Cometary and meteorite swarm impact on planetary surfaces

Journal Article · Tue Aug 10 04:00:00 EDT 1982 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB087iB08p06668· OSTI ID:6084370

O'Keefe, J D; Ahrens, T J

The velocity flow fields, energy partitioning, and ejecta distributions resulting from impact of porous (fragmented) icy cometary nuclei with silicate planetary surfaces at speeds from 5 to 45 km/s are different than those resulting from the impact of solid ice or silicate meteorites. The impact of 1 g/cm/sup 3/ ice spheres onto an atmosphereless anorthosite planetary surface cratering flows that appear similar to those induced by normal density anorthosite meteorite impact. Both of these impactors lead to deep transient crater cavities for final crater diameters less than approx.1 to approx.10 km and for escape velocities < or approx. =10/sup 5/ cm/s. Moreover the fraction of internal energy partitioned into the planetary surface at the cratering site is 0.6 for both ice and anorthosite impactors at 15 km/s. As the assumed density of the hypothetical cometary nucleus or fragment cloud from a nucleus decreases to 0.01 g/cm/sup 3/, the fraction of the impact energy partitioned into planetary surface energy decreases to less than 0.01, and the flow field displays a toroidal behavior in which the apparent source of the flow appears to emanate from a disc or ringlike region rather than from a single point, as in the explosive cratering case. The edges of the crater region are in several cases depressed and flow downward, whereas the center of the crater region is uplifted. Moreover, the resultant postimpact particle velotity flow in some cases indicates the formation of concentric ridges, a central peak, and a distinct absence of a deep transient cavity. In contrast, transient cavities are a ubiquitous feature of nearly all previous hypervelocity impact calculations.

• Research Organization: Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125
• OSTI ID: 6084370
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 87:B8; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics &amp; Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CAVITIES
COMETS
CRATERS
EXCAVATION
HELMHOLTZ INSTABILITY
INSTABILITY
METEORITES
PLANETARY EVOLUTION
PLANETS
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
RAYLEIGH-TAYLOR INSTABILITY
SOLAR SYSTEM EVOLUTION
SURFACE PROPERTIES