On: NASA: Mars rover Curiosity finds bright object

[sampo]

Happened to a Soviet lander on Venus in 1982:

"The quartz camera windows were covered by lens caps which popped off after descent. Venera 14, however, ended up measuring the compressibility of the lens cap, which landed right where the probe was to measure the soil."

http://en.wikipedia.org/wiki/Venera_14#Landing