Lunar & Planetary Science Conference: March 2000[TPSAVC Site map]

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 Conference details

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The following is a very limited selection of abstracts that happen to interest me!

Housen K. R. * Holsapple K. A.
Numerical Simulations of Impact Cratering in Porous Materials [#1498]
Numerical simulations are conducted to model the formation of impact craters in highly porous materials.
Detailed comparisons with numerous cratering experiments are made to develop a model of the unusual
mechanics of cratering on porous asteroids.

Shrine N. R. G. * Burchell M. J. Grey I. D. S.
Velocity Scaling of Impact Craters in Water Ice with Relevance to Cratering on Icy Planetary Surfaces [#1696]
1 mm diameter aluminium spheres were fired at ice targets at velocities of 1-7.3 km/s to determine the
velocity dependence of ice impact cratering. The scaling of crater dimensions with impact energy is
compared to previous lower velocity data.

Asphaug E. *
The Large, Undisturbed Craters of Mathilde: Evidence for Structural Porosity [#1864]
The impact craters on Mathilde are curious in lacking associated ejecta deposits and disruption.
Detailed models show that Mathilde’s porosity both isolates the shock and enhances ejection speed beyond

Leinhardt Z. M. * Richardson D. C. Quinn T.
When Rubble Piles Collide [#1274]
We present results from a project using a direct numerical method to map the parameter space of
collisions between km-sized spherical rubble piles. We find that our rubble piles are relatively easy to
disperse, even at low impact speed.

Bottke W. F. * Morbidelli A. Petit J. M. Gladman B. Jedicke R.
Tracking NEAs from Their Source Regions to Their Observed Orbits [#1634]
We use our estimate of the debiased NEA population and results from numerical integration to determine
the inflow/outflow rate of NEAs from their source regions and the asteroid populations in those regions.

Warner M. * Morgan J.
3D Seismic Velocity Structure of the Chicxulub Impact Crater [#1674]
3D seismic velocity tomography over the Chicxulub impact crater reveals size and shape of central
uplift, constrains melt-sheet thickness & shows minimal Moho uplift at the crater center.

Collins G. S. * Melosh H. J. Morgan J. V. Warner M. R.
Hydrocode Simulations of Chicxulub Crater Collapse [#1733]
We have simulated the collapse stage of the Chicxulub crater’s development and compared our results with
those of the Chicxulub Seismic Experiment in order to answer the enigmatic question of how the intricate
structures that characterize complex craters are formed.

Pilkington M. Hildebrand A. R. *
Three-dimensional Magnetic Imaging of the Chicxulub Crater [#1190]
Three-dimensional inversion of the magnetic field data over the Chicxulub crater using a two-layer model
reveal an upper ~45 km radius zone of <5 km-wide anomalies with concentric structure (melt sheet
alteration) and a lower ~40-km diameter central high (central uplift).

Pope K. O. * Ocampo A. C.
Chicxulub High-Altitude Ballistic Ejecta from Central Belize [#1419]
Chicxulub ejecta are found in central Belize, 475 km southeast of the impact crater center. These
deposits are ballistic ejecta launched along high-altitude trajectories above the atmosphere and deposited as a
discontinuous sheet on the terminal Cretaceous land surface.

Dypvik H. * Kyte F. T. Smelror M.
Iridium Peaks and Algal Blooms — The Mjølnir Impact [#1538]
Iridium peaks and algal blooms are related to the late Jurassic Mjølnir impact. They reflect the
environmental influences of the impact, with the disaster species Prasinophytae blooming after the impact, but
before deposition of the fireball layer.

Reimold W. U. * Armstrong R. A. Koeberl C.
New Results from the Deep Borehole at Morokweng, North West Province, South Africa: Constraints on the
Size of this J/K Boundary Age Impact Structure [#1074]
The Morokweng impact structure of >340-70 km diameter was formed at 145±2 Ma, the age of the J/K
boundary. A 3.4 km drillcore from 40 km off the center of Morokweng has been studied. The results indicate
an original diameter of 75-80 km.

