And the answer is...
Mercury can be seen just before sunrise or just after sunset on some clear nights.
The StarChild site is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), within the Astrophysics Science Division (ASD) at NASA/ GSFC.
StarChild Authors: The StarChild Team
StarChild Graphics & Music: Acknowledgments
StarChild Project Leader: Dr. Laura A.
Whitlock
Curator:
Responsible NASA Official: