  The arrival of solid particles from outside our solar system would present us
with an invaluable source of scientific information. Attempts to detect such
interstellar particles among the meteors observed in Earth's atmosphere have
almost exclusively assumed that those particles moving above the Solar System's
escape speed -- particles on orbits hyperbolic with respect to the Sun-- were
precisely the extrasolar particles being searched for. Here we show that
hyperbolic particles can be generated entirely within the Solar System by
gravitational scattering of interplanetary dust and meteoroids by the planets.
These particles have necessarily short lifetimes as they quickly escape our
star system; nonetheless some may arrive at Earth at speeds comparable to those
expected of interstellar meteoroids. Some of these are associated with the
encounter of planets with the debris streams of individual comets; however,
such encounters are relatively rare. The rates of occurrence of
hyperbolically-scattered sporadic meteors are also quite low. Only one of every
10,000 optical meteors observed at Earth is expected to be such a locally
generated hyperbolic and its heliocentric velocity is typically only a hundred
meters per second above the heliocentric escape velocity at Earth's orbit.
Mercury and Venus are predicted to generate weak 'hyperbolic meteor showers':
the restrictive geometry of scattering to our planet means that a radiant near
the Sun from which hyperbolic meteors arrive at Earth should recur with the
planet's synodic period. However, though planetary scattering can produce
meteoroids with speeds comparable to interstellar meteors and at fluxes near
current upper limits for such events, the majority of this locally-generated
component of hyperbolic meteoroids is just above the heliocentric escape
velocity and should be easily distinguishable from true interstellar
meteoroids.