Artemieva N. A. Shuvalov V. V.
Model of Disrupted Meteoroid Passage Through Planetary Atmosphere [#1543]
3D modeling of separate fragments motion is conducted to define drag, lift and heat transfer coefficients. The
results are used in a set of meteor physics equations for real events on the Earth and possible impacts on Mars
and Venus.

Shuvalov V. V.
Radiation Impulse of Chicxulub Impact [#1568]
Numerical simulations of all stages of Chicxulub impact including a flight through the atmosphere,
cratering and plume rising were used to calculate radiation impulse on the Earth’s surface and to estimate an
area of wildfires origin.

Wichman R. W.
Volcanically Modified Impact Craters (Part 2): Where on Earth Could They Be? [#1943]
Varied magmatic & sedimentation rates should affect the likelihood of impact volcanism. Mid-ocean ridges are
likely sites; magmatic arcs, unlikely. Continental rifts may be the best sites for preservation on land.

Croskell M. S.
Mechanisms Involved in the Formation of the Cretaceous-Tertiary Boundary Layer [#2084]
The fundamental processes involved in the production of the K/T boundary layer are detailed in light of
the geological idiosyncracies which they help to explain.

Flynn G. J. * Keller L. P. Jacobsen C. Wirick S. Miller M. A.
Interplanetary Dust Particles as a Source of Pre-Biotic Organic Matter on the Earth [#1409]
Entry heating modeling shows IDPs from 5 to 25 microns in size contribute the bulk of the exogenous
organic matter to Earth. We measured the organic content of IDPs in this size range by infrared and by x-ray
absorption spectroscopy at the C-edge.

Lucey P. G. *
Lunar Astrobiology [#1492]
The lunar poles may be an environment conducive to pre-biotic chemistry. Production of organics from
inorganic precursors requires source material, energy, and proper environmental conditions. The lunar
poles may have all three.

Pierazzo E. * Chyba C. F.
Impact Delivery of Organics to Europa [#1656]
Hydrocode simulations of cometary impacts on the surface of Europa suggest that, even though a large
fraction of the projectile escapes Europa’s gravity, a non-negligible amount of some amino acids would
survive and be retained on Europa.

Mastrapa R. M. E. Glanzberg H. * Head J. N. Melosh H. J. Nicholson W. L.
Survival of Bacillus Subtilis Spores and Deinococcus Radiodurans Cells Exposed to the Extreme Acceleration
and Shock Predicted During Planetary Ejection [#2045]
To determine the survivability of ejection from a planet, two uv-resistant spores have been tested for
resistance to high acceleration and high change in acceleration, or jerk.

Toporski J. K. W. * Steele A. Westall F. Griffin C. Whitby C. Avci R. McKay D. S.
Electron Microscopy Studies, Surface Analysis and Microbial Culturing Experiments on a Depth Profile
Through Martian Meteorite Nakhla [#1636]
Combined electron microscopy studies and culturing experiments have shown that Nakhla became
contaminated with recent terrestrial microorganisms. Additional surface analysis detected an as yet unknown
organic species which may represent a biomarker.

Wynn-Williams D. D. * Edwards H. G. M. Newton E. M.
Raman Spectroscopy of Microhabitats and Microbial Communities: Antarctic Deserts and Mars
Analogues [#1015]
Raman spectroscopic studies of functional biomolecules in Antarctic lithic communities (Mars analogues)
have identified several key biomarkers. This is proposed as an eminently suitable technique for the
detection of extinct or extant life on Mars.

Allen C. C. * Albert F. G. Chafetz H. S. Combie J. Graham C. R. Kieft T. L. Kivett S. J. McKay D. S.
Steele A. Taunton A. E. Taylor M. R. Thomas-Keprta K. L. Westall F.
The Search for Signs of Ancient Martian Microbes: Physical Biomarkers in Carbonate Thermal
Springs [#1257]
If Mars ever supported microbial life, signatures of biogenic activity (biomarkers) could prove critical
to its identification. Carbonate thermal springs yield a variety of physical biomarkers — prime
evidence in the search for past or present life.

