(L to r) NASA astronauts Shannon W. Lucid, Margaret Rhea Seddon, Kathryn D. Sullivan, Judith A. Resnik, Anna L. Fisher and Sally K. Ride. These six women were the first official female astronaut candidates, although 12 women underwent some astronaut training in the 1960s.

Thirty-eight years ago this week, NASA announced the names of 35 new astronaut candidates, including the first group of women to officially belong to a new astronaut class.

The picture above shows the six female astronauts in January 1978, at the start of their training period. All six women would eventually fly on at least one mission. In 1983, Sally Ride (far right) became the first American woman to fly in space — 20 years after Russian cosmonaut Valentina Tereshkova became the first woman to orbit the Earth.

While officially recognized as the first female members of an astronaut class, these six were not the first female astronaut trainees. In the early 1960s, another group of women, dubbed the "Mercury 13," were selected for astronaut training. [Major Milestone: 50 Years of Women in Space]

Geraldyn (Jerrie) Cobb was the first woman ever selected for astronaut training, and was later joined by 12 other women whom Cobb nicknamed FLATs, which stood for Fellow Lady Astronaut Trainees, according to NASA. The women were all pilots, and were subjected to the sometimes strange tests that had been devised to evaluate a person's ability to withstand the demands of spaceflight, even though no human had yet flown in space.

Unfortunately, none of the Mercury 13 were ever given the opportunity to fly in space. Two books have been written about the program and the 13 trainees — "Promised the Moon," by Stephanie Nolan, and "The Mercury 13," by Martha Ackermann.

The astronaut class of 1978 (NASA's Astronaut Group 8) was the first new group of astronauts selected since 1969. Ride would become the first American woman in space; Judith Resnik was the first Jewish-American astronaut; Kathryn Sullivan was the first American woman to perform a spacewalk; Shannon Lucid was the first American woman to visit the Mir space station; Sullivan and Ride were also the first two female astronauts to fly on a mission together. Resnik flew her first mission in 1984, and was killed in the Challenger disaster in 1986.

In 2013, NASA announced its newest class of astronauts, consisting of eight candidates, four of whom are women. This is the largest percentage of women in an astronaut class in history.

NASA is currently taking applications for its next class of astronauts.

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