TMC Earth Day 5K
Always double-check with the organizer's website! This page may contain affiliate links.
TMC Earth Day 5K at Biosphere 2
The TMC Earth Day 5k takes place on April 18, 2026, on the grounds of Biosphere 2 in Oracle, Arizona. The event lists a main 5k run and walk and a children's 3.1 miles entry option; the children's entry runs in the same race as all participants and can be entered at a reduced price that does not include a shirt.
The course is a rolling 3.1 mile loop on the Biosphere 2 property with mostly paved surfaces and a brief dirt section. The route includes hilly sections and offers desert and mountain views, with the start and finish located on the Great Lawn. Strollers are allowed. Pets are not allowed. The event notes accessibility is available but requests awareness of hills and dirt road conditions.
All registrants receive entry to Biosphere 2 and may take self-guided visits or join ongoing tours of the research facility, which includes multiple ecosystems and the Landscape Evolution Observatory. Amenities listed for participants include a timed 5k with finisher video, souvenir shirts for the first 750 registrants, age group and overall awards, snacks and drinks, food trucks, and children's activities including a Kids Dash and Kid's Zone.
The event raises funds for the Ocean Reef research project and is presented in partnership with Run Tucson, Biosphere 2, and the University of Arizona. Visit the organization's website for the most recent information.
