragments from the planet have been found in the solar system. And many scientists assumed any debris Theia left behind on Earth was blended in the fiery cauldron of our planet\u2019s interior. <\/p>\n
A new theory, however, suggests that remnants of the ancient planet remain partially intact, buried beneath our feet. <\/p>\n
Molten slabs of Theia could have embedded themselves within Earth\u2019s mantle after impact before solidifying, leaving portions of the ancient planet\u2019s material resting above Earth\u2019s core some 1,800 miles (about 2,900 kilometers) below the surface, according to a study published Wednesday in the journal Nature. <\/p>\n
If the theory is correct, it would not only provide additional details to fill out the giant-impact hypothesis but also answer a lingering question for geophysicists. <\/p>\n
They were already aware that there are\u00a0two massive, distinct blobs that are embedded deep within the Earth.\u00a0The masses \u2014 called large low-velocity provinces, or LLVPs \u2014 were first detected in the 1980s. One lies beneath Africa and another below the Pacific Ocean. <\/p>\n
These blobs are thousands of kilometers wide and likely more dense with iron compared with the surrounding mantle, <\/strong>making them stand out when measured by seismic waves. But the origins of the blobs \u2014 each of which are larger than the moon \u2014 remain a mystery to scientists. <\/p>\n But for Dr. Qian Yuan, a geophysicist and postdoctoral fellow at the California Institute of Technology and the new study\u2019s lead author, his understanding of LLVPs forever changed when he attended a 2019 seminar at Arizona State University, his alma mater, that outlined the giant-impact hypothesis. <\/p>\n That\u2019s when he learned new details about Theia, the mysterious projectile that presumably struck Earth billions of years ago. <\/p>\n And, as a trained geophysicist, he knew of those mysterious blobs hidden in Earth\u2019s mantle. <\/p>\n Yuan had a eureka moment, he said. <\/p>\n Immediately, he began perusing scientific studies, searching to see whether someone else had proposed that LLVPs might be fragments of Theia. But no one had. <\/p>\n Initially, Yuan said, he only told his adviser about his theory. <\/p>\n \u201cI was afraid of turning to other people because I (was) afraid others would think I\u2019m too crazy,\u201d Yuan said. <\/p>\n Yuan first proposed his idea in a paper he submitted in 2021. It was rejected three times. Peer reviewers said it lacked sufficient modeling from the giant impact. <\/p>\n Then he came across scientists who did just the type of research Yuan needed. <\/p>\n Their work, which assigned a certain size to Theia and speed of impact in the modeling, suggested that the ancient planet\u2019s collision likely did not entirely melt Earth\u2019s mantle, allowing the remnants of Theia to cool and form solid structures instead of blending together in Earth\u2019s inner stew. <\/p>\n \u201cEarth\u2019s mantle is rocky, but it isn\u2019t like solid rock,\u201d said Dr. Steve Desch, a study coauthor and professor of astrophysics at Arizona State\u2019s School of Earth and Space Exploration. \u201cIt\u2019s this high-pressure magma that\u2019s kind of gooey and has the viscosity of peanut butter, and it\u2019s basically sitting on a very hot stove.\u201d <\/p>\n In that environment, if the material that makes up the LLVPs was too dense, it wouldn\u2019t be able to pile up in the jagged formations that it appears in, Desch said. And if it were low enough in density, it would simply mix in with the churning mantle. <\/p>\n The question was this: What would be the density of the material left behind by Theia? And could it match up with the density of the LLVPs? <\/p>\n (Desch had authored his own paper in 2019 that sought to describe the density of the material that Theia would have left behind.) <\/p>\n The researchers sought higher-definition modeling with 100 to 1,000 times more resolution than their previous attempts, Yuan said. And still, the calculations lined up: If Theia were a certain size and consistency, and struck the Earth at a specific speed, the models showed it could, in fact, leave behind massive hunks of its guts within Earth\u2019s mantle and also spawn the debris that would go on to create our moon. <\/p>\n \u201cThat was very, very, so very exciting,\u201d Yuan said. \u201cThat (modeling) hadn\u2019t been done before.\u201d <\/p>\n The study Yuan published this week includes coauthors from a variety of disciplines across a range of institutions, including Arizona State, Caltech, the Shanghai Astronomical Observatory and NASA\u2019s Ames Research Center. <\/p>\n When asked whether he expects to encounter pushback or controversy over such a novel concept \u2014 that slabs of material from an ancient extraterrestrial planet are hidden deep within the Earth \u2014 Yuan replied: \u201cI also want to stress this is an idea; this is a hypothesis. <\/p>\n \u201cThere\u2019s no way to prove this must be the case,\u201d he added. \u201cI welcome other people to do this (research).\u201d <\/p>\n Desch added that, in his view, \u201cthis work is compelling. It makes a very strong case.\u201d It even seems \u201csort of obvious in hindsight.\u201d <\/p>\n Dr. Seth Jacobson, an assistant professor of planetary science at Michigan State University, acknowledged that the theory may not, however, soon reach broad acceptance. <\/p>\n \u201cThese (LLVPs) \u2014 they\u2019re an area themselves of very active research,\u201d said Jacobson, who was not involved in the study. And the tools used to study them are constantly evolving. <\/p>\n The idea that Theia created the LLVPs is no doubt an exciting and eye-catching hypothesis, he added, but it\u2019s not the only one out there. <\/p>\n One other theory, for example, posits that LLVPs are actually heaps of oceanic crust that have sunk to the depths of the mantle over billions of years. <\/p>\n \u201cI doubt the advocates for other hypotheses (about LLVP formation) are going to abandon them just because this one has appeared,\u201d Jacobson added. \u201cI think we\u2019ll be debating this for quite some time.\u201d <\/p>\n\n Scientists widely agree that an ancient planet likely smashed into Earth as it was forming billions of years ago, spewing debris that coalesced into the moon that decorates our night sky today. The theory, called the giant-impact hypothesis, explains many fundamental features of the moon and Earth. But one glaring mystery at the center of <\/p>\n","protected":false},"author":0,"featured_media":11150,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[],"class_list":{"0":"post-11149","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-world"},"_links":{"self":[{"href":"https:\/\/shareperformanceinsight.com\/index.php\/wp-json\/wp\/v2\/posts\/11149","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/shareperformanceinsight.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/shareperformanceinsight.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/shareperformanceinsight.com\/index.php\/wp-json\/wp\/v2\/comments?post=11149"}],"version-history":[{"count":0,"href":"https:\/\/shareperformanceinsight.com\/index.php\/wp-json\/wp\/v2\/posts\/11149\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/shareperformanceinsight.com\/index.php\/wp-json\/wp\/v2\/media\/11150"}],"wp:attachment":[{"href":"https:\/\/shareperformanceinsight.com\/index.php\/wp-json\/wp\/v2\/media?parent=11149"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/shareperformanceinsight.com\/index.php\/wp-json\/wp\/v2\/categories?post=11149"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/shareperformanceinsight.com\/index.php\/wp-json\/wp\/v2\/tags?post=11149"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} Interdisciplinary research<\/h3>\n
Building a theory<\/h3>\n