Greg Toppo

USATODAY

Six scientists who lived for a year inside a dome on a Hawaiian mountain emerged Sunday from the experiment, meant to simulate a trip to Mars.

The NASA-funded study was the second-longest of its kind, following a Russian mission that lasted 520 days.

During the simulation, run by the University of Hawaii, the scientists could go outside only while wearing spacesuits as they worked to help researchers understand how the isolation of a deep space mission would impact humans.

The mission participants — Carmel Johnston, Christiane Heinicke, Sheyna E. Gifford, Andrzej Stewart, Cyprien Verseux and Tristan Bassingthwaighte — lived together for 12 months with limited contact from friends, family and the outside world. The crew exited the habitat around 9 a.m. local time (3 p.m. ET), NBC News reported.

The experiment took place on isolated, rocky Mauna Loa, on the island of Hawaii, the state’s largest island. It was part of the HI-SEAS (Hawaii Space Exploration Analog and Simulation) program, the fourth and longest HI-SEAS mission to date, NBC reported. The first, in 2012, lasted just short of four months.

As the six emerged Sunday, on an overcast day, Verseux could be heard saying, "We were hoping for some sun."

Kim Binsted, HI-SEAS’ principal investigator, told The Associated Press that the researchers were looking forward to getting into the ocean and eating fresh produce and other foods that weren't available in the dome.

During the experiment, participants were almost entirely self-sufficient, using a limited supply of food and other necessities. Even routine communication between the crew and the outside world was subject to a 20-minute delay to mimic the limitations of communicating with deep space.

The crew members said they faced several challenges, including the necessity of rationing limited resources and a plumbing malfunction that left them bathing with buckets for two weeks.

HI-SEAS plans to send crews into the simulation for eight months at a time in 2017 and 2018, NBC reported, and is looking for applicants.

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