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That origin story rewrites where the most common space rocks came from, and ties their birth to the most violent chapter in the solar system\u2019s history. <\/p>\n
It also carries real stakes, because these are the same asteroids that humanity may one day need to deflect or mine.<\/p>\n
A century-old puzzle<\/p>\n
Crack open one of these meteorites and you find it studded<\/a> with chondrules. These are round beads of rock, most no wider than a fraction of an inch, that were once molten and then frozen solid. <\/p>\n They took shape at the very dawn of the solar system, roughly 4.6 billion years ago.<\/p>\n For more than a century, chondrules have posed two stubborn problems. First, what melted primitive dust into liquid droplets in the cold of space?<\/p>\n Second, why did those droplets end up so tightly packed inside the asteroids that carry them?<\/p>\n Earlier research<\/a> had shown that the parent bodies came together fast and early in the solar system. <\/p>\n The research did not explain why chondritic meteorites from every direction carry nearly the same heavy dose of chondrules.<\/p>\n Samples from across the asteroid belt<\/p>\n Hal Levison, a planetary scientist at the Southwest Research Institute (SwRI<\/a>) in Boulder, Colorado, had long been struck by that sameness. <\/p>\n Ordinary chondrites, the most common kind, can be more than half chondrules by volume, and samples from across the asteroid belt repeat the pattern.<\/p>\n \u201cI have always been surprised by how homogeneous the chondritic asteroids seem to be,\u201d said Levison.<\/p>\n His team set out to find a natural way to herd loose droplets into asteroid-sized bodies. That search led them to the era when the planets were still forming.<\/p>\n Born from giant impacts<\/p>\n The team believes the answer lies in the solar system\u2019s messiest stretch, the final act of building the rocky planets.<\/p>\n This was a crowded time. Simulations place it within the first few million years, when the inner solar system was packed with planetary embryos<\/a>. <\/p>\n These bodies, from Moon-sized to Mars-sized, kept crashing into one another.<\/p>\n When two embryos collide in the model, the impact throws out enormous sheets of melted and solid rock. <\/p>\n Much of it escapes, but a large share stays bound by gravity to the surviving body and settles into a flat, spinning ring of debris around it.<\/p>\n Beads of rock in the ring<\/p>\n That ring is where the puzzle comes apart. The molten droplets scattered into it would cool over hours, not the instants or ages that rival theories struggle with. <\/p>\n An earlier paper<\/a> had already shown that impacts alone can melt rock into chondrule-sized beads at just that pace.<\/p>\n Inside the ring, the beads clump into ever-larger objects, the same way dust once clumped around the young Sun to build planets. <\/p>\n They grow into asteroid-sized moons orbiting the still-forming embryo, and made almost entirely of debris from the original crash.<\/p>\n Out of the simulations, these moons match real chondritic asteroids in both size and makeup. <\/p>\n \u201cThis process parallels the formation of Mars\u2019 moons, Phobos and Deimos,\u201d said Levison, pointing to the two small satellites that circle the red planet.<\/p>\n Moons that broke free<\/p>\n The model\u2019s boldest step is what happens next. <\/p>\n These newly built moons did not stay put, because the early inner solar system was a gravitational free-for-all, with embryos constantly passing close to one another.<\/p>\n During those close passes, the simulations show, a moon could be torn from its host and thrown into its own orbit around the Sun. <\/p>\n Most did not survive as satellites. Between 60 and 95 percent escaped this way, while the rest fell back and merged into the embryo that made them.<\/p>\n Escaped moons become parent asteroids<\/p>\n The escapees, in this picture, became the parent bodies of the chondritic meteorites we collect. <\/p>\n Until this study, no single model had traced them from a planetary collision all the way to an independent asteroid. <\/p>\n This model also explains both how their chondrules formed and why they sit so densely inside.<\/p>\n Their long afterlife slowly ground them down. Over billions of years in the asteroid belt they chipped away at one another. <\/p>\n In addition, the sunlight itself, soaked up and thrown back off their surfaces as heat, slowly spun the smaller ones faster until fragments broke free and drifted toward Earth.<\/p>\n Those fragments are the chondritic meteorites now sitting in museum drawers and collectors\u2019 hands. <\/p>\n \u201cChondritic asteroids are not leftover random rubble from the solar nebula,\u201d said Kevin Walsh, a co-author on the study.<\/p>\n Asteroid structure could impact deflection<\/p>\n If chondritic asteroids really are wrecked mini-moons, the consequences run well beyond meteorite science. <\/p>\n They are also the most common near-Earth objects<\/a>, the very population that planetary-defense planners watch most closely.<\/p>\n How an asteroid answers a shove, whether from a spacecraft slammed into it or a nuclear blast, depends on what it is made of and how tightly it holds together. <\/p>\n A body assembled from impact debris and broken moons may be built very differently than one imagined to have grown gently from drifting dust.<\/p>\n That difference could change the sums behind a real deflection test<\/a>, and the same uncertainty hangs over any plan to mine such asteroids for metal. <\/p>\n Engineers drawing up either kind of mission lean on structural models that this work would revise.<\/p>\n What the finding changes<\/p>\n The model is not the final word. It is a computer simulation showing that the whole sequence is physically possible and fits what chondrites look like, not yet a fingerprint proving it happened. <\/p>\n Material returned from the asteroids Bennu and Ryugu could soon check its predictions against real samples.<\/p>\n What has changed is the origin story itself. The most ordinary rocks that fall from the sky now look like relics of the collisions that assembled the planets, each one a splinter of a lost moon. <\/p>\n Read that way, each chondrite becomes a record of how the rocky planets were made. <\/p>\n \u201cThey are escaped satellites \u2013 former moons-in-the-making \u2013 that carry within them a detailed record of the violent processes that built the terrestrial planets,\u201d said Rogerio Deienno, co-author of the study.<\/p>\n The study is published in the journal Science Advances<\/a>.<\/p>\n Image Credit: NASA\/JPL-Caltech\/T. Pyle (SSC)<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"The chondritic meteorites that land on Earth most often are the shattered remains of tiny moons that once…\n","protected":false},"author":2,"featured_media":564560,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[61,60,82,247],"class_list":["post-564559","post","type-post","status-publish","format-standard","has-post-thumbnail","category-space","tag-ie","tag-ireland","tag-science","tag-space"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/564559","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=564559"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/564559\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/564560"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=564559"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=564559"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=564559"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}