The forecast today is for temperatures dropping to about minus 80C (-112F) and snowfall that will vaporise before it reaches the ground. Mind you, this is the weather in the northern polar region of Mars, where Nasa’s Phoenix lander is beaming back data from its onboard weather station. Apart from gathering information on wind, temperature and pressure, an instrument called Lidar has beamed up a laser ray and detected snow falling from wispy clouds about 4km (2.5 miles) above the spacecraft’s landing site.

Phoenix also includes a robotic arm that digs up soil samples and a portable laboratory to test the soil. This equipment already has discovered a layer of frozen water under the ground surface. It also found evidence of calcium carbonate, the stuff of chalk, as well as particles that could be clay. Most carbonates and clays on Earth form only in the presence of liquid water, which could have existed on Mars billions of years ago. Today, however, liquid water cannot exist on the surface of Mars because its atmospheric pressure is too low.

Mars is a hostile place, though. Its atmosphere is mostly carbon dioxide, and 100 times thinner than that of Earth. It is also very dry – perhaps the nearest thing on Earth is the cold, dry valleys of Antarctica. But the presence of frozen water raises the intriguing possibility of one day colonising the planet using its icy resources.

Phoenix has been an astounding success, but it is now slowly dying. As the north pole of Mars begins its long, dark, frigid winter, the solar panels that power the spacecraft are running out of energy and by the end of October will largely shut down.