One of the biggest food challenges astronauts face is menu fatigue. If the overall food intake declines, astronauts are at risk of nutritional deficiency, loss of bone and muscle mass, and
lethargy. In 2013, the NASA Human Research Program funded a project called "
HI-SEAS," an
acronym for “Hawaii Space Exploration Analog and Simulation,” to determine the best way to keep astronauts well nourished during multiple-year missions to
Mars or the moon. A planetary module was built on the Hawaiian island of
Mauna Loa, which simulates the living conditions for astronauts at a future base on Mars. It is believed that the saddle area side of the island resembles a Martian environment. Members of the crew were given items such as shirts, bedsheets, and socks, and were asked to fill out surveys rating qualitative factors like odor, comfort, and appearance. Samples were also taken from the fabrics after use to measure the microbial growth. Research teams from Johnson Space Center also provided exercise and sleep clothing for testing during the mission, in preparation for an International Space Station technology demonstration in 2014. Sierra-Sastre and her colleagues emerged from the space habitat on August 13, ending the four-month simulated mission. ==Astronaut applicant==