International Space Station. - Hello, is this planet Earth?: my view from the International Space Station

One of the remarkable things about seeing the Earth from space is that by day, with the naked eye, its very hard to spot any signs of human habitation.

Instead, our planet reveals itself as a vast geological puzzle, its features spanning entire continents, sculpted by natures forces and the passage of time. Wind and rare precipitation have shaped the Sahara into a canvas of exquisite art, with sand dunes towering over 150 meters high clearly visible from space. Volcanoes trace the outline of Earths tectonic plates, often smoking gently and giving away the presence of an active core not far beneath. Glaciers carve out entire mountain ranges as they grind inexorably towards the oceans. By night its a different story. You can easily trace the pattern of human migration and settlement by the lights of towns, cities, motorways and man-made structures. Even our thirst for the planets resources stands outthe lights of a thousand fishing boats in the Gulf of Thailand or the dazzling oil fields in the Middle East.

Its impossible to look down on Earth from space and not be mesmerized by the fragile beauty of our planet. I was struck by just how thin our atmosphere really isthat tiny strip of gas that sustains all life and differentiates our planet from the barren, hostile conditions of Mars or Venus. I became determined to share this unique perspective of the one place we can all call home. It may come as a surprise to learn that I was not a keen photographer when I launched into space. Its not that I didnt enjoy photography; its just that I never seemed to have a good eye for a picture. In that respect I have a lot to thank planet Earth for: shes a beautiful subject and made my job extremely easy! Even my early attempts rewarded me with some stunning vistasthe Cascade mountains, frozen sea in the Hudson Bay and spectacular sunrises to name a few.

From the International Space Station (ISS) you can see over 1000 kilometers in any direction. Passing over the French Alps I could enjoy a view stretching from Greece to the UK with just the turn of my head. At first, the magnitude of this scene was a bit overwhelming, and my photographic skills did not extend much beyond point and shoot. However, as I settled into this new environment my perspective began to change. With sixteen orbits every day, it was not long before I felt I knew planet Earth pretty well! For example, it may sound strange, but I was talking about Madagascar recentlysomewhere I have yet to visitwith the familiarity of someone who has traveled there extensively. I began to focus on the details: noting the mountain lakes in the Himalayas that would lead me to Mount Everest, perhaps, or checking up on some small volcano in Kamchatka to see if it was still erupting. When traveling at nearly 30,000 kilometers per hour, this level of detail requires some careful planning.

Each morning, I would check to see where the ISS would be passing over, decide which pictures I would try to capture that day and then set several alarms to remind me. Often, my alarm would go off and Id have my hands full of a science experiment or be in the middle of a maintenance activitya case of better luck next time. However, there was a huge sense of satisfaction when all the planning paid off and I was rewarded with a perfectly lit overhead pass of the Pyramids, say, or a rare glimpse of Antarctica. As much as I enjoyed the hunt for those more elusive targets, many of my most treasured pictures were not the result of meticulous planning. Often I would just happen to be passing by the Cupola window and be struck by the most incredible viewa sea of thick green fog as we traveled through the aurora borealis or the disco lights of a hundred lightning flashes along a massive storm front.

Night photography in low-light conditions presented a new set of difficulties. Reflections from the numerous light sources inside the ISS were a constant problem. We used a blackout curtain around the window with a hole for the lens to poke through to prevent this from ruining a picture. The next challenge was how to get a shot in sharp focus with long exposure times and so much relative motion between the camera and the object. The best method relied mainly upon a steady hand and a good eye for tracking targetssomething for which my previous job as a helicopter pilot had prepared me quite well. As someone who had only ever used auto mode on a camera before, I never imagined that I would be intuitively adjusting aperture, shutter speeds and ISO settings depending on the rapidly changing lighting conditions, nor discussing the merits of a particular lens over dinner in space with my fellow astronauts. Camaraderie on a space station is clearly important and photography is one of the many common interests that astronauts from all nations can share. In the first few weeks on board the ISS, my pictures certainly owed a great deal to the patient advice of crewmates Scott Kelly and Tim Kopra.