This vista of the Endeavour Crater rim was acquired by NASA's Mars Exploration Rover Opportunity from the southern end of "Murray Ridge" on the western rim of the crater. Source: NASA

Reaching Mars is an immense challenge, as the planet's surface is littered with crashed and defunct spacecraft. But returning from the Red Planet? That requires hurdling another obstacle: harvesting rocket fuel. BoMax Hydrogen and Joi Scientific are two Florida-based start-ups working to prove concepts to produce hydrogen. They each have unique approaches to the process but are both based at the Space Life Sciences Center at NASA's Kennedy Space Center. Hydrogen is typically harvested from fossil fuels and methane. NASA administrator Jim Bridenstine recently spoke to CNBC about the significance of hydrogen on the surface of Mars and the moon. Both planetary bodies have immense amounts of frozen water on the surface, which Bridenstine explained. "That means you've got air to breathe — oxygen. You've got water to drink — H 2 O," Bridenstine said. "But you've also got rocket fuel on the surface of the moon. Hydrogen and oxygen, cracked into its component parts, put into cryogenic form, it's the same rocket fuel that powered the space shuttles."

BoMax Hydrogen's model

Sunshine is the key ingredient for BoMax Hydrogen. The company wants to harness naturally occurring enzymes in visible light to produce hydrogen. Dr. Deborah Maxwell leads BoMax's scientific research team, which has three full-time employees. "We make pure hydrogen because we're using an enzyme," BoMax chief science officer Dr. Deborah Maxwell told CNBC. The BoMax process "isolates the components" and therefore does not require costly filters, Maxwell said. Additionally, she said the lower pressure on the Martian surface makes the process more effective, while the carbon dioxide in Mars' atmosphere does not inhibit its process. "It would be difficult to transport water itself to Mars," Maxwell said. That's why having "access to the water ice on the surface would be advantageous," she said. Instead of having to carry water, "we would transport our feed stock, which is an inexpensive acid," Maxwell said. This feed stock would be transported "in a relativity small amount," Maxwell added. The start-up is in optimization phase of its five-year plan. BoMax expects to scale up its laboratory later this year and then begin manufacturing in 2020. BoMax is funded in part by a $400,000 loan last year from Space Florida, the state's aerospace economic development agency. The company previously raised $1.8 million from individual private investors.

The Joi Scientific approach to hydrogen

Joi Scientific, on the other hand, is looking to create hydrogen from seawater. On Mars that would represent melting down ice and then turning it into hydrogen. The ice on Mars is very salty, like ocean water on Earth. "What we do is very simple: We learned how to take seawater in its raw state ... and we developed a process, which is now patented, that allows us to transition that directly into hydrogen gas at a very prolific rate," Joi CEO Trever Kennedy told the Orlando Sentinel in November. While Joi Scientific's process is different than BoMax's, both companies have had discussions with NASA officials and scientists about the applications of the technology on Mars. Joi Scientific did not respond to CNBC requests for comment.

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