Deep HST broad-band images taken with ACS and WFPC2 of the giant ( \sim 1000 AU diameter ) dark silhouette proplyd 114-426 in the Orion Nebula show that this system is tilted , asymmetric , warped and photoevaporated .
The exquisite angular resolution of ACS allows us to map the distribution of dust grains at the northern translucent edge of the disk , dominated by the photoevaporative flow .
Using the Mie theory for standard circumstellar disk grains , we find evidence for a spatial gradient in grain size .
The typical dust radius , \simeq 0.2 - 0.7 ~ { } \mu m ( less than what reported by previous studies ) becomes smaller as the distance from the disk center increases , consistent with the expectations for the dynamic of dust entrained in a gaseous photoevaporative wind .
Our analysis of the disk morphology and location within the nebula indicates that this system is photoevaporated by the diffuse radiation field of the Orion Nebula , while being shielded from the radiation coming directly from the central Trapezium stars .
We estimate the mass-loss rate from the disk surface and the time-scale for total disk dissipation , which turns out to be of the order of 10 ^ { 4 } yr .
Such a short time , of the order of 1/100 of the cluster age , indicates that this system is seen on the verge of destruction .
This is compatible with the exceptional nature of the disk , namely its combination of huge size and low mass .
Finally , we briefly discuss the viability of possible mechanisms that may lead to the peculiar morphology of this system : external UV flux , binary star and past close encounter .