This image from the Mars Express spacecraft shows a pocket of water ice nestling in a martian crater, bathed in the late martian summer sun.

The shadow of the crater's rim, which towers 300 meters over the surrounding plains, prevents the ice from vaporising in the planet's thin atmosphere.  A dusting of frost survives inside the rim to the upper right, while the sun glimmers on its south-facing outer edge.

The 35 kilometer wide crater sits 70° north of the martian equator, in  low-lying region known as Vastitas Borealis.  Previous orbiters have spotted ice deposits in craters, but the High Resolution Color Camera aboard the probe is the first to return a three-dimensional colour image of an icy spot.  The ice may be up to 200 metres thick, and lies over a dune field that has formed in the sediment on the crater's floor.  The data were collected on 2 February, and this image was created for Nature last week,

Both the image and the captions were used without permission from Nature Magazine, volume 435, dated 9 June 2005.  You can see the original PDF file at this link.  Now, there are many important points here, many of which will escape the casual reader.  First, note the date of the data used to create the image- the European Space Agency collected it on February 2, 2005.  That would lead you to believe that this crater and its immense ice deposit were discovered then, only a few short months ago.  But in fact, it had already been photographed four years previously and in high detail mode by Malin Space Science Systems.  A little research yielded this link showing the crater was image in enough detail to show the nature of the glacier and crater clearly.

Some very important facts turn up- MSSS refers to the ice as "a persistent frost feature" rather than ice or a glacier.  The images clearly show a glacier field, and this was known two full years before the launch of the MER spacecraft.  The images were taken April 29th, 2001.  In other words, it was known that there is plenty of water on Mars two years before the rovers landed.  It was also known that the water in this one crater was roughly 8.2 cubic kilometers, or about 2 cubic miles of water.

This much water would fill a cube one and a quarter miles on an edge, and would be 5 times taller than the Empire State Building.  In this one crater alone, there is enough water to supply every person on Earth with about 1,400 liters- 700 two liter soda bottles of water for every man, woman, and child on Earth!

But there is more- the ESA identifies the material at the crater bottom as sediment!  In other words, it would seem that they feel this crater was filled by material that was deposited by the action of wind or water, but they made a point of identifying it specifically as sediment.  Now, one more very important point- what color is reflected off this ice?  Sky blue!  Where is that color coming from?  The sky, of course.  Look at the upper left edge of the ice and it appears to be reflecting the crater edge, as seen by the orange color- and clearly, you can identify a gap in the reflection that matches the gap in the crater wall.  We are seeing the color of Mars' sky reflecting in this glacier.

Many such ice filled craters have already been found on Mars, but remember that this one crater contains enough water ice to supply every person on Earth with about 370 gallons each.  That would be a tub about 4 feet by 8 feet and over a foot and a half deep!  There is no shortage of water and water ice on Mars; this one crater proves it and it has been known for years.

Summary Of Points

1.  There is enough water ice in the crater for everyone on Earth many times over

2.  This has been known about for over 4 years

3.  The color of the sky is reflecting in the glacier, showing that it is blue

4.  There are many more craters on Mars with this much ice in them