DG Tau is a low-mass young star whose strongly accreting disk shows a
variable 10 micron silicate feature, that may even turn temporarily
from emission to absorption.
Aiming to find its physical reason, we analysed multiepoch VLTI/MIDI
interferometric observations. We found that the inner disk (r<3 au)
exhibits a 10 micron absorption feature related to amorphous silicate
grains, while the outer disk shows a variable crystalline feature in
emission, similar in shape to the spectrum of comet Hale-Bopp. We
propose that the mid-infrared variability is originated in the outer
disk, where the mass of the dusty material above the disk plane may
change with time, possibly due to turbulence in the disk.
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