Recent observations of microlensing events in the Large Magellanic Cloud by the MACHO and EROS Collaborations suggest that an important fraction of the galactic halo is in the form of massive halo objects (MHO) with mass $\sim 0.1M_{\odot }$. We outline a scenario in which dark clusters of MHO with mass $\sim 0.1M_{\odot }$ and ${\mathrm{H}}_2$ molecular clouds form in the halo at galactocentric distances larger than ∼10-20 kpc, provided baryons are a major constituent of the halo. Possible signatures of our picture are discussed.

• Received 11 July 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.14