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D.D. Durda, S.A. Stern, J.Wm. Parker, W.B. Colwell, H.F. Levison, D.M. Hassler, D.C. Slater (SwRI)
The viability and reality of the so-called Vulcanoid population of small bodies orbiting interior to Mercury has long been debated (e.g., Campins, 1996, ASP 107, 85). Dynamical studies reveal that objects with diameters >1 km can survive in the 0.07 to 0.20 AU region for long time scales, perhaps the age of the solar system. Further, although ground-based observational searches have been conducted, they are not particularly contraining, allowing significant numbers of objects with diameters d as large as 30 to 50 km to exist.
We have recently investigated the viability of the Vulcanoid population ensemble using previously developed collision codes (Stern, 1995, AJ, 110, 856), with the objective of determining how large a population might in fact be able to survive. We find that, for the assumption of a collisional equilibrium population power law (i.e., Dohnanyi) structure, the critical population whereby the largest primordial objects in the population have survived for 4.5 Gyr appears to be one with less than several hundred objects with d > 2 km.
We also report initial results of observational searches for Vulcanoids in images obtained using the SOHO LASCO C3 coronograph and the SWUIS instrument aboard Space Shuttle mission STS-93.