The surfaces of many planetary bodies, including asteroids, moons, and planets, are composed of rubble-like grains held together by varying levels of gravitational attraction and cohesive forces. Future instrumentation for operation on, and interacting with, such surfaces will require efficient and effective design principles and methods of testing. Here we present results from the EMPANADA experiment (Ejecta-Minimizing Protocols for Applications Needing Anchoring or Digging on Asteroids) which flew on several reduced gravity parabolic flights. EMPANADA studies the effects of the insertion of a flexible probe into a granular medium as a function of ambient gravity. This is done for an idealized 2D system as well as a more realistic 3D sample. To quantify the dynamics inside the 2D granular material we employ photoelasticity to identify the grain-scale forces throughout the system, while in 3D experiments we use simulated regolith. Experiments were conducted at three different levels of gravity: martian, lunar, and microgravity. In this work, we demonstrate that the photoelastic technique provides results that complement traditional load cell measurements in the 2D sample, and show that the idealized system exhibits similar behaviour to the more realistic 3D sample. We note that the presence of discrete, stick-slip failure events depends on the gravitational acceleration.

Probing regolith-covered surfaces in low gravity

We present a newly developed experiment for the examination of low-speed impacts under asteroidconditions. More specifically, our experimental setup enables us to simulate a very clean milligravity environ-ment under vacuum, in which projectiles are shot at a granular bed at several cm/s. This granular bed consists ofirregularly formed basalt particles with different size distributions. The experiment is carried out in the Bremendrop tower in its catapult mode, granting more than 9 s microgravity. Here, we discuss the setup and assess itsperformance.

Experiments on rebounding slow impacts under asteroid condition

Q&A session 1

**Session Chairs:**
<br>
<br>Alejandra Aguirre and Luis Pugnaloni

technical paper

[EPJ Web of Conferences, Volume 249 (2021)](https://www.epj-conferences.org/articles/epjconf/abs/2021/03/contents/contents.html)

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**Meet the Organizers**

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Welcome to the 2021 Powders and Grains conference. Please review the event's **Code of Conduct** [here](https://drive.google.com/file/d/1P_bOrjI2jSE55twRPVzWl5VkfARR-qBL/view?usp=sharing). 


**Powders & Grains 2021 Walkthrough Screencast**

This video will demonstrate how to navigate the conference and virtual platform -- and network with other attendees and speakers.


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Powders & Grains 2021

Powders & Grains 2021 will be held in Buenos Aires (Argentina, VIRTUAL) July 5, 13, 21, 29 and Aug 6, 2021. The aim of the conference is to give an up-to-date picture of the broad research field of granular media, powders and grains. Contributions from experts around the world will focus on research topics that cover a wide range of open problems in the field.

Jonathan Kollmer

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9

SHORT BIO

Presentations

Probing regolith-covered surfaces in low gravity

Experiments on rebounding slow impacts under asteroid condition

Q&A session 1

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