The most substantial scientific evidence of water flowing on the surface of Mars was obtained from pictures of Martian gullies – NASA’s Mars global surveyor. NASA has been deriving images from the planet since 1999. After almost ten years of discovering Mars from orbit, photographs by NASA’s surveyor revealed what seemed to be light-colored deposits on two crater walls. There was a notable difference between pictures taken in 2004 and 2005, compared to those captured in 1999. On Dec 6, 2006, NASA released the photos of two craters – Terra Sirenum and Centauri Montes, showing the presence of liquid water on Mars.

According to a scientist, the deposits looked like the substance was left behind after water filtered through the gullies. Since the material took the shape of filtered residue, it is believed that water was the fluidizing material. Evaporation might have taken place quickly due to the low temperature and pressure on the planet’s surface. While Mars has always been known to have water in ice and vapor state, the idea of the presence of liquid water was far-fetched.

The presence of liquid water on the planet is something that some scientists still believe, which, if the case, makes it possible for the existence of microbes on Mars. Although other scientists suggest that the flow patterns could have been the aftermath of rock falls or landslides, the nature of these craters contradicts their argument. The changes have been more likely to have originated from a fluid substance which is thought to be water in this case.