Possible Mars Mission 'Showstopper': Vision Risks for Astronauts

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Space.com
Possible Mars Mission 'Showstopper': Vision Risks for Astronauts
By Mike Wall, Senior Writer
April 08, 2014 07:00am ET

Mars may possess a stark and austere beauty, but a manned Red Planet mission will likely not be easy on the eyes.

Recently, scientists have begun realizing that spaceflight can cause serious and perhaps permanent vision problems in astronauts. NASA researchers are working hard to understand the issue, which could present a major hurdle to mounting manned missions to Mars and other faraway destinations.

"This is one that we don't yet have a good handle on, and it can be a showstopper," Mark Shelhamer, chief scientist for the NASA Human Research Program at Johnson Space Center in Houston, said last week during a presentation with the agency's Future In-Space Operations (FISO) working group.

Another Peril of Microgravity

The human body suffers in the microgravity environment of space. For example, without effective countermeasures — i.e., vigorous weight-bearing exercise — astronauts' muscles atrophy and their bones shed calcium, becoming more and more brittle over time.

Spaceflight can also affect the eyes. Researchers have known this for decades, but they're just now beginning to appreciate the gravity of the situation.

"Over the last 40 years there have been reports of visual acuity impairments associated with spaceflight through testing and anecdotal reports," a 2012 NASA report about spaceflight-related vision problems states. "Until recently, these changes were thought to be transient, but a comparison of pre- and postflight ocular measures have identified a potential risk of permanent visual changes as a result of microgravity exposure."

The problem is not confined to just a few isolated individuals, either. Postflight examinations performed on about 300 American astronauts since 1989 showed that 29 percent of space shuttle crewmembers (who flew two-week missions) and 60 percent of International Space Station astronauts (who typically spend five or six months in orbit) experienced a degradation of visual acuity, according to a report published this year by the U.S. National Academy of Sciences.

Though they don't yet know for sure, researchers think these eye problems stem primarily from an increase in pressure inside the skull. Cerebrospinal fluid flows into the head more in space than it does on Earth, where gravity pulls it down toward the lower body.

"That increased pressure of cerebrospinal fluid, which surrounds the brain, works its way down the sheath of the optic nerve and pushes on the back of the eyeball," Shelhamer said during his FISO presentation.

Loss of visual acuity and other problems can result from this scenario, which researchers call VIIP (Visual Impairment/Intracranial Pressure). And the issues can persist for long periods after astronauts touch down, Shelhamer said.

"This has really got our attention," he said, "because when you start talking about affecting the vision of astronauts, who are in high-performing, demanding environments, and those vision changes do not always correct themselves after weeks or months back on Earth, so you might be causing permanent damage — this is really a serious problem for us."

Adding to the concern, Shelhamer added, is that researchers don't yet know if VIIP-related problems will level off or intensify for astronauts who spend more than six months off the planet. A yearlong mission to the space station involving one NASA astronaut and one cosmonaut, which is scheduled to blast off next year, could help in this regard.

More information about the effects of long-term spaceflight is crucial for NASA, which aims to get astronauts to the vicinity of the Red Planet by the mid-2030s. With current propulsion technology, roundtrip missions to Mars will require a year of spaceflight at the minimum, in addition to any time spent on the planet's surface.

What Can Be Done?

Researchers are still working to understand exactly what's causing the vision issues. For example, the elevated levels of carbon dioxide found within the space station may be a significant factor in the VIIP phenomenon, Shelhamer said, since high CO2 concentrations are known to increase production of cerebrospinal fluid and dilate blood vessels in the brain.

Speculating on how to prevent or mitigate astronauts' vision problems may thus be a bit premature at this point. But if the main VIIP hypothesis pans out, artificial gravity would be an obvious countermeasure, Shelhamer said.

Artificial gravity can be induced by spinning a spacecraft — or parts of it.

"You could have people sleep while they're spinning, so then they just get eight hours or so of artificial gravity," Shelhamer said.

