LINK<\/strong><\/a><\/p>\n\n\n\n“Highlights<\/p>\n\n\n\n
\u2022 The OSIRIS-REx sampling system will mobilize regolith particles on asteroid Bennu.
\u2022 Mobilized particles will re-accrete, escape, or temporarily orbit Bennu.
\u2022 Particles will re-accrete globally but will be concentrated around the sample site.
\u2022 Gravity and cohesion lead to mobility for a preferred particle size of tens of cm.”<\/p>\n\n\n\n
“The Origins, Spectral Interpretation, Resource Identification, and Security\u2013Regolith Explorer (OSIRIS-REx) mission will collect material from the asteroid Bennu and return it to Earth. The sample collection method uses pressurized nitrogen gas to mobilize regolith. It is likely that the gas will mobilize more, potentially much more, material than is captured by the Touch-and-Go Sample Acquisition Mechanism (TAGSAM) for return. The amount, velocities, and fate of this mobilized material have important implications for our understanding of Bennu’s physical properties and processes, such as impact cratering, regolith mobility, and the recently observed natural ejection of particles. The nature of the TAGSAM-ejected material is also significant for mission operations. We conducted numerical simulations and ground-based tests to estimate the amount and speeds of material mobilized by the sampling event. The estimated ejected masses range from 12\u202fkg to >165\u202fkg; given that Bennu appears to be a nearly strengthless rubble pile, the higher end of the mass range is more likely. Maximum ejection speeds for 1-cm-diameter particles could reach 10\u202fm\/s; smaller particles will be ejected at faster speeds. Minimum ejection speeds will be determined by the as yet unknown cohesive strength of Bennu’s regolith. Material ejected more slowly than 10\u202fcm\/s will reaccrete on Bennu; material ejected between 10 and 30\u202fcm\/s may or may not reaccrete; and material ejected faster than 30\u202fcm\/s will escape. Some of the ejected material is predicted to remain in transient orbits around Bennu. The lifetimes of these orbits span from days to several weeks, the maximum duration of our integrations. Reaccreted material should be concentrated in a region near the sample site, although re-impacts will occur globally. Gas from TAGSAM will mobilize material beyond the contact perimeter; because of interactions between cohesion and microgravity, there is a preferred particle size of mobility, predicted to be tens of centimeters, depending on the TAG latitude. Observing Bennu during and after the sampling event will make it possible to test these predictions and understand how the asteroid responds to disruption and particle mobility across the surface.”<\/p>\n","protected":false},"excerpt":{"rendered":"
E.B. Bierhaus, J.T. Songer, B.C. Clark, R.D. Dubisher, S.L. Deden, K.S. Payne, D. Wurts, J.W. McMahon, B.Rozitis, D.S.Lauretta IcarusIn Press, Journal Pre-proof, Available online 5 October 2020 LINK “Highlights \u2022 The OSIRIS-REx sampling system will…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77,552,181,1184],"tags":[5719,263,1886,4899,270],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/25087"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=25087"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/25087\/revisions"}],"predecessor-version":[{"id":25088,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/25087\/revisions\/25088"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=25087"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=25087"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=25087"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}