Stellar spots may in some cases produce radial velocity (RV) signatures
similar to those of exoplanets. To further investigate the impact of spots, we
aim at studying the detectability of Earth mass planets in the habitable zone
(HZ) of solar type stars, if covered by spots similar to the sunspots. We have
used the Sunspots properties recorded over one solar cycle between 1993 and
2003 to build the RV curve that a solar type star seen edge-on would show, if
covered by such spots with Tsun -Tspot = 550K. We also simulate the RV of such
a spotted star surrounded by an Earth mass planet located in the HZ. Under
present assumptions, the detection of a 1 M Earth planet located between 0.8
and 1.2 AU requires an intensive monitoring (weekly or better), during several
years of low activity phasis. The temporal sampling is more crucial than the
precision of the data (assuming precisions in the range [1-10] cm/s). Cooler
spots may become a problem for such detections. Also, we anticipate that
plages, not considered in this paper, could further complicate or even
compromise the detections
