{"id":8474,"date":"2022-07-08T00:52:04","date_gmt":"2022-07-08T04:52:04","guid":{"rendered":"https:\/\/spaceandplanetarynewswire.com\/?p=8474"},"modified":"2022-07-08T00:52:04","modified_gmt":"2022-07-08T04:52:04","slug":"swri-led-study-provides-new-insights-about-surface-structure-of-asteroid-bennu","status":"publish","type":"post","link":"https:\/\/spaceandplanetarynewswire.com\/?p=8474","title":{"rendered":"SwRI-Led Study Provides New Insights About Surface, Structure of Asteroid Bennu"},"content":{"rendered":"
A recent SwRI-led study provided new insights into the surface and structure of asteroid Bennu. NASA\u2019s OSIRIS-REx spacecraft data indicate nearly twice the void space near its surface in comparison to the overall body. Courtesy of NASA\/Goddard\/University of Arizona<\/figcaption><\/figure>\n

When NASA\u2019s OSIRIS-REx spacecraft collected samples from asteroid Bennu\u2019s surface in 2020, forces measured during the interaction provided scientists with a direct test of the poorly understood near-subsurface physical properties of rubble-pile asteroids. Now, a Southwest Research Institute-led study has characterized the layer just below the asteroid\u2019s surface as composed of weakly bound rock fragments containing twice the void space as the overall asteroid.<\/p>\n

\u201cThe low gravity of rubble-pile asteroids such as Bennu weakens its near-subsurface by not compressing the upper layers, minimizing the influence of particle cohesion,\u201d said SwRI\u2019s Dr. Kevin Walsh, lead author of a paper<\/a> about this research published in the journal Science Advances<\/em>. \u201cWe conclude that a low density, weakly bound subsurface layer should be a global property of Bennu, not just localized to the contact point.\u201d<\/p>\n

Fitting its designation as a \u201crubble-pile asteroid,\u201d Bennu is a spheroidal collection of rock fragments and debris 1,700 feet in diameter and held together by gravity. It is thought to have been formed after a collision involving a larger main-asteroid-belt object. Rocks are scattered across its heavily cratered surface, indicating that it has had a rough-and-tumble existence since being liberated from its much larger parent asteroid some millions or billions of years ago.<\/p>\n

<\/p>\n

The goal of OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security\u2013Regolith Explorer) mission is to collect and return at least 60 grams of surface material from Bennu and deliver it to Earth in 2023. Sample collection activities provided additional insights.<\/p>\n

According to Walsh, researchers involved in the OSIRIS-REx mission have so far measured Bennu\u2019s thermal properties and craters to estimate the strength and porosity of discrete particles of rubble-pile asteroids. The ensemble of particles, or regolith, at an asteroid\u2019s surface controlling and influencing long-term evolution have not yet been probed directly until now.<\/p>\n

Before, during, and after the sampling event, the Sample Acquisition Verification Camera (SamCam) of the OSIRIS-REx Camera Suite captured images looking at the Touch-and-Go Sample Acquisition Mechanism (TAGSAM) robotic arm.<\/p>\n

A SwRI-led study found that the rocky fragments dominating the surface asteroid Bennu are weakly bound, exhibiting near-zero cohesion, probably due to size and low gravity of the small body. Courtesy of NASA\/Goddard\/University of Arizona<\/figcaption><\/figure>\n

\u201cThe SamCam images bracketing the moment of contact show the contact caused considerable disturbance at the sample site,\u201d said Dr. Ron Ballouz, a co-author from Johns Hopkins University\u2019s Applied Physics Laboratory. \u201cNearly every visible particle is moved or re-oriented at all points along the circumference of TAGSAM up to a 15-inch radius.\u201d<\/p>\n

These SamCam images showed the downward force of TAGSAM lifted a nearly 16-inch rock. Though strong enough to withstand breaking, the rock was re-oriented and small debris lofted off its surface. The mobility of these millimeter-scale particles under relatively weak forces suggests minimal cohesive bonding with the surface of the larger rock.<\/p>\n

Scientists have theorized that the average regolith particle size increases as asteroid size decreases, because larger bodies retain smaller materials due to a higher surface gravity. The team then compared Bennu to similar rubble-pile asteroids.<\/p>\n

\u201cWe discovered a dichotomy between the rough, boulder-covered surfaces of Bennu and Ryugu versus Itokawa, which includes ponds of smaller particles across 20% of its surface,\u201d Walsh said. \u201cThis could have several explanations, including that the latter\u2019s near-surface has compressed enough to frustrate these microparticles percolating into the interior or perhaps the granular deposits are subsurface layers revealed by a recent disruptive reorganization of the body.\u201d<\/p>\n

A companion paper in the journal Science and co-authored by Walsh characterized the 30-foot-long elliptical crater excavated by the TAGSAM arm when it collected the sample. The event mobilized rocks and dust into a debris plume, exposing material that is darker, redder and more abundant in fine particulates than the original surface. The displaced subsurface material\u2019s bulk density is about half that of the asteroid as a whole.<\/p>\n","protected":false},"excerpt":{"rendered":"

When NASA\u2019s OSIRIS-REx spacecraft collected samples from asteroid Bennu\u2019s surface in 2020, forces measured during the interaction provided scientists with a direct test of the poorly understood near-subsurface physical properties of rubble-pile asteroids. Now, a Southwest Research Institute-led study has characterized the layer just below the asteroid\u2019s surface as composed of weakly bound rock fragments…<\/p>\n","protected":false},"author":71,"featured_media":8477,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"fifu_image_url":"https:\/\/www.swri.org\/sites\/default\/files\/styles\/facebook_image\/public\/media-resources\/asteroid-bennu.jpg?itok=F0M7T13M","fifu_image_alt":"SwRI-Led Study Provides New Insights About Surface, Structure of Asteroid Bennu","footnotes":""},"categories":[207],"tags":[],"class_list":["post-8474","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"_links":{"self":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/8474","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/users\/71"}],"replies":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=8474"}],"version-history":[{"count":1,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/8474\/revisions"}],"predecessor-version":[{"id":8476,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/8474\/revisions\/8476"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/media\/8477"}],"wp:attachment":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8474"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8474"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8474"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}