Newswise — It's been 50 years this month since the first woman, Soviet cosmonaut Valentina Tereshkova, traveled into space (June 16, 1963) - yet it took the United States another 20 years to send its first female astronaut, Sally Ride, into space on June 18, 1983. Why was there such a gap between the two nations in achieving this small measure of gender equality in space?

The story becomes even more difficult to comprehend when you consider that in 1961 NASA recruited a group of 13 women for America's space program. These women - who came to be known as the Mercury 13 - were all accomplished pilots who passed the same rigorous physical tests given to male applicants (and, in some cases, surpassed the men), but they were ultimately prevented from taking part in the Mercury 13 mission because of their gender. Mount Holyoke College's Martha Ackmann, a senior lecturer in gender studies and the author of The Mercury 13: The True Story of Thirteen Women and the Dream of Space Flight (2003, Random House), has made a cause celebre of the unfair treatment of these women - and she is available to discuss these two momentous anniversaries in space travel history and this sad chapter of discrimination in U.S. history.

Ackmann, a 2008 Guggenheim Fellow, has long been a passionate advocate for gender equality in all careers, from space exploration to athletics, arguing that “good old boy” clubs and politics have stymied women with equal and superior talent from having the same opportunities available to their male counterparts. She has been featured on the Today show, CNN, BookTV, NPR, the BBC, CBS News and many other radio and television outlets around the country. Her columns, articles and op-eds have been published in numerous major metropolitan newspapers, including the New York Times, the Wall Street Journal, the Los Angeles Times, the Chicago Tribune, and the Houston Chronicle. Her radio commentaries have been broadcast on NPR's "All Things Considered" and "Only a Game."

For a sample interview, hear this 2003 NPR piece on the release of her Mercury 13 book, or see this 2007 CBS News interview about the Mercury 13 women receiving honors from the University of Wisconsin.