HOUSTON -

A group of researchers is building a menu for a planned NASA mission to Mars in the 2030's, mixing and tasting the vegetarian concoctions they hope to send with the astronauts.

Lockheed Martin senior research scientist Maya Cooper says the menu must keep the crew of six to eight astronauts physically and mentally healthy for the life of the mission.

She says the biggest challenge is the distance. It would take six months to get to Mars, 18 months on the surface and then another six months to return.

The researchers are considering having the crew care for a "Martian greenhouse" and prepare their own food. They might also send food that is pre-packaged and prepared on Earth.

The project is costing about $1 million annually.