(CNN) Astronauts put their lives at risk every time they are launched into space in the name of research, push the boundaries of the human body by living in zero gravity and plummet back to Earth in what retired astronaut Scott Kelly has described as a "giant fireball." But NASA doesn't have the authority to provide retired astronauts with health care.

The wider issue of astronaut health made an appearance on Capitol Hill this week as former and current astronauts and other officials made the case for legislation to care for what several representatives called "modern heroes."

As Rep. Eddie Bernice Johnson, D-Texas, noted during the hearing, those in the U.S. military receive lifetime help and support, but astronauts don't. Though 60% of astronauts are either current or retired military members and their care is processed through the Department of Veterans Affairs, that does not account for all current and former astronauts, according to NASA Chief Health and Medical Officer Dr. Richard Williams.

The proposal would allow NASA to perform annual medical monitoring and provide diagnosis and treatment for active and former astronauts, as well as to gather long-term health data to lower the risk for future spaceflight missions, according to Williams.

"The proposed legislation on astronaut health will not only help us learn more about the impacts of human spaceflight but will also serve to protect the health of those who push the boundaries in the name of exploration on behalf of our nation," Kelly said.

Kelly and Williams were joined Wednesday by Chief Astronaut Chris Cassidy and former astronaut Michael Lopez-Alegria before the House of Representatives Subcommittee on Space in a hearing titled Human Spaceflight Ethics and Obligations: Options for Monitoring, Diagnosing, and Treating Former Astronauts . They were supported by Jeffrey Kahn, chairman of the Committee on the Ethics Principles and Guidelines for Health Standards for Long Duration and Exploration Spaceflights.

The astronauts shared their personal experience with spaceflight and its effects on their health and that of their colleagues to help the committee evaluate the impacts.

The health risks of spaceflight

Though it's well known that astronauts face some of the greatest dangers during launch and re-entry, the health hazards they experience during spaceflight also pose immediate and long-term threats.

Especially for astronauts experiencing six-month stays on the International Space Station, exposure to radiation, carbon dioxide, excessive noise, toxic materials and weightlessness in zero gravity can leave lasting impacts.

Astronauts and researchers have identified issues like visual impairment, musculoskeletal injuries, bone density loss, muscle atrophy, vulnerable immune systems and post-mission renal stones during and after spaceflight. They are at a higher risk for cancer, degenerative tissue disease and possible central nervous system effects later in life.

After flying four missions that totaled 520 days in space, Kelly has been outspoken about the way he felt in March after completing a year in space. He described to Congress the quick stiffening of his muscles, the swelling in his legs due to the fluid shift of being in zero gravity, a hives-like rash after not touching anything on Earth for a year and persistent flu-like symptoms.

The astronauts and researchers are concerned about effects of space on the human body that we don't yet know or understand. Many times, astronauts don't encounter health issues until years after returning to Earth. Some have developed cataracts and bone fractures years later.

Currently, NASA has the Lifetime Surveillance of Astronaut Health program in place for monitoring former astronauts. The voluntary program includes limited annual health status evaluations at the Johnson Space Center Medical Clinic in Texas. Should any issues be found during the evaluation, NASA is authorized only to recommend that the former astronaut follow up with their personal health care provider, who probably has little or no understanding of space-related health issues, according to Williams.

"Statistical analysis shows that astronauts who fly to and from the ISS aboard a Soyuz spacecraft and spend six months there have a threat of mortality comparable to those of U.S. infantry combatants on D-Day and New York City firefighters on 9/11," said Lopez-Alegria, who is also president of the Association of Space Explorers.

He also cited how dedicated occupational medical programs for surveillance, diagnosis and treatment of health consequences exist for nuclear workers with the Department of Energy, the Department of Defense and the civil nuclear power industry. The Department of Energy provides a Former Worker Medical Screening Program at no cost to all its former federal, contractor and subcontractor workers who may be at risk for occupational diseases, he said.

The solution and how data will get us to Mars

NASA is allowed to provide medical care and treatment for active astronauts, including routine occupational health and preventive exams, customized monitoring based on their exposure and data analysis to mitigate or control health risks.

Williams said he believes this could be applied to former astronauts and expanded in such a way that services could be provided outside Texas for those who aren't able to travel due to their medical conditions.

The national Institute of Medicine has made such recommendations in three studies from 2001, 2004 and 2014. In its 2014 study on health standards for long-duration and exploration spaceflight, the institute recommended that "the agency should also provide preventive long-term health screening and surveillance and lifetime health care to protect astronaut health, support ongoing evaluation of health standards, improve mission safety, and reduce risks for current and future astronauts."

Data collection is an integral part of reducing those risks for current and future astronauts, the astronauts said.

With the voluntary surveillance program that's now in place, which has limited funding, only 60% of the 250 living former astronauts participate. This presents an incredibly limited data set for people who have been in space. Expanding the scope of care NASA can provide to former astronauts would increase participation to at least 80% or so, Williams said.

What we learn about the health of current and former astronauts will inform spaceflight possibilities, including deep-space missions to Mars.

"Radiation is and most likely will continue to be the major limitation to human space exploration for the foreseeable future," Lopez-Alegria said.

Using current data, NASA has developed countermeasures to mitigate bone and muscle loss, like having astronauts work out for two hours a day while living on the ISS. More research could help the agency discover ways to shield astronauts from radiation and other risks during deep-space missions.

And we've only scratched the surface of known risks to astronauts. Deep space will expose them to more, and health data from former and current astronauts can better prepare and inform future missions, Kelly said.

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Kelly also pointed out that NASA's research can lead to treating similar ailments on Earth like osteoporosis, muscle-wasting diseases, high blood pressure, glaucoma and brain diseases. Some existing FDA-approved treatments are a direct result of space-based research.

"The proposed legislation on astronaut health will not only help us learn more about the impacts of human spaceflight but also will serve to protect the health of those who push the boundaries in the name of exploration on behalf of our nation," Kelly said.

The subcommittee now has two weeks to pose questions to Kelly and the rest of the witnesses.