Images acquired by the Mars Global Surveyor may have found evidence that water flowed on the surface of the red planet as recently as a few years ago. The Orbiter has imaged gullies and trenches that scientists believe are proof of recent water activity flowing down cliffs and steep crater walls.
The Mars rovers have been instrumental in determining that water once flowed on Mars in ancient times however the images acquired by the Global Surveyor are the first indication that liquid water still exists on the planet now. The probe found two gullies which were originally imaged in 1999 and 2001 and then re-imaged in 2004 and 2005 that showed changes which were consistent with water flowing down the crater walls. This also raises questions as to how the water has remained in the liquid form beneath the surface and how widespread it may be. It also raises the tantalising question as to whether there exists a below-ground environment that is conducive to life.
The orbiter imaged approximately 98 percent of the Mars in 1999 and approximately 30 percent of the planet was reimaged in 2006. Using the data acquired from these images the orbiter’s imaging team have also been assessing the rate at which new impact craters appear on the martian surface. The new images have revealed 20 fresh impact craters ranging in diameter from 7 feet (2 meters) to 486 feet (148 meters) that were not present seven years earlier. 

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