The Biosphere Fire broke out Sunday morning northwest of Oracle Junction and north of metro Tucson, Arizona State Forestry officials said.
The fire’s cause wasn’t immediately known and had spread to about 13 acres by Sunday afternoon before being partially contained.
Crews from the State Forestry, Golder Ranch Fire District and Northwest Fire District worked to keep the wildfire from reaching the Biosphere facility.
State Forestry launched single-engine air tankers to assist with suppression.
No evacuations were ordered due to the fire.
Biosphere 2 was built between 1987 and 1991 as a way to test the viability of closed ecological systems and human life in outer space. The tests were held twice in the early 1990s.
The facility is owned and operated by the University of Arizona in Tucson.
The Associated Press (AP) contributed to this report.
Location of Biosphere 2: