Measuring the bulk density of meteorites nondestructively using three‐dimensional laser imaging

Abstract

[1] The fragile and unique nature of meteoritic material requires a method of density measurement that is accurate yet nondestructive. This is difficult to achieve using conventional methods. In this study, the bulk density of eleven meteorite fragments which vary in shape, size, surface roughness, porosity, and reflectance has been determined using three-dimensional (3-D) laser imaging. An auto-synchronized laser camera raster scanned the surface features of each meteorite without contact and to a high degree of precision. Visualization software was used to align several scans into a closed model and to compute its volume. The mass having been predetermined, the density was then easily computed. Three-dimensional laser imaging is the least invasive method of density measurement currently in use. The precision of the approach is less than 1%. The densities determined using 3-D laser imaging compare very well with previously published values, based on a variety of different measurement techniques. The average difference is 3.4% and can be attributed to the presence of heterogeneities and to the limited amount of comparative data available. For nine out of the eleven samples studied, the densities determined using 3-D laser imaging are higher than previously published results. Friction between fluid and container, and bead compaction might have led to an overestimation of the volume measured using Archimedean methods. In addition to volume measurements, 3-D images of rock samples can yield detailed information on surface properties from a distance. The technique could be used for semiautonomous planetary geological exploration.

Determination of bulk density for small meteorite fragments via visible light 3‐D laser imaging

“…In this work, bulk densities for eleven hand sample size fragments from seven meteorites, ranging in mass from 754 to 32 g, were measured. On average, the densities obtained using 3‐D laser imaging were 3.4% higher than published densities from the literature (Smith et al. 2006).…”

“…The vertical error bars are the interoperator coefficients of variation from Table 3. Open triangles are laser imaging densities from the 11 fragments of seven meteorites reported in Smith et al. (2006).…”

“…Reflection intensity, I , is also recorded, providing albedo information about the target’s surface. The Laser Metrology System offers several advantages over previous infrared laser cameras (e.g., Smith et al. 2006), in that it uses a shorter wavelength visible light laser for finer resolution measurements as well as variable focusing and laser power, allowing for more flexibility in the choice of scanning parameters.…”

“…A selection of edited point clouds were aligned and assembled into a closed 3‐D volumetric model of each fragment using an industrial metrology software package (PolyWorks; InnovMetric, Quebec City, Canada), using procedures similar to those described by Smith et al. (2006).…”

“…Smith et al. (2006) introduced a nondestructive method for obtaining meteorite volumes using infrared three‐dimensional (3‐D) laser imaging.…”