Space shuttle Atlantis and its crew of seven astronauts ended an 11-day journey of nearly 4.5 million miles with a 9:44 a.m. EST landing Friday at NASA's Kennedy Space Center in Florida.

A large bloom of cyanobacteria, more commonly known as blue-green algae, spread across Guatemala's Lake Atitlán in green filaments and strands that are clearly visible in this simulated-natural-color image from November 22, 2009.

Acquired January 16, 2005, this true-color image shows part of the inhospitable limestone landscape of western Madagascar, with bare rocks and vegetation forming a patchwork of gray and green.