Let it snow, let it snow...

Belated birthday greetings to Nasa. The US space agency turned 50 on Wednesday, having been formally established on October 1, 1958.

After five decades of boldly going where no one has gone before, through triumph and tragedy, Nasa is facing a mid-life crisis and an uncertain future.

Does it focus on making space travel economical, setting up a permanent colony on the moon, travelling to Mars, or exploring the depths of the universe, unlocking the mysteries of distant worlds?

But there's also reason to cheer. The Phoenix Mars Lander has discovered snow on the red planet falling from Martian clouds. We already know there's ice.

Now Nasa just needs to look for little green Martians making snowmen or playing ice hockey...