Abstract
I discuss some recent estimates of protoplanetary disk masses from dust emission, and suggest that masses have been systematically underestimated. I also consider the implications of recent results on the outbursting FU Ori objects, which demonstrate the need for substantial amounts of mass in disks within 1 AU, at least at early evolutionary stages. These considerations lend more weight to suggestions that protoplanetary disks have relatively massive 'dead zones', which may aid in the formation of the so-called 'transitional disk' systems, objects in which the inner disk has been strongly cleared of small dust even though the outer disk is very substantial.
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