Laboratory Astrophysics in granular systems
We have been doing laboratory experiments on granular systems, with applications to asteroids.
Three papers form Esteban's thesis. We looked at size segragation caused by impact excited ejecta
and ricochets of glass marbles on sand. We have also studied
pulse propagation in granular media using a 7 channel accelerometer array.
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On oblique impacts (led by Bingcheng). Subsurface pulses are strongly (x5) asymmetric even when
the resulting crater is round.
Subsurface pulse, crater and ejecta asymmetry from oblique impacts into granular media (on arxiv) ,
ADS/Icarus
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Surface motions associated with a normal impact outside the crater and before the ejecta curtain lands are tracked using PIV and cross correlation in high speed videos. Surface particle motions excited by a low velocity normal impact into a granular medium (arxiv) ,
in Icarus
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Propagation and attenuation of pulses driven by low velocity normal impacts in granular media.
With Max, Lucas and Bingcheng! We carry out experiments of impacts
into granular media (a washtub of millet) using a 7 channel accelerometer array.
Attenuation is rapid.
We use a diffusive approximation to predict how the signal strength decays as a function
of pulse propagation distance and we make some predictions for the DART mission.
on arxiv ,
In Icarus
- Esteban's thesis: Ricochets on Asteroids. We carry out lab experiments of low velocity grazing
impacts of marbles into sand. A scaling argument suggests that most low velocity impacts
(near escape velocity)
on asteroids will ricochet or roll across the surface.
Ricochets on Asteroids: Experimental study of low velocity grazing im
pacts into granular media (arxiv),
In Icarus ,
UR newscenter ,
Esteban's movies
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Esteban's thesis:
Ricochets on Asteroids II.
We explore the regime between ballistic impact
and impacts into fine sand to understand how low velocity impacts depend on grain size.
Ricochets on Asteroids II: Sensitivity of laboratory experiments of low velocity grazing impacts on substrate grain size ,
In Icarus
- Esteban's thesis: We did lab experiments in gravel to explore mechanisms for stranding
boulders on rubble asteroids: A single pressure pulse from below can eject particles from a granular medium up off the
surface, leaving initially burried boulders stranded on the surface afterward.
On an asteroid such a seismic pulse could be caused by an energetic meteor impact.
This gives a different mechanism accounting for large boulders on the surfaces of
rubble asteroids such as Ryugu and Bennu.
arxiv,
Boulder Stranding in Ejecta Launched by an Impact Generated Seismic Pulse (Icarus)
Movies showing our lab experiments of impacts into bowls of gravel.
experiment 42 high speed video ,
experiment 42 regular speed ,
Experiment 41 high speed ,
Experiment 41 regular speed