TMC Earth Day 5K
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Event overview
The TMC Earth Day 5K at Biosphere 2 takes place on April 18, 2026, at the Biosphere 2 research facility in Oracle, AZ (32540 S. Biosphere Road, 85623). The event is presented as an inaugural fundraiser for the Biosphere 2 Ocean Reef Lab and includes a timed 5k and a children's 5k. Registration fees listed are $35 for the main 5k and $10 for the children's 5k. All registrants receive free entry to Biosphere 2.
Distances
- 5k Run/Walk
- Children's 5k (open to ages 1-14)
Course, logistics and amenities
The course is described as a rolling 3.1 mile route entirely on Biosphere 2 grounds, with a start and finish on the Great Lawn. Terrain is mostly pavement with a brief dirt section and hilly in parts. Packet pickup is available at The Running Shop on the Thursday before the race and on race day at the Biosphere 2 parking lot. The event offers a souvenir shirt to the first 600 registrants, timed results with a finisher's video, age-group and overall awards, snacks and drinks, and food trucks for purchase. Strollers are allowed; pets are not. Remaining shirts after the event will be available at The Running Shop for a limited pickup period. The event is produced in partnership with Run Tucson and Biosphere 2 / University of Arizona. Visit the organization's website for the most recent information.
