The Observer's 20 photographs of the week

Paul Nicklen's photograph of emperor penguins was the overall winner of the Veolia Environnement wildlife photographer of the year 2012. It was taken at the edge of the frozen area of Antarctica's Ross Sea. Nicklen locked his legs under the lip of the ice so he could remain motionless Photograph: Paul Nicklen/Veolia Environnement Wildlife Photographer of the Year

A soldier with the Maya task force stands watch above the Zona 18 district of Guatemala City. Since the task force started their patrols, the murder rate has dropped from an average of five a day to two Photograph: Jorge Dan Lopez/Reuters

A Cambodian girl waits for the convoy transporting the coffin of late former king Norodom Sihanouk. Mourners lined the streets of Phnom Penh a to pay their last respects Photograph: Nicolas Asfouri/AFP

Smoke rises from a damaged building in the Syrian city of Aleppo, scene of intense fighting over the last three months Photograph: Manu Brabo/AP

A Premier Padmini taxi driver waits for customers in front of an apartment in a Mumbai suburb. The Padmini was manufactured in India by Premier Automobiles from 1964 to 2000. Following a government ban on taxis over 25 years old, the number of Padminis on the streets is dwindling Photograph: Vivek Prakash/Reuters

Displaced Pakistani students from the country's tribal areas sing with their teacher at a school on the outskirts of Islamabad Photograph: Nathalie Bardou/AP

At the Bayeux Calvados Awards for War Correspondents this week, Aris Messinis won the photography prize for his October 2011 coverage of the battle for Sirte. In this picture, Libyan rebels fire at forces loyal to Muammar Gaddafi as a comrade plays a guitar Photograph: Aris Messinis/AFP

Thousands of students gather to listen to Barack Obama at a campaign rally in Athens, Ohio Photograph: Jason Reed/Reuters

A demonstrator takes part in a protest against the Portuguese government's 2013 budget outside parliament in Lisbon Photograph: Patricia De Melo Moreira/AFP

A man photographs the space shuttle Endeavour as it makes its way through a residential area of Los Angeles on its way to the California Science Centre, where it is to go on permanent display Photograph: Reuters

Austrian Felix Baumgartner jumps out of his Red Bull Stratos capsule 23 miles above Earth as he begins his attempt to set the world record for the highest free fall Photograph: Getty

Kaleidoscope Cube by the artist Alex Ritchie is part of the Sculpture by the Sea exhibition along the Bondi to Bronte coastal walk in Australia Photograph: Mark Metcalfe/Getty

Photographer Peter van Agtmael was awarded the 2012 W Eugene Smith grant in humanistic photography for his work documenting the consequences of America's wars. Here, marines react to the explosion of an IED while on patrol in Afghanistan Photograph: Peter van Agtmael/Magnum

A police officer tries to restrain crowds during a religious procession in honour of The Lord of Miracles in Lima, Peru Photograph: Rodrigo Abd/AP

A health worker gives a boy a polio vaccine in a Christian neighborhood in Islamabad. Thirty-four million children need to be innoculated in Pakistan if the country is to eradicate the disease Photograph: Muhammed Muheisen/AP

Afghan boys play on a destroyed truck on a Kabul hilltop Photograph: Mohammad Ismail/Reuters

A police officer patrols with a sniffer dog in Rio de Janeiro's Jacarezinho slum, part of a state programme that establishes 'peacekeeping police units' in shantytowns previously controlled by drug traffickers Photograph: Felipe Dana/AP

A frightened Syrian boy cries in the street after an artillery shell destroyed his family home in the Shaar neighborhood of Aleppo Photograph: Zac Baillie/AFP

A female argonaut, or paper nautilus, a cephalopod species found off the California coast Photograph: Gary Florin/Cabrillo Marine Aquarium/AP

Demonstrators gather outside a branch of Starbucks before the start of an anti-austerity protest march through central London Photograph: Matt Dunham/AP