NASA/JPL/Malin Space Science Systems

This picture of a crater resembling a “happy face” was acquired earlier this week on 28 January 2008. The unnamed crater is about 3 kilometers (1.9 miles) across. It is located among the Nereidum Montes, north of the Argyre basin, near 45.1°S, 55.0°W. North is toward the right and sunlight illuminates the scene from the upper right.

Oh, it's already the second smile discovered one Mars. Here's the first:

Photo also by MSSS