Before-and-after views where a gully flowed in a crater in the Centauri Montes region. The left image shows the crater in 1999 when no light-toned deposit was present. The right image was taken in 2005.
Images of this gully and one more, both taken by Mars Global Surveyor, suggest liquid water carried sediment in the past seven years. Liquid water is considered necessary for life, so the findings heighten intrigue about possible microbial life on Mars.
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