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Everyday science

Cosmic-ray exposure on space missions could cause erectile dysfunction, liquid channels in ice boost frost damage

24 Nov 2023 Hamish Johnston
A space ship
Dysfunction danger: research has shown that exposure to cosmic rays on space voyages could affect male sexual health. (Courtesy: iStock/3000ad)

The latest episode of the Physics World Weekly podcast features an interview with a biomedical ethicist who believes that ethical rules and best practices must be developed for research that is done on humans who take part in commercial spaceflights. Vasiliki Rahimzadeh of Baylor College of Medicine in the US says that people who take part in space missions must be fully aware of the risks.

Now, researchers at Florida State University and Wake Forest University have identified a risk to male sexual health that could occur during deep space missions. The team subjected rats to a simulated flux of cosmic rays. This was similar to what humans would experience on a mission to the Moon or Mars – a journey that would take them away from Earth’s protective magnetic field.

When the rats’ tissues were examined after exposure, the team found evidence of oxidative stress in the creatures’ tissues. In male rats, this impaired blood flow to the erectile tissue in the penis. This suggests that astronauts exposed to a similar flux of cosmic rays could develop erectile dysfunction. The study also suggested that weightlessness would have a similar effect – but not as pronounced.

Persistent dysfunction

This dysfunction is expected to persist when an astronaut returns to the protective cocoon of the Earth – however, the researchers say that the effect could be reduced using antioxidant drugs.

The research was done by Florida State’s Justin La Favor and colleagues, who report their results in The FASEB Journal. You can read more about the research in this article in The Guardian by Ian Sample.

It’s coming on winter here in the northern hemisphere and soon roads, buildings and other structures will be suffering frost-induced damage. Naively, one might think that the expansion of liquid water as it freezes is the main cause of this damage, but according to Physics Magazine’s Katherine Wright it’s much more complicated than that. Indeed, she points out that liquids that contract when they freeze can also cause frost damage.

Instead, it appears that most of the damage is related to how a freezing liquid within a porous material can draw in more liquid – eventually causing the object to swell.

Liquid channels

Wright reports on research done by ice expert Robert Style of the Swiss Federal Institute of Technology and colleagues. The team looked at how channels of liquid water that occur in polycrystalline ice contribute to this drawing-in process – and ultimately to frost damage.

They did this by creating a simple porous material by putting silicone between two glass slides. Pores were created in the soft silicone, which was decorated with fluorescent molecules. This allowed the team to watch the pores swell as the ice drew in more liquid water. They we also able to observe the channels in the ice through which liquid water was drawn in.

The team describes the experiment in Physical Review Letters and Wright’s article is called “Liquid veins give ice its road-wrecking power”.

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