And the answer is...

Shuttle

The reddish appearance of Mars is believed to be caused by an iron-rich soil.

Viking image of the surface of Mars
The surface of Mars from Viking

Shuttle

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: J.D. Myers
Responsible NASA Official: Amber Straughn