The NASA History Program Office is pleased to announce the availability of When Biospheres Collide:  A History of NASA’s Planetary Protection Programs (NASA SP-2011-4234) by Michael Meltzer.  Attached is a double-sided flyer with information about this book, including ordering information.  It is also available at http://history.nasa.gov/SP-4234.pdf online and soon will be available in e-book formats.