Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

June 8, 1998 A Mars Glint Credit: Mars Global Surveyor Project, MSSS, JPL, NASA

Explanation: If aligned just right, even a planet can produce a glint. The above combined pictures of Mars make the red planet appear unusually elongated - Mars is really almost spherical. However, these pictures were taken when the Sun was nearly directly behind the Mars Global Surveyor (MGS) spacecraft. This created a view for MGS where every part of Mars that was visible was also illuminated by the Sun. From this vantage point, though, sunlight reflects off the Martian surface and atmosphere producing a bright spot in the centre - a glint. The brightness, colour, and extent of the glint carry valuable information about the composition and physical properties of Mars.