The formation of planetesimals in the early Solar System is hardly understood , and in particular the growth of dust aggregates above millimeter sizes has recently turned out to be a difficult task in our understanding [ Zsom et al .
2010 , A & A , 513 , A57 ] .
Laboratory experiments have shown that dust aggregates of these sizes stick to one another only at unreasonably low velocities .
However , in the protoplanetary disk , millimeter-sized particles are known to have been ubiquitous .
One can find relics of them in the form of solid chondrules as the main constituent of chondrites .
Most of these chondrules were found to feature a fine-grained rim , which is hypothesized to have formed from accreting dust grains in the solar nebula .
To study the influence of these dust-coated chondrules on the formation of chondrites and possibly planetesimals , we conducted collision experiments between millimeter-sized , dust-coated chondrule analogs at velocities of a few \mathrm { cm s ^ { -1 } } .
For 2 and 3 mm diameter chondrule analogs covered by dusty rims of a volume filling factor of 0.18 and 0.35-0.58 , we found sticking velocities of a few \mathrm { cm s ^ { -1 } } .
This velocity is higher than the sticking velocity of dust aggregates of the same size .
We therefore conclude that chondrules may be an important step towards a deeper understanding of the collisional growth of larger bodies .
Moreover , we analyzed the collision behavior in an ensemble of dust aggregates and non-coated chondrule analogs .
While neither the dust aggregates nor the solid chondrule analogs show sticking in collisions among their species , we found an enhanced sicking efficiency in collisions between the two constituents , which leads us to the conjecture that chondrules might act as “ catalyzers ” for the growth of larger bodies in the young Solar System .