Artificial gravity would also help mitigate bone loss and muscle degeneration, reducing the need for exercise and potentially freeing up more time for astronauts to perform scientific experiments or do other work during long space missions, advocates say.

[Buster's Uncle]

NASA Mulls Ethics of Sending Astronauts on Long Space Voyages
SPACE.com
by Miriam Kramer, Staff Writer  13 hours ago



This still frame from a video illustrates the danger of overexposure to radiation for astronauts on a mission to Mars.



NASA should set up a clear set of ethical rules regarding the health of astronauts on long-duration spaceflights — such as a trip to Mars — in the near future, according to a panel of health and ethics experts.

As it stands now, astronauts on a roundtrip mission to Mars would experience a level of radiation exposure that violate at least one of NASA's existing health limits, according to previous Mars mission studies. Such a trip to the Red Planet would expose astronauts to enough radiation to increase their lifetime risk of developing fatal cancer by more than 3 percent, a health limitation imposed by NASA.

While NASA should not relax its current health standards for long-duration space travel, the agency should consider developing ethics guidelines on when exceptions to those standards should be made for deep-space voyages, a report from the National Academy of Science's Institute of Medicine committee released on April 2. [The Human Body in Space: 6 Weird Facts]

Those exceptions could be vital for missions that send humans to Mars, an ultimate goal for NASA, or to send astronauts on ultra-long missions to the International Space Station. Currently, astronauts spend about six months on the space station. A NASA astronaut and Russian cosmonaut are due to fly a one-year trip to the station in 2015.

"From its inception, space exploration has pushed the boundaries [of human endurance] and risked the lives and health of astronauts," Jeffrey Kahn, chair of the IOM committee, said in a statement. "Determining where those boundaries lie and when to push the limits is complex. NASA will continue to face decisions as technologies improve, and longer and farther spaceflights become feasible. Our report builds upon NASA's work and compiles the ethics principles and decision-making framework that should be an integral part of discussions and decisions regarding health standards for long-duration and exploration spaceflight."

Some of the risks astronauts face during long-term spaceflights include vision impairment, heightened cancer risk due to radiation exposure and bone loss from the microgravity environment, the report said. There may also be risks that are "unforeseeable" before the mission begins, the report added.

The first step in this ethical framework should be deciding if a long-term space mission's value is worth the potential risk to the astronauts performing it. If a mission is considered "ethically acceptable," then NASA officials should develop a system for granting the exception. The IOM report does not comment on the value of specific missions.

According to results from NASA's Mars rover Curiosity, a 180-day flight to the Red Planet followed by a 600-day stay on Mars and a 180-day flight back to Earth would expose astronauts to about 1.01 sieverts (radiation units). Some researchers consider that level of radiation manageable, however, it would violate NASA's current standard that caps the excess cancer risk for a given astronaut at 3 percent.

These ethical principles should help guide mission decisions, according to a statement from the IOM. The principles from the IOM were detailed as follows in a statement:
Avoid harm by preventing harm, exercising caution, and removing or mitigating harms that occur;
Provide benefits to society;
Seek a favorable and acceptable balance of risk of harm and potential for benefit;
Respect autonomy by allowing individual astronauts to make voluntary decisions regarding participation in proposed missions;
Ensure fair processes and provide equality of opportunity for mission participation and crew selection;
Recognize fidelity and the individual sacrifices made for the benefit of society, as well as honor societal obligations in return, by offering health care and protection for astronauts during missions and over the course of their lifetimes.

"Astronauts put their lives and health at great risk for their country and humankind," Kahn said. "Our report builds on NASA’s work and confirms the ethical imperative to protect astronauts' health, while fulfilling the agency's mission of exploration."

NASA should also inform astronauts of the known risks of a long-duration mission every step of the way — before launch, during the mission and after the astronauts return to Earth, IOM officials said in the report.

NASA funded the IOM report. You can obtain a copy of the full report, "Health Standards for Long-Duration and Exploration Spaceflight: Ethics Principles, Responsibilities and Decision Framework," here: http://www.nap.edu/catalog.php?record_id=18576


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