Title: Analog Experiments on Tensile Strength of Dusty and Cometary Matter,
Abstract: The tensile strength of small dusty bodies in the solar system is determined
by the interaction between the composing grains. In the transition regime
between small and sticky dust ($\rm \mu m$) and non cohesive large grains (mm),
particles still stick to each other but are easily separated. In laboratory
experiments we find that thermal creep gas flow at low ambient pressure
generates an overpressure sufficient to overcome the tensile strength. For the
first time it allows a direct measurement of the tensile strength of
individual, very small (sub)-mm aggregates which consist of only tens of grains
in the (sub)-mm size range. We traced the disintegration of aggregates by
optical imaging in ground based as well as microgravity experiments and present
first results for basalt, palagonite and vitreous carbon samples with up to a
few hundred Pa. These measurements show that low tensile strength can be the
result of building loose aggregates with compact (sub)-mm units. This is in
favour of a combined cometary formation scenario by aggregation to compact
aggreates and gravitational instability of these units.