{"id":6173,"date":"2015-09-12T03:59:37","date_gmt":"2015-09-12T03:59:37","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=6173"},"modified":"2015-09-12T03:59:37","modified_gmt":"2015-09-12T03:59:37","slug":"moons-crust-as-fractured-as-can-be","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/moons-crust-as-fractured-as-can-be\/","title":{"rendered":"Moon\u2019s crust as fractured as can be"},"content":{"rendered":"

Study finds barrage of small asteroids shattered moon\u2019s upper crust.<\/strong><\/span><\/p>\n

\"Researchers<\/a>
Researchers analyzed the gravity signatures of more than 1,200 craters (in yellow) on the far side of the moon.
Courtesy of the researchers<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. —\u00a0Scientists believe that about 4 billion years ago, during a period called the Late Heavy Bombardment, the moon took a severe beating, as an army of asteroids pelted its surface, carving out craters and opening deep fissures in its crust. Such sustained impacts increased the moon\u2019s porosity, opening up a network of large seams beneath the lunar surface.<\/span><\/p>\n

Now scientists at MIT and elsewhere have identified regions on the far side of the moon, called the lunar highlands, that may have been so heavily bombarded \u2014 particularly by small asteroids \u2014 that the impacts completely shattered the upper crust, leaving these regions essentially as fractured and porous as they could be. The scientists found that further impacts to these highly porous regions may have then had the opposite effect, sealing up cracks and decreasing porosity.<\/span><\/p>\n

The researchers observed this effect in the upper layer of the crust \u2014 a layer that scientists refer to as the megaregolith. This layer is dominated by relatively small craters, measuring 30 kilometers or less in diameter. In contrast, it appears that deeper layers of crust, that are affected by larger craters, are not quite as battered, and are less fractured and porous.<\/span><\/p>\n

Jason Soderblom, a research scientist in MIT\u2019s Department of Earth, Atmospheric and Planetary Sciences, says the evolution of the moon\u2019s porosity can give scientists clues to some of the earliest life-supporting processes taking place in the solar system.<\/span><\/p>\n

\u201cThe whole process of generating pore space within planetary crusts is critically important in understanding how water gets into the subsurface,\u201d Soderblom says. \u201cOn Earth, we believe that life may have evolved somewhat in the subsurface, and this is a primary mechanism to create subsurface pockets and void spaces, and really drives a lot of the rates at which these processes happen. The moon is a really ideal place to study this.\u201d<\/span><\/p>\n

Soderblom and his colleagues, including Maria Zuber, the E.A. Griswold Professor of Geophysics and MIT\u2019s vice president for research, have published their findings in the journal\u00a0Geophysical Research Letters.<\/em><\/span><\/p>\n

Changing porosity<\/strong><\/span><\/p>\n

The team used data obtained by NASA\u2019s Gravity Recovery and Interior Laboratory (GRAIL) \u2014 twin spacecraft that orbited the moon throughout 2012, each measuring the push and pull of the other as an indicator of the moon\u2019s gravity.<\/span><\/p>\n

With the GRAIL data, researchers mapped the gravity field in and around more than 1,200 craters on the far side of the moon. This region, the lunar highlands, makes up the moon\u2019s most ancient, heavily cratered terrain.<\/span><\/p>\n

They then carried out an analysis called a Bouger correction to subtract the gravitational effect of mountains, valleys, and other topology from the total gravity field. What\u2019s left is the gravity field beneath the surface, within the moon\u2019s crust.<\/span><\/p>\n

\u201cThere\u2019s an assumption we do have to make, which is that there\u2019s no changes in the material itself, and that all of the bumps we\u2019re seeing [in the gravity field] are from changes in the porosity and the amount of air between the rock,\u201d Soderblom explains.<\/span><\/p>\n

Soderblom calculated the gravity signatures in and around 1,200 craters on the far side of the moon, and compared the gravity within each crater with the gravity of the surrounding terrain, to determine whether an impact increased or decreased the local porosity.<\/span><\/p>\n

Origin story<\/strong><\/span><\/p>\n

For craters smaller than 30 kilometers in diameter, he found impacts both increased and decreased porosity in the upper layer of the moon\u2019s crust.<\/span><\/p>\n

\u201cFor the smallest craters that we\u2019re looking at, we think we\u2019re starting to see where the moon has gone through so much fracturing that it gets to a point where the porosity of the crust just stays at some constant level,\u201d Soderblom says. \u201cYou can keep impacting it and you\u2019ll hit regions where you\u2019ll increase porosity here and decrease it there, but on average it stays constant.\u201d<\/span><\/p>\n

The researchers found that larger craters, which excavated much deeper into the moon\u2019s crust, only increased porosity in the underlying crust \u2014 an indication that these deeper layers have not reached a steady state in porosity, and are not as fractured as the megaregolith.<\/span><\/p>\n

Soderblom says the gravity signatures of the larger craters in particular may provide insight into just how many impacts the moon, and other terrestrial bodies, sustained during the Late Heavy Bombardment.<\/span><\/p>\n

\u201cFor the smaller craters, it\u2019s like if you\u2019re filling a bucket, eventually your bucket gets full, but if you keep pouring cups of water into the bucket, you can\u2019t tell how many cups of water beyond full you\u2019ve gone,\u201d Soderblom says. \u201cLooking at the larger craters at the subsurface might give us insight, because that \u2018bucket\u2019 isn\u2019t full yet.\u201d<\/span><\/p>\n

Ultimately, tracing the moon\u2019s changing porosity may help scientists track the trajectory of the moon\u2019s impactors 4 billion years ago.<\/span><\/p>\n

\u201cWhat we really hope to do is to figure out the number of impacts in the range of 100 kilometers in diameter, and from that, we can extrapolate to the smaller craters, assuming different populations of impactors, and those different assumptions will tell us where the impactors came from,\u201d Soderblom says. \u201cThis will help to understand the origin of the Late Heavy Bombardment, and whether it was disrupted material from the asteroid belt, or if it was further out.\u201d<\/span><\/p>\n

This research was funded by NASA.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Scientists believe that about 4 billion years ago, during a period called the Late Heavy Bombardment, the moon took a severe beating, as an army of asteroids pelted its surface, carving out craters and opening deep fissures in its crust. Such sustained impacts increased the moon\u2019s porosity, opening up a network of large seams beneath the lunar surface.<\/p>\n","protected":false},"author":2,"featured_media":6174,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-6173","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/09\/MIT-Fractured-Moon_0.jpg",150,100,false]},"author_info":{"info":["RevoScience"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/6173","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=6173"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/6173\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/6174"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=6173"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=6173"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=6173"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}