Scientists say it is highly unlikely that there is any freestanding or flowing water on Mars, and almost certainly no life. So we'd like to get a good explanation for this photo taken by the Mars Express orbiter. In stark contrast to the surrounding familiar rust-red rock of the planet is this ribbon of blue-green "something" in a canyon. If we were to see such a feature in an aerial photo of the Earth, we would quickly assume that it is a body of water.
A number of questions arise: Are the colors accurate? The US orbiters have not shown such colors in any of their photos. If the colors are accurate, what accounts for them? Lifeless mineral deposits? Or do they reveal the existence of water... or, more remarkably, a kind of Martian blue-green algae or lichen?