{"id":6464,"date":"2013-11-14T14:57:22","date_gmt":"2013-11-14T21:57:22","guid":{"rendered":"http:\/\/planets.ucla.edu\/?p=6464"},"modified":"2021-01-18T01:35:53","modified_gmt":"2021-01-18T09:35:53","slug":"researchers-use-the-oldest-minerals-on-earth-to-decode-solar-system-history","status":"publish","type":"post","link":"http:\/\/planets.ucla.edu\/?p=6464","title":{"rendered":"Researchers use oldest minerals on Earth to study solar system history"},"content":{"rendered":"

\"\"<\/a>The answer to one of the great mysteries of our solar system\u2019s history may lie within a grain no wider than a single strand of human hair.\u00a0 Scientists have long known that the mineral zircon is very hardy.\u00a0 \u201cZircon tends to stick around for a long time,\u201d said Beth Ann Bell, a fifth-year UCLA graduate student who studies these tiny grains.\u00a0 And she\u2019s not kidding about zircon\u2019s longevity \u2013 the samples she studies are 3.8 to 3.9 billion years old.\u00a0 The Earth itself is 4.5 billion years old.<\/p>\n

With their advisor, UCLA Professor Mark Harrison, Bell and her colleagues study individual zircon grains to better understand a critical and highly controversial event in our solar system\u2019s history known as the Late Heavy Bombardment (LHB).\u00a0 During the LHB, which occurred between 3.8 and 4.1 billion years ago, a very large number of craters formed on the surface of the Moon.\u00a0 Analysis of the craters and lunar samples have led some scientists to suggest that the objects that crashed into the Moon were numerous and came from far away, possibly beyond the orbit of Jupiter.\u00a0 \u201cThe whole inner solar system should have been impacted and evidence of the LHB should be detectable anywhere, even on Earth\u201c said Matthew Wielicki, also a fifth-year graduate student.\u00a0 But scientists are still uncertain if the LHB actually happened at all.\u00a0 \u201cThere is much debate among planetary scientists as to whether the lunar samples from NASA\u2019s Apollo mission are giving us the full picture of what was happening at that time,\u201d said Wielicki.<\/p>\n

To better understand the LHB, Wielicki and Bell analyze zircons on Earth in an attempt to determine whether any of the objects that formed the Moon\u2019s craters also impacted our planet.\u00a0 Like tiny little clocks, zircons can record the timing of an impact event by the heat signatures it leaves behind.\u00a0 Some recorded features, known as shock features, are diagnostic of an impact and can cause a grain to appear as though it was shattered.\u00a0 However, such telltale signs do not always develop, and scientists must instead investigate subtler signs, like the ratios of radioactive elements inside the zircon.<\/p>\n

To study element ratios within their zircon grains, Bell and Wielicki use a unique device called a Secondary Ion Mass Spectrometer (SIMS), located at UCLA. \u201cWith many techniques you must pulverize your sample, essentially destroying it, in order to study it,\u201d said Bell. With the SIMS, samples are left intact and shot with a beam of energized atoms, or ions, and analyzed in tiny patches.\u00a0 The SIMS can peer into a grain \u201cone atomic layer at a time,\u201d allowing them to study multiple heating events in a single zircon, said Wielicki.<\/p>\n

Cosmic impacts aren\u2019t the only events in Earth\u2019s history that could produce heat signatures in zircon grains.\u00a0 Using the SIMS, Bell and Wielicki hope to be able to distinguish between zircon grains that have been affected by a meteor impact and those that have been heated by \u201csome other event, like mountain building or volcanism, all which were occurring on Earth during the LHB timeframe.\u201d<\/p>\n

Because of efficient weathering and erosion processes, there are no impact craters on Earth which date back to the LHB, so Wielicki works to develop the tools necessary to understand impact-heated zircon grains using zircons from more recent impact events.\u00a0 Bell then tests the validity of those tools on LHB-age zircons whose history is unknown. \u201cThe rocks where we find ancient samples are sedimentary, which means they were once older rocks that eroded, and then turned into the sandstone we see today,\u201d said Bell, \u201cwe don\u2019t know what types of rock they originally grew in.\u201d<\/p>\n

\u201cWe are cornering two parts of a three-fold approach to pin down the LHB,\u201d said Wielicki. The third piece of their approach involves studying zircons from other inner solar system objects. \u201cThe real excitement comes when we apply our analytical tools to samples from objects like Vesta,\u201d said Wielicki.\u00a0 Vesta, the target of NASA\u2019s Dawn mission, is a large asteroid located in the inner solar system that has been cold for a very long time.\u00a0 Wielicki said, \u201cIf we see any heating signal in Vesta\u2019s zircons, we know it must be from an impact.\u201d<\/p>\n

For Bell and Wielicki, the picture is far from complete. The LHB, which occurred just before the onset of life on Earth, could have ties to the origins of life.\u00a0 It is unclear, however, if impacts would have acted as \u201clife frustrators,\u201d slowing life\u2019s development, or if they actually delivered the \u201cbuilding blocks\u201d for life, said Wielicki.\u00a0 \u201cUnderstanding the timing of the LHB may help answer some of the questions about life on Earth, but first we need a better understanding of the impact history for the inner solar system,\u201d he said.<\/p>\n

Watch a video profile of Matt Wielicki here<\/a>.\u00a0 Learn more about his research here<\/a>.<\/p>\n

Watch a video profile of Beth Ann Bell here<\/a>.\u00a0 Learn more about her research here<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

The answer to one of the great mysteries of our solar system\u2019s history may lie within a grain no wider than a single strand of human hair.\u00a0 Scientists have long known that the mineral zircon is very hardy.\u00a0 \u201cZircon tends to stick around for a long time,\u201d said Beth Ann Bell, a fifth-year UCLA graduate … <\/p>\n

Continue reading “Researchers use oldest minerals on Earth to study solar system history”<\/span><\/a><\/p>\n","protected":false},"author":9,"featured_media":1813,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[296,32],"tags":[340,338,339,337],"class_list":["post-6464","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-featured","category-news","tag-beth-ann-bell","tag-lhb","tag-matthew-wielicki","tag-zircon"],"_links":{"self":[{"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=\/wp\/v2\/posts\/6464","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6464"}],"version-history":[{"count":11,"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=\/wp\/v2\/posts\/6464\/revisions"}],"predecessor-version":[{"id":11317,"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=\/wp\/v2\/posts\/6464\/revisions\/11317"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=\/wp\/v2\/media\/1813"}],"wp:attachment":[{"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6464"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6464"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/planets.ucla.edu\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6464"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}