Size and Density Estimation From Impact Track Morphology in Silica Aerogel: Application to Dust From Comet 81p/Wild 2

Penetration into low-density media: In situ observation of penetration process of various projectiles

“…(4) indicates that R m /R p does not depend directly on q t and q p . This seems consistent with some experimental results (e.g., Ishibashi et al, 1990;Niimi et al, 2012). The precise dependence on q t and/or q p should be investigated by the accurate evaluation of both P(R p , 0) and P cs (e.g., the evaluation of P(R p , 0) by an impedance matching solution between the Hugoniot curves of the projectiles and aerogels, and the dependence of P cs on aerogel density as indicated by Domín-guez et al (2004)).…”

“…For more quantitative description, the depth L and the maximum diameter D m of final tracks are often measured as a function of the parameters varied in the experiments such as, projectile density q p , projectile diameter D p (radius R p ), projectile and target strengths, target density q t , and impact velocity v 0 . The features about L/D p and D m suggested by previous various experiments with low-density targets are roughly summarized as follows: L/D p increases with v 0 , and takes a peak, then decreases (e.g., Fechtig et al, 1980;Werle et al, 1981;Ishibashi et al, 1990;Tsou, 1990; Barrett et al, 1992;Kitazawa et al, 1999;Burchell et al, 2001;Hörz et al, 2009), and is scaled by q p /q t (e.g., Barrett et al, 1992;Hörz et al, 1993;Love et al, 1993;Burchell et al, 1999Burchell et al, , 2009Niimi et al, 2011Niimi et al, , 2012, and D m is proportional to D p regardless of q p /q t and proportional to v 0 (e.g., Ishibashi et al, 1990;Kitazawa et al, 1999;Burchell et al, 2008;Niimi et al, 2012).…”

“…Hypervelocity impact experiments on very low-density materials have been carried out to extend the cratering experiments (e.g., Cannon and Turner, 1967;Fechtig et al, 1980;Werle et al, 1981;Love et al, 1993;Trucano and Grady, 1995) and to develop and calibrate the instruments for intact capture of interplanetary dust samples using foams (e.g., Ishibashi et al, 1990;Tsou, 1990) and for aerogels (e.g., Barrett et al, 1992;Hörz et al, 1993Hörz et al, , 1998Hörz et al, , 2009Burchell et al, 1999Burchell et al, , 2001Burchell et al, , 2008Burchell et al, , 2009Kitazawa et al, 1999;Niimi et al, 2011Niimi et al, , 2012. These previous studies indicate that the impacts between high-density projectiles and low-density targets generate ''penetration tracks'': track diameter is small at the entrance (= impact point), then increases with depth, takes a peak, and decreases (this qualitative feature is common for any track).…”

Impact experiments of exotic dust grain capture by highly porous primitive bodies

“…4 shows the relationshi p between the MW/PD ratio and the initial dynamic pressure, normalized by the projectile's tensile strength. We also plotted the results of various projectile s into aerogel, as obtained in previous studies (Burchell et al, 2008;Hörz et al, 2009;Kearsley et al, 2012;Niimi et al, 2012), using the tensile strength of soda-lime glass, copper (60 MPa, 195 MPa, respectively;Kaye and Laby, 1986 ), alumina (258 MPa;Shackelford and Alexander , 2000 ), carbonaceous chondrite meteorit es (637, 614, 614 MPa for Allende, Murchison, Orgueil, respectively ; Tsuchiya ma et al, private communicati on, 2012), and graphite (10.9 MPa; Manhani et al, 2007 ). The MW/ PD ratio increases with increasing dynamic pressure.…”

Herscheland IRAM-30 m observations of comet C/2012 S1 (ISON) at 4.5 AU from the Sun

“…The sizedependent grain velocities v d (a), as well as the maximum grain radius a max , are computed following Crifo & Rodionov (1997). We assume a nucleus and dust density of 500 kg m −3 (Thomas et al 2013;Davidsson et al 2007;Richardson et al 2007;Niimi et al 2012). Both the maximum grain size and dust velocities critically depend on the nucleus size and the gas production rate at the surface, which are both poorly constrained.…”