Importance of Asteroids Science Origin of the Solar System - PowerPoint PPT Presentation

Importance of Asteroids Science • Origin of the Solar System Resources • Metals, ice Impact mitigation • Deflection https://solarsystem.nasa.gov/planets/ceres

Asteroid structure From Walker et al 2006

Seismic Geophysics http://geologylearn.blogspot.com.au/2015/06/marine ‐ and ‐ land ‐ seismic ‐ aquisition.html

Seismic Geophysics Active vs passive source What can we determine through seismic? 1. Seismic velocity (P ‐ and S ‐ wave) • From this and other data, we can infer strength and other properties • Fracture presence and orientation 2. Imaging (requires a lot of source and receiver locations)

Seismic Geophysics http://epic.awi.de/35606/

Seismic Sources & Receivers http://www.kgs.ku.edu/Publications/PIC/pic37.html http://www.kgs.ku.edu/Publications/PIC/pic37.html http://www.hohoilfieldservices.co.uk/industry ‐ seismic.php

Seismic sources and receivers From Bagaini et al 2010

Planetary Seismic Missions • Moon Apollo 17’s Lunar Seismic Profiling Experiment (LSPE) http://www.dlr.de/pf/en/desktopdefault.aspx/tabid ‐ 8635/

Planetary Seismic Missions Seismic wave travel times vs distance between source and receiver. From Kovach et al 1973.

Planetary Seismic Missions • Moon • Mars • Venus Apollo 17’s Lunar Seismic Profiling Experiment (LSPE) http://www.dlr.de/pf/en/desktopdefault.aspx/tabid ‐ 8635/

Planetary Seismic Missions • Moon • Mars • Venus • Future: InSIGHT – will place a seismic receiver station on Mars https://www.nasa.gov/press ‐ release/nasa ‐ suspends ‐ 2016 ‐ launch ‐ of ‐ insight ‐ mission ‐ to ‐ mars

Asteroid Missions • Deep Space 1 • Hayabusa 1 & 2 • Rosetta • AIM DART • ARM http://sci.esa.int/rosetta/14615 ‐ comet ‐ 67p/

Asteroid Seismic Geophysics From Walker and Huebner 2004

Value of Asteroid Seismic Geophysics • What can we determine through seismic on an asteroid that is useful? • Structure • Strength/rippability • Layering and internal features • Composition… not so much

Challenges • Limited mass (sources and receivers, input energy, bandwidth of returned data) • Low gravity (potentially difficult anchoring) • No atmosphere • Unknown environment • Accurate digital elevation model required for quality imaging • Perturbation of environment during measurement • Attenuation and scattering of seismic signal

Emplacement of Seismic Tools • Traditional anchoring, e.g. harpoons (67P) • Releasing a hardening fluid • Penetrators

Emplacement of Seismic Tools The Lunar Net penetrator design. From Smith et al (2012).

Emplacement of Seismic Tools DS2 penetrator schematic in ground. From Lorenz et al 2000.

Emplacement of Seismic Tools • Traditional anchoring, e.g. harpoons (67P) • Releasing a hardening fluid • Penetrators • Covering an asteroid with single use receivers and using an impact source • Laser receiver • More exotic designs – solar sail, ion thrusters

Open Questions • What are the effects of an asteroid environment (gravity, atmosphere, temperature etc) and how do they impact seismic measurement, if at all? • Is there a correlation between surface and subsurface/geomechanical properties of asteroids? • Can we develop relationships between relevant parameters and seismic data so we can predict the outcome of seismic exploration on asteroids?

Acknowledgements Simit Raval Andrew Dempster Serkan Saydam Robert Anderson

References First image credit: https://www.space.com/11093 ‐ photos ‐ asteroids ‐ deep ‐ space ‐ rocks.html Walker et al 2006, A preliminary analysis of seismological techniques to study Eros and other asteroids, Adv. in Space Res. , 37, 142 ‐ 152. Bagaini et al 2010, Land seismic techniques for high ‐ quality data, Oilfield Review , 22, 28 ‐ 39. Kovach et al 1973, The structure of the lunar crust at the Apollo 17 site, Proc. of the Fourth Lunar Sci. Conf. , 3, 2549 ‐ 2560. Walker and Huebner 2004, Seismological investigation of asteroid and comet interiors, in: Mitigation of Hazardous Asteroids and Comets, Cambridge University Press, Cambridge. Smith et al 2012, Lunar Net – a proposal in response to an ESA M3 call in 2010 for a medium sized mission, Exp. Astron. , 33, 587 ‐ 644. Lorenz et al 2000, Penetration tests on the DS ‐ 2 Mars microprobes: penetration depth and impact accelerometry, Plan. & Space Sci. , 48, 419 ‐ 436.