We present very accurate abundances for 19 elements in a sample of 63 solar twins and analogs. Abundance ratios [X/Fe] as a function of [Fe/H] are in good agreement with the well established patterns of Galactic thin-disk chemical evolution. Interestingly, the majority of our stars show a significant correlation between [X/Fe] and condensation temperature Tc. We speculate that this is a signature of the planet formation that occurred around the Sun but not in the majority of solar twins. If true, although rare (frequency of 15%), planetary systems like ours may be detectable through a very detailed inspection of the chemical compositions of their host stars.