¹M. J. Burchell,²R. C. Ogliore,¹P. J. Wozniakiewicz
Meteoritics & Planetary Sciences (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70090]
¹Centre for Astrophysics and Planetary Science, School of Engineering, Mathematics and Physics
²University of Kent,Canterbury, Kent, UK2 Department of Physics, University of Central Florida, Orlando, Florida, USA
Published by arrangement with John Wiley & Sons

The desire to sample material from the interior of Io, by flying through its volcanicplumes, requires consideration of the flyby speed and the types of sample collection techniquesthat can be utilized. Low speed collection (1–2.5 km s1) would require an orbit around Io itself,which is unlikely due to the accumulated radiation dose that would be experienced. Moderatecollection speeds (7–9 km s1) are possible for flybys of Io arising from either a single passagethrough the Jovian system (followed by sample return) or a carefully selected orbit aroundJupiter that has the main purpose of visiting Io. However, even if they include an Io closepassage, most Jovian mission orbit concepts also include and even prioritize other scienceobjectives, resulting in orbits with Io collection speeds of around 17–19 km s1 (or greater).Depending on the speed and collector material, the peak shock pressures during collection maythus range from 5 to hundreds of GPa for impacts on solid, nonporous media, with pressuresfrom 0.01 to 5 GPa for impacts on low-density aerogels. These shock pressures are calculatedherein for a range of Io encounter speeds and collector types, and the degree of sample captureand impact processing are estimated. While capture of material is shown to be possible at speedsup to 10 km s1, permitting both in situ analysis or sample return to Earth, above these speedsretention of significant amounts of unvaporized material in a collector is not viable.

^1,2Birger Schmitz,³Yue Cai,^2.4Shiyong Liao,⁵Victoriano Pujalte,³Ting Ruan,⁶Robert P. Speijer,^7,8Ellen Thomas
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70082]
¹Astrogeobiology Laboratory, Department of Physics, Lund University, Lund, Sweden
²Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
³State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Chinese Academy ofSciences, Nanjing, China
⁴Chinese Academy of Sciences, Center for Excellence in Comparative Planetology, Hefei, China
⁵Department of Geology, Faculty of Science and Technology, University of the Basque Country, Bilbao, Spain
⁶Department of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium
⁷Department of Earth and Planetary Sciences, Yale University, New Haven, CT, USA
⁸Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT, USA
Published by arrangement with John Wiley & Sons

Almost 10 years have passed since microtektites and microkrystites were reportedfor the Paleocene–Eocene (P–E) boundary in drill cores and outcrop in New Jersey and inODP Hole 1051B in the western North Atlantic. The glassy spherules were interpreted toreflect an impact trigger for the Paleocene–Eocene Thermal Maximum (PETM). Since then,many detailed studies of sediment strata across the P–E boundary worldwide have beenperformed, but so far, no additional reports of impact spherules have been published.Negative results usually are not published, but here we report a lack of success in finding suchspherules at the P–E boundary in ODP Hole 1051B. We searched 90 g of sediment from thesame interval in the same core from which 56 impact spherules >63 lm were previouslyreported from 35 g of sediment, but did not find microtektites or microkrystites. We also didnot find impact spherules in a detailed search of 2.3 kg of sediment from the P–E boundary inthe Zumaia section (Spain), where the boundary is marked by a minor iridium anomaly. Inaddition, we did not find such spherules in P–E boundary sediment from sections in Europeand the Middle East nor in drill cores from the southern Atlantic. We urge the researchcommunity to report further both negative and positive results on this issue in order toelucidate the envisioned P–E boundary impact event.