Westall F. * Steele A. Toporski J. Walsh M. M Allen C. C. Guidry S. McKay D. S. Gibson E. K.
Chafetz H. S.
3.8 b.y. History of Bacterial Biofilms and Their Significance in the Search for Extraterrestrial Life [#1707]
Bacterial biofilms are almost ubiquitous in terrestrial environments, many similar to past or present
Martian environments. Together with ToF-SIMS analysis of the in situ organics, fossil biofilms constitute
reliable biomarkers.

Moreau J. W. * Sharp T. G.
Optical and Electron Microscopic Characterization of Precambrian Gunflint Microfossils [#2015]
Precambrian Gunflint microfossils are studied using optical microscopy, FESEM, and TEM. Sub-micron
scale morphological observations and microanalyses are used to characterize the physical and chemical nature
of ancient terrestrial microfossils.

Morris P. A. Wentworth S. J. Thomas-Keprta K. L. Allen C. C. Schwandt C. S. McKay D. S. Bell M. S.
Gibson E. K.
Mineralogy of ~1-10 Micrometer Iron Spheres Within 3.4 Ga Rocks (Towers Formation, Warrawoona Group,
Northwestern Australia) [#2101]
Iron-bearing spherules in Archean Warrawoona rocks are composed of hematite and goethite. They are
clearly syngenetic with the rock but their origin, whether biological or abiogenic, is not yet known.

Walsh M. M. Westall F.
Revisiting the Swaziland Supergroup: New Approaches to Examining Evidence for Early Life on Earth [#1932]
The re-examination by SEM of 3.4 Ga fossiliferous carbonaceous cherts reveals fungal contaminants in
addition to indigenous microfossils. Weathered volcanic flows associated with fossiliferous chert layers
offer a promising area for further study of early life on Earth.

Nankivell A. Andre N. Thomas-Keprta K. Allen C. McKay D.
Sulphur Spring: Busy Intersection and Possible Martian Analogue [#1892]
Life in extreme environments exhibiting conditions similar to early Earth and Mars, such as Sulphur
Spring, may harbor microbiota serving as both relics from the past as well as present day Martian

DeStefano A. L. Ford J. C. Winsor S. K. Allen C. C.
Microbial Life in the Deep Subsurface: Deep, Hot and Radioactive [#1702]
Recent studies, motivated in part by the search for extraterrestrial life, continue to expand the
recognized limits of Earth’s biosphere. This work explored evidence for life a high-temperature, radioactive
environment in the deep subsurface.

Weiss B. P. * Kirschvink J. L. Baudenbacher F. J. Vali H. Macdonald F. A. Wikswo J. P.
Reconciliation of Magnetic and Petrographic Constraints on ALH84001? Panspermia Lives On! [#2078]
New results from scanning SQUID magnetic microscopy place a strict constraint on the maximum temperature
(< 40 C) ALH84001 experienced since before formation of the carbonate blebs.

Treiman A. H. *
Heterogeneity of Remnant Magnetism in ALH84001: Petrologic Constraints [#1225]
Pyrrhotite in ALH84001 trapped a natural remnant magnetism, in random orientations, that has never seen
T > 40°C. The NRM was trapped late in the meteorite’s history, after its major brecciation, and probably
after deposition of the carbonate globules.

Thomas-Keprta K. L. * Wentworth S. J. McKay D. S. Gibson E. K.
Field Emission Gun Scanning Electron (FEGSEM) and Transmission Electron (TEM) Microscopy of
Phyllosilicates in Martian Meteorites ALH84001, Nakhla, and Shergotty [#1690]
Here we document the occurrence of phyllosilicates and alteration phases in three martian meteorites,
suggest formation conditions required for phyllosilicate formation and speculate on the extent of
fluid:rock interactions during the past history of Mars.

This page prepared by Michael Paine,
The Planetary Society Australian Volunteers