TMC Earth Day 5K at Biosphere 2

2027 Registration Open

2026 RACE DAY THANK YOU!   Click here for the first post-race email to participants.

Thank you for being part of this wonderful event!  We hope you had a great time out there today!

Results are at this race page or at www.roadrunnerracetiming.com . If you did not pick up your award, you can snag it at The Running Shop (3055 North Campbell) starting on Saturday afternoon at 3:0pm Remaining t-shirts are at The Running Shop (currently, sizes large and extra large), as are the handful of pre-purchased medals that did not get picked up.  Please bring proof of purchase if you want to snag your medal.

APRIL 16 UPDATE: We've reached our cap and have sold out of the souvenir medals, so we do not have any more available to purchase.  If you register after April 16th, please note that you cannot pick up a shirt before the race.  If there are any remaining shirts after the pre-race packet pickup, any leftover shirts will only be available AFTER the race, on a first-come, first-served basis at the Run Tucson tent.

April 14 Update: All race details are on the various pages on this registration site, but you can also click here for the final pre-race email to all participants with race weekend details.

Looking for a way to celebrate Earth Day? Join us at Biosphere 2 for a 5k run and walk, entirely on the grounds of the famed facility.  Whether you're a seasoned athlete or just looking for a fun way to get some exercise, you're sure to enjoy yourself at the world-famous Biosphere 2.

Clear your schedule and join us at the April 18th TMC Earth Day 5k, where you can walk or run the hidden Biosphere 2 backroads, nestled at the base of the majestic Catalina Mountains, north of Tucson. The rolling 3.1 mile course is perfect for racing and walking, with gorgeous desert and mountain views and a start and finish on the beautiful Great Lawn.

After the 5k, you can relax, listen to music, snag some food, and enjoy other fun activities, so make sure to stick around to socialize and have some fun.

Pricing: $40 for the $5k includes race entry, souvenir shirt, free Biosphere 2 entry (special price of $10 for children 14-and-under includes the 5k race and entry to Biosphere 2, but no souvenir shirt).

Ongoing Tours of the Biosphere 2:  Explore a 3.14-acre living laboratory where cutting-edge research unfolds across diverse ecosystems—including the Landscape Evolution Observatory.

All registrants receive free entry to the Biosphere 2 informative tour of the renowned research facility, with an exclusive peek into the inner workings of the Biosphere 2, a wild world of wetlands, rainforests, grasslands, fog deserts, and the big blue ocean. It's like a backstage pass to nature's superstar habitats!

All registrants can visit Biosphere2 on their own -- no need for a formal tour! All non-running guests can purchase Biosphere 2 admission for the discounted rate of $10 (before 8:30 am) and all children under 12 are free.

The TMC Earth Day 5k is raising funds for the Ocean Reef research project, learning how to grow ocean reefs in a changing climate.   See details and donate here.

What you get:

Souvenir shirt to first 750 registrants

Timed 5k with finisher's video

Age group and overall awards courtesy of The Running Shop

Free entry to the world-famous Biosphere 2

Snacks and drinks

Food trucks with yummy post-race food for purchase

Children's activities

Schedule

Thursday, April 16 4:00 - 6:00 pm Packet pickup and in-person registration at The Running Shop, 3055 North Campbell, Tucson T-shirts to the first 750 registered, sizing and style on a first-come, first-served basis. Yes: you can pick up the number/shirt of other people Yes: you can shop for cool goodies at The Running Shop. Yes: It may be crowded, so please be nice to everyone Yes: Be sure to take pins and pin your number on the front of your racing shirt.

Saturday, April 18 at Biosphere 2, 32540 S Biosphere Rd, Oracle, AZ 85739 Please consider carpooling. Please park in the main parking lot at the Biosphere 2.  Please follow the directions of the Biosphere 2 staff on hand.

7:15-8:15 am Race day registration and packet pick up in the parking lot by the front entrance at the Biosphere 2.  Pick up your race shirt and colorful race bib number. 8:30 am Start time for TMC Earth Day 5k Run/Walk 8:30 or so: Food trucks, with snacks and drinks available for purchase 9:45 am Free Kids Dash on the Great Lawn 10:00 am Awards, courtesy of the Running Shop. Remaining shirts available to late registrants, first-come, first-served. 10:15 Event wrap-up Tour the Biosphere 2: All registrants can visit Biosphere2 on their own -- no need for a formal tour! All non-running guests can purchase Biosphere 2 admission for the discounted rate of $10 (before 8:30 am) and all children under 12 are free. Post-race: If you can't make the race weekend activities, please note that any remaining shirts will be brought to the Running Shop and available for pickup between April 21 - May 15. To get the size you want, pick up your shirt in advance.

Nice words from 2024 runner Dale: It’s important to me to thank the people who help make Tucson the awesome community it is! Saturday’s Earth Day was fabulous! I’ve been fortunate to attend all the races you’ve had out there! Just the view and space is incredible and what a gift to be able to “struggle” up the hills while taking it all in!   Thank you so much for all you and your staff/team do.

Nice words from 2024 runner Louise: Wow!! Are you guys efficient or what?  Thanks so much for the quick turnaround with results and, again, for organizing and running a great event.  The water stop was especially appreciated on a hot day. (And even if we were running short of time, the announcer was funny and added an enjoyable element to announcing the winners.)

Bring the Kids!   Special $10 price for children 14-and-under in the 5k: includes race number, timing, and entry to Biosphere 2, but no t-shirt.

Running strollers are welcome, but be mindful of the steep hills and be sure to have the leash attached!

After the 5k, the little ones can enjoy the  free Kid's Dash & Kid's Zone activities.

Do Good! This event raises funds for the world-renowned Biosphere 2's Ocean Reef Lab.

Terrain: mostly pavement, with a brief dirt section

Difficulty: hilly in sections

Weather: 50's - 70's

Differently Abled: Yes, be mindful of hills and dirt road

Pets Allowed: No

Want Training Advice? Contact RRCA-certified running coach Tia Accetta at tia@runtucson.net.

This event is a partnership between Run Tucson & the Biosphere 2, the University of Arizona

Questions? Contact Race Director Randy Accetta at randy@runtucson.net .