We present some preliminary results of a series of catastrophic break-up experiments carried out in the open, against targets of natural and artificial rock, with and without a harder core. These experiments were aimed at investigating the outcomes of hypervelocity impact disruption phenomena, designed to understand the influence of large-scale collisions on the evolution of asteroids and other small solar system bodies. For the first time in this kind of experiments, evidence was found of collimated jets, i.e. the ejection of a statistically significant number of fragments all closely aligned about some preferential planes. Moreover, the presence of some groups of fragments lying close to each other on the ground was also detected.

The Infrared Astronomical Satellite has provided extensive observations of the zodiacal cloud at high spatial resolution which will not be matched in the forseeable future. Within the zodiacal cloud, IRAS discovered extended dust structures providing the link between the interplanetary dust complex and the asteroids and comets which are its source. These are the asteroid dust bands and the cometary dust trails.

Samples of interplanetary dust particles (IDPs) have now been collected from the stratosphere, from the Earth’s ocean beds, and from the ice caps of Greenland and Antarctica The most likely candidates for the sources of these particles are comets and asteroids. Comparison of the infrared spectra, elemental compositions, and mineralogy of the collected dust with atmospheric entry models and data obtained from cometary probes and telescopic observations has provided important constraints on the possible sources of the various types of collected dust. These constraints lead to the following conclusions. First, most of the deep sea, Greenland, and Antarctic spherules larger than 100 μm are derived from asteroids. Second, the stratospheric IDPs dominated by hydrated layer-lattice silicate minerals are also most likely derived from asteroids. Finally, the stratospheric IDPs dominated by the anhydrous minerals olivine and pyroxene are most likely from comets. The consequences of these parent body assignments are discussed.

This paper reviews our current knowledge of interstellar and circumstellar dust from an observational point of view. It is concluded that interstellar dust is highly heterogenous. It consist of a large number of different materials formed in a great variety of stellar birthsites under varying conditions and each with a highly isotopically anomalous composition in its main elements.

This review examines to what degrees the present chemical equilibrium condensation models are effective in predicting chemical composition of grains observed in a variety of cosmic environments. The composition expected from the equilibrium calculations is reviewed separately for refractory (rocky and metallic) and volatile (icy) components. Comments are given on the limitation of the equilibrium calculations in predicting the grain composition. By taking cometary ice as a typical cosmic volatile condensate, it is pointed out that its composition is far from that expected from the equilibrium models. Theories on the formation of cometary volatiles are reviewed, and an observational clue helpful to testing the theories is pointed out. Discussion is given on the advantage for formation of organic materials from volatile solids.

Large far-infrared excesses in some nearby main-sequence stars, revealed by the Infrared Astronomical Satellite (IRAS), have been interpreted as being due to thermal radiation from dust orbiting the stars, heated to about 100K by the stellar radiation (Aumann et al. 1984; Aumann 1985; Sadakane and Nishida 1986). The existence of solid circumstellar material is commonly interpreted in the context of planet formation, and the dust has been suggested to be formed by collisions of planetesimals (Nakano 1987, 1988).

Off-disk implantation of ancient solar wind into a protoplanetary dust cloud can explain the present amounts of solar-type noble gases in gas-rich meteorites and Venus, even if the dust cloud is very opaque along its midplane.

We synthesized a SiO condensate trapping H20 and H20 ice deposited on it. An IR spectrum of the condensate and that of a protostar NGC 7538/IRS 9 were compared. The spectrum of the condensate agreed well with the protostellar spectrum.

The chemical composition of galactic cosmic rays in their sources is similar to that of interstellar clouds or grains which are relatively enriched in refractory and siderophile elements as compared with the chemical composition of the solar atmosphere. Taking into account this fact, it is shown that the cosmic ray source matter can be identified as the dust or grains observed in the envelopes of red supergiant stars or the matter originally ejected from supernova explosions.

At Laboratory Astrophysics we are simulating the most relevant conditions in interstellar space in order to follow the chemical and physical evolution of, among others, interstellar organic grain mantles.

Usually in presenting a summary report of a meeting one tries to pick out the highlights. In the present instance I am tempted to say that the meeting was its own highlight because there were so many fine presentations covering such a wide range of interrelated topics. The organizers are clearly to be congratulated on their timing.