Image: Rainbow aurora captured from space station

Auroras occur when particle radiation from the Sun hits Earth's upper atmosphere, making it glow in a greenish blue light. ESA astronaut Alexander Gerst has one of our planet's best views of this phenomenon, circling 400 km up on the Station.

Here, the last remnants of sunlight can be seen as a blue streak on the left side. Above it is the yellow hue of our atmosphere reflecting the sunlight. This thin band is all that protects us from solar radiation.

In the foreground, the Space Station's Canadarm2 robotic arm is stowed, waiting to receive the next supply spacecraft to visit the microgravity laboratory.

Alexander worked as a geophysicist and volcanologist before he was chosen as an ESA astronaut in 2009. His Blue Dot mission includes an extensive programme of experiments in physical science, biology and human physiology as well as radiation research and technology demonstrations. All of the research makes use of the out-of-this-world laboratory to improve life on Earth or prepare for further human exploration of our Solar System.