About the TMC Earth Day 5K at Biosphere 2
The course runs entirely on private Biosphere 2 grounds, on roads and paths closed to the public. You start and finish on a grass lawn, then move through gravel, pavement, and a short dirt stretch. The route drops down a steep pitch, climbs back past the main complex, threads through a mesquite forest, and passes a historic ranch house. The mountains are visible for much of it.
Packet pickup happens the evening before at a running shop in Tucson, where you can also pick up bibs for others in your group. Carpooling to the Biosphere is encouraged; parking is in the main visitor lot. After the race, food trucks are set up near the finish along with snacks, drinks, and kids' activities on the lawn.
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TMC Earth Day 5K at Biosphere 2 2026 Results
Going by the 2026 results, this is a decent-sized field, and the spread of finish times is wide, so this is a mostly recreational race rather than one for club runners.
5K Results · 2026
686finishers
19:30winner
41:57median
1:38:10cutoff
Top 3: Nathan Highley (19:30) · Nigel Gruff (20:04) · Brendan Tinoco (20:10)
The TMC Earth Day 5K at Biosphere 2 has been held every year since at least 2020. That is as far back as RunSignup's records for this race go, so it may well be older.
How we calculate these stats: RunSesh calculates these figures from the most recent published results of past editions, sourced from RunSignup. We show aggregates only: field size, winning and median times, and the cutoff. We never publish individual finisher tables. Last updated Nov 12, 2026.
Distances & Start Times
5K4/17/2027 08:30$40
3.1 Miles4/17/2027 08:30$12
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Not sure what to aim for? The 5K pace chart lists the pace for every finish time.
Where to Stay
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