Search

Impact crater experiments in granular media traditionally involve loosely packed sand targets. However, this study investigates granular impact craters on both loosely and more tightly packed sand targets. We report granular vs. granular experiments that consistently adhere to power-law scaling laws for diameter as a function of impacting energy, similar to those reported by other groups for their experiments utilizing both solid and granular projectiles. In contrast, we observe significant deviations in the depth vs. energy power-law predicted by previous models. To address this discrepancy, we introduce a physical model of uniaxial compression that explains how depth saturates in granular collisions. Furthermore, we present an energy balance alongside this model that aligns well with our crater volume measurements and describes the energy transfer mechanisms acting during crater formation. Central peak formation also plays an essential role in better transferring vertical momentum to horizontal degrees of freedom, resulting in shallow craters on compacted sandbox targets. Our results reveal a depth-to-diameter aspect ratio of approximately $\sim 1/5$, allowing us to interpret the shallowness of planetary craters in light of the uniaxial compression mechanism proposed in this work.

Laboratory made granular-granular impact craters have been used as model analogues of planetary impact craters. These kind of craters have been observed and studied using profilometry techniques that allow to retrieve important morphologic features from the impacted surface. In this work, we propose to use a Time-of-Flight camera (Microsoft Kinect One) for the acquisition of depth data. We show comparisons between the typically used technique and the analysis derived from the Time-of-Flight data. We also release craterslab, a Python library developed to automate most of the tasks from the process of studying impact craters produced by granular projectiles hitting on the surface of granular targets. The library is able to acquire, identify, and measure morphological features of impacted surfaces through the reconstruction of 3D topographic maps. Our results show that using a Time-of-Flight camera and automating the data processing with a software library for the systematic study of impact craters can produce very accurate results while reducing the time spent on different stages of the process.

The study of trajectories is often a core task in several research fields. In environmental modelling, trajectories are crucial to study fluid pollution, animal migrations, oil slick patterns or land movements. In this contribution, we address the lack of standardization and integration existing in current approaches to handle trajectory data. Within this scenario, challenges extend from the extraction of a trajectory from raw sensor data to the application of mathematical tools for modeling or making inferences about populations and their environments. This work introduces a generic framework that addresses the problem as a whole, i.e., a software library to handle trajectory data. It contains a robust tracking module aiming at making data acquisition handy, artificial generation of trajectories powered by different stochastic models to aid comparisons among experimental and theoretical data, a statistical kit for analyzing patterns in groups of trajectories and other resources to speed up pre-processing of trajectory data. It is worth emphasizing that this library does not make assumptions about the nature of trajectories (e.g., those from GPS), which facilitates its usage across different disciplines. We validate the software by reproducing key results when modelling dynamical systems related to environmental modelling applications. An example script to facilitate reproduction is presented for each case.

The precise and continuous tracking of millimetric-sized walkers --such as ants-- is quite important in behavioral studies. However, due to technical limitations, most studies concentrate on trajectories within arenas no more than 100 times bigger than the size of the walker or longer trajectories at the expense of either accuracy or continuity. Our work describes a scientific instrument designed to push the boundaries of precise and continuous motion analysis up to 1000 body lengths or more. It consists of a mobile robotic platform that uses Digital Image Processing techniques to track the targets in real time by calculating their spatial position. During the experiments, all the images are stored, and afterwards processed to estimate with higher precision the path traced by the walkers. Some preliminary results achieved using the proposed tracking system are presented.

We introduce an instrument for a wide spectrum of experiments on gravities other than our planet's. It is based on a large Atwood machine where one of the loads is a bucket equipped with a single board computer and different sensors. The computer is able to detect the falling (or rising) and then the stabilization of the effective gravity and to trigger actuators depending on the experiment. Gravities within the range 0.4 g to 1.2 g are easily achieved with acceleration noise of the order of 0.01 g. Under Martian gravity we are able to perform experiments of approximately 1.5 seconds duration. The system includes features such as WiFi and a web interface with tools for the setup, monitor and the data analysis of the experiment. We briefly show a case study in testing the performance of a model Mars rover wheel in low gravities., Comment: 3 pages, 4 figures