Early solar system events and timescales

Some recent information on the Mn-Cr and Al-Mg systems is reviewed. This in formation is used to derive constraints on the timing of processes and even ts, which took place in the early solar system. Using reasonable assumption s, a timeline is constructed where the estimated age of the solar system is similar to 4571 Ma. This age is taken to mark the time when most calcium-a luminum-rich inclusions (CAIs) were starting to form, a process that may ha ve lasted for several 10(5) years. Almost contemporaneously small planetesi mals have accreted that served to store these CAN for later dispersal among larger planetesimals. By the time large numbers of planetesimals of severa l tens of kilometers in size had formed, the interior of these objects star ted to melt through the decay of Al-26 Collisional disruption of these plan etesimals allowed gases, dust, and melt to escape into the surrounding spac e. The fine droplets of melt reacted with gas and dust to form chondrules, which, after rapid cooling, were partially re-accreted onto the residual ru bble pile. This process of primary chondrule formation, in most cases invol ving several generations of planetesimals, most plausibly lasted only for s imilar to2 Ma. Towards the end of this period and during the following 3 to 4 Ma planetary objects of several hundred kilometers in size were formed. They still stored enough energy to continue melting from the inside to fina lly differentiate into chemically stratified layers, with basaltic volcanis m occurring within a few million years.