Six members of the advocacy group PETA held a small protest outside of NASA headquarters this morning, in response to radiation experiments the space agency is planning to conduct on monkeys.

The radiation experiments will be performed on squirrel monkeys to test the potential effects of long-term space missions, such as a trip to Mars.

A media alert sent by the group said that protestors would be wearing monkey masks while locked in small cages and carrying signs that read, "No Tax $ for Animal Abuse," and "Stop Radiation Tests on Monkeys."

NASA spokesman Morrie Goodman said that NASA considers the research necessary to their mission and their responsibility to ensure the health of their astronauts. For possible future long-term missions, "space radiation is one of our most important problems," he told SPACE.com.

Goodman the research animals would be cared for in accordance with appropriate guidelines. "Our welfare concerns are for both animals and humans," he said.