Images by Associated Press photographer Natacha Pisarenko gave us an enchanting glimpse of an Antarctic summer. She and reporter Luis Andres Henao followed scientists from different fields searching for alien-like creatures, hints of pollution trapped in pristine ancient ice, leftovers from the Big Bang, biological quirks that potentially could lead to better medical treatments, and perhaps most of all, signs of unstoppable melting.

Tens of thousands of Argentines marched through the capital in a driving rain Wednesday demanding answers in the mysterious death of prosecutor Alberto Nisman exactly one month after he was found in his bathroom with a bullet in his right temple.

Rio de Janeiro's world-famous samba school parades held their grand finale as the five-day-long Carnival celebration came to an end on Tuesday morning.

On Wednesday, some Christians in the region ushered in the first day of Lent, a 40-day period of penitence and reflection, by receiving a sign of the cross, marked with black ashes on their foreheads as the priest reminded each Christian of Genesis 3:19: "For dust you are and to dust you shall return."