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Determining the mechanisms that drive the evolution of protoplanetary disksis a necessary step to understand how planets form. Here we measured the massaccretion rate for young stellar objects at age >5 Myr, a critical test for thecurrent models of disk evolution. We present the analysis of the spectra of 36targets in the ~5-10 Myr old Upper Scorpius region for which disk masses weremeasured with ALMA. We find that the mass accretion rates in this sample of oldbut still survived disks are similarly high as those of the younger (<3 Myrold) star-forming regions of Lupus and Cha I, when considering the dependenceon stellar and disk mass. In particular, several disks show high mass accretionrates >10^-9 Msun/yr while having low disk masses. Furthermore, the medianvalues of the measured mass accretion rates in the disk mass ranges where oursample is complete at a level ~60-80% are compatible in these three regions. Atthe same time, the spread of mass accretion rates at any given disk mass isstill >0.9 dex even at age>5 Myr. These results are in contrast with simplemodels of viscous evolution, which would predict that the values of the massaccretion rate diminish with time, and a tighter correlation with disk mass atage>5 Myr. Similarly, simple models of internal photoevaporation cannotreproduce the observed mass accretion rates, while external photoevaporationmight explain the low disk masses and high accretion rates. A partial possiblesolution to the discrepancy with the viscous models is that the gas-to-dustratio of the disks at >5 Myr is significantly different and higher than thecanonical 100, as suggested by some dust and gas disk evolution models. Theresults shown here require the presence of several inter-playing processes,such as detailed dust evolution, external photoevaporation and possibly MHDwinds, to explain the secular evolution of protoplanetary disks.

X-Shooter survey of disk accretion in Upper Scorpius I. Very high accretion rates at age>5 Myr