Prolonged global catastrophes from oblique impacts

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Abstract
Most impacts occur obliquely rather than vertically as typically modeled. Laboratory experiments permit documenting the effects of impact angle on energy partitioning and related phenomena. Three results have particular significance for understanding the possible global atmospheric and biospheric response to a major impact. First, at low impact angles (2θ for impact angles between 45° and 15°. This contrasts with peak stress levels, which decrease as sin2θ, and reflects the effect of shear heating along the projectile/target interface. As a consequence, vaporization of easily volatized materials (water, carbonates) can occur without initially large energy densities, thereby potentially adding to—rather than escaping from—the atmosphere. Thus, nitrate production from such a swarm could greatly exceed that from a single vertical impactor not only due to the greater ionization efficiency by numerous small objects and their much longer cumulative atmospheric path lengths but also due to increased coupling with the atmosphere. Third, the ricochet component appears to be embedded in an expanding vapor cloud sufficient to drive gases away from the downrange trajectory. For a major collision, this process would substantially increase the zone and duration of biomass incineration in a downrange “fireline,” as well as providing a mechanism for inserting substantial material into orbit. A potential consequence of orbital insertion is the possible development of a temporary debris ring. Such a ring might substantially prolong the climatic response to an impact through the reduced solar constant and through strong thermal gradients created by the ring shadow. Moreover, impact debris, including the cosmic signature, may be titrated into the geologic record well after the initial collision (<10 m.y.).

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