Linked Life Data

11538404

Source:http://linkedlifedata.com/resource/pubmed/id/11538404

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
E6
pubmed:dateCreated
1996-3-25
pubmed:abstractText
A simple analytic model for the catastrophic disruption and deceleration of impactors in a thick atmosphere is used to (1) reproduce observed Venusian cratering statistics and (2) generate radar-dark disks by the impact of atmospheric shock waves with the surface. When used as input to Monte Carlo simulations of Venusian cratering, the model nicely reproduces the observed low diameter cutoff. Venusian craters are found to be more consistent with an asteroidal rather than a cometary source. The radar-dark "shadows" of the title are surface features, usually circular, that have been attributed to airbursting impactors. A typical craterless airburst is the equivalent of a approximately 10(6) megaton explosion. The airburst is treated as a massive, extended explosion using a thin-shell, isobaric cavity approximation. The strong atmospheric shock waves excited by the airbust are then coupled to surface rock using the usual impedance matching conditions. Peak shock pressures experienced by surface rock typically exceed 0.2 GPa for distances 15-30 km from ground zero (the place on the surface immediately beneath the site of the airburst), and 1 GPa for 10-20 km. These high shock pressures are felt to considerable depth, often more than a kilometer. Beneath the airburst the shock could reduce surface rocks to fine rubble, while at greater distance the weaker shock would leave fields of broken blocks, perhaps in part accounting for radar-bright halos that often surround the dark shadows.
pubmed:keyword
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
S
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0148-0227
pubmed:author
pubmed:issnType
Print
pubmed:day
25
pubmed:volume
97
pubmed:owner
NASA
pubmed:authorsComplete
Y
pubmed:pagination
10243-55
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Airburst origin of dark shadows on Venus.
pubmed:affiliation
NASA Ames Research Center, Moffett Field, California, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S.