  This paper puts forward a possible new indicator for the presence of
moderately advanced civilizations on transiting exoplanets. The idea is to
examine the region of space around a planet where potential geostationary or
geosynchronous satellites would orbit (herafter, the Clarke exobelt).
Civilizations with a high density of devices and/or space junk in that region,
but otherwise similar to ours in terms of space technology (our working
definition of "moderately advanced"), may leave a noticeable imprint on the
light curve of the parent star. The main contribution to such signature comes
from the exobelt edge, where its opacity is maximum due to geometrical
projection. Numerical simulations have been conducted for a variety of possible
scenarios. In some cases, a Clarke exobelt with a fractional face-on opacity of
~1E-4 would be easily observable with existing instrumentation. Simulations of
Clarke exobelts and natural rings are used to quantify how they can be
distinguished by their light curve.
