Both the deep sea and space are difficult to reach and even more difficult to explore. You cant breathe the air, temperatures are extreme, gravity varies, and atmospheric pressure makes survival impossible without protective vehicles. Its part of the reason that these remote terrains are largely left unexplored. Only around 5 percent of the universe and 26 percent of the ocean floor have been visited.Both deep sea travel and deep space travel come with a lot of risks and a lot of preparation, but when it comes to the nitty gritty, how similar are these two remote worlds?Requirements for Deep Sea and Space TravelAccording to DavidKlaus, a professor of aerospace engineering science at the University of Colorado Boulder, the fundamentals and preparation of deep sea and space travel are very similar. Both sea and space require bringing along water, food, and oxygen, as well as the removal of contaminants like urine and feces.The biggest difference between space and the deep sea is that in space youre pressurized from the inside out and under water youve got all the pressure on the outside. And in both cases, you have to maintain the atmosphere with the right amount of pressure, temperature, and humidity.The fundamental functions are, for all practical purposes, the same, but the difference is in how you meet those functions, says Klaus.Read More: What Comes After Oceangate?Exploring the Remote Ends of the Earth and BeyondWhen youre underwater, you can always come up to the surface (even though it might take a few minutes) to resupply, and the same is true of low Earth orbit, where you can resupply with more water, food, and other goods being sent up to the Space Station. If a broken part needs to be repaired, that can happen in low Earth orbit but not in deep space.When youre traveling to deep space, for example, to Mars, the time lag adds another layer of danger. It takes a minimum of six months to fly to Mars, depending on where you are in the Earths orbit.The time lag for communication in deep space can be up to 44 minutes roundtrip, which means if something life-threatening is happening, theres nothing a ground crew can do to help, says Klaus. He adds that this drives the need for autonomous decision-making that you wouldnt necessarily have in low Earth orbit or in the deep sea.The Biggest Risks of Deep Sea and Space ExplorationWe know from the Titan submersible that theres a real risk of implosion when it comes to deep sea exploration. The Titan submersible imploded in June 2023 with five passengers on board. The implosion likely occurred during the vehicles initial descent, killing the passengers instantly. Other risks of deep sea exploration include entanglement on the sea floor and fire in the cabin.By far, the biggest risks in space travel are launch and reentry, when the largest amounts of energy are expended. But theres also the risk of space radiation, which happens beyond the protection of the Earths magnetic field.According to NASA, high-energy galactic cosmic rays and solar storms can harm the body or damage spacecraft. Whats more, isolation from Earth can be risky if an astronaut encounters an accident or has a life-threatening health problem while aboard a spacecraft. Over time, gravity can also be harmful to the body, weakening bones and muscles.While both the deep sea and space offer a new frontier of exploration, each poses its own set of challenges and risks. And with all that goes into exploring these remote worlds, its no wonder that theres still so much more to explore both on Earth and in space.Article SourcesOur writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:United States Coast Guard News. Titan Submersible Marine Board of InvestigationNational Geographic. Expedition Risks and Dangers NASA. Hazard: Space RadiationSara Novak is a science journalist based in South Carolina. In addition to writing for Discover, her work appears in Scientific American, Popular Science, New Scientist, Sierra Magazine, Astronomy Magazine, and many more. She graduated with a bachelors degree in Journalism from the Grady School of Journalism at the University of Georgia. She's also a candidate for a masters degree in science writing from Johns Hopkins University, (expected graduation 2023).