  We have quantified the potential capabilities of detecting local brightness
asymmetries in circumstellar disks with the Very Large Telescope Interferometer
(VLTI) in the mid-infrared wavelength range. The study is motivated by the need
to evaluate theoretical models of planet formation by direct observations of
protoplanets at early evolutionary stages, when they are still embedded in
their host disk. Up to now, only a few embedded candidate protoplanets have
been detected with semi-major axes of 20-50 au. Due to the small angular
separation from their central star, only long-baseline interferometry provides
the angular resolving power to detect disk asymmetries associated to
protoplanets at solar system scales in nearby star-forming regions. In
particular, infrared observations are crucial to observe scattered stellar
radiation and thermal re-emission in the vicinity of embedded companions
directly. For this purpose we performed radiative transfer simulations to
calculate the thermal re-emission and scattered stellar flux from a
protoplanetary disk hosting an embedded companion. Based on that, visibilities
and closure phases are calculated to simulate observations with the future beam
combiner MATISSE, operating at the L, M and N bands at the VLTI. We find that
the flux ratio of the embedded source to the central star can be as low as 0.5
to 0.6 % for a detection at a feasible significance level due to the heated
dust in the vicinity of the embedded source. Furthermore, we find that the
likelihood for detection is highest for sources at intermediate distances
$r\approx2$-$5$ au and disk masses not higher than $\approx10^{-4}$
M$_{\odot}$.
