NASA's Phoenix spacecraft has not only discovered evidence of past water at its landing site on Mars, but it has also now spotted falling snow for the first time.

Soil experiments at the landing site reveal the presence of two minerals - calcium carbonate and sheet silicate - that are known to be formed in liquid water. However they aren't yet sure how this happened.

A laser onboard the Phoenix also detected snow falling from clouds more than two miles above its location in the northern arctic plains. The snow disappeared before it reached the ground.

Phoenix landed in the arctic plains on Mars in May, where it is on a three month mission to study whether the Martian environment could be friendly to microbial life. Thus far, its biggest discovery has been confirming the presence of ice on the planet. The lander also discovered that the soil is slightly alkaline, and contained important nutrients and minerals.

Today Mars is cold and dry, with no signs of water on the surface, however researchers believe that the planet was once warmer and wetter.

Mars today is frigid and dry with no sign of water on the surface, but researchers believe the planet once was warmer and wetter.

Phoenix's three month mission was extended through the end of the year, if it can survive that long. Summer is nearing an end, and less sunlight is able to reach the spacecraft's solar panels. In November it will be briefly out of touch with ground controllers when the sun is between Earth and Mars.

In the meantime, scientists are in a race against time, trying to use the remaining four of the craft's eight tiny test ovens before the lander dies. These ovens are made to sniff for traces of organic (carbon-based) compounds, which are considered the building blocks of life. So far experiments have failed to turn up any definitive evidence of organics.