8.5 Wouldn’t sunlight have burned or boiled the astronauts’ faces?

IN A NUTSHELL: No. If so, then it should also do the same to the faces of astronauts who routinely perform spacewalks outside the International Space Station, since sunlight on the Moon is essentially the same as in Earth orbit. But it doesn’t.

THE DETAILS: Some Moon hoax proponents argue that the fiercely strong sunlight on the Moon, unfiltered by the Earth’s protective atmosphere, should have caused intense sunburns or overheating, yet we see photographs and footage of the moonwalkers walking around in full sunlight, sometimes even with their protective visor up (Figure 8-4).

Figure 8-4. Harrison Schmitt’s reflective visor is up in a frame from the Apollo 17 moonwalk TV transmission.

However, the Apollo helmets were designed to protect the moonwalkers adequately both against the ultraviolet solar radiation that causes sunburns and the infrared radiation that causes heating: perhaps not unsurprisingly, these issues had been anticipated and solved during mission planning and suit design and had been tested during spacewalks in the early Apollo flights in Earth orbit, where sunlight is essentially as intense as on the Moon.

There is a common misconception that infrared and ultraviolet protection was provided only by the golden reflective visor and therefore walking around with the visor up would have been impossible or extremely hazardous, as argued for example in Bennett and Percy’s book Dark Moon (on page 102). Actually, this protection was provided both by the clear part of the helmet and by the reflective visor and therefore the astronauts could lift the visor when needed, for example in low-light conditions or for a memorable photograph. The visor was mostly intended to reduce the brightness of the sunlight, much like a pair of oversized sunglasses.

This is the same principle that is used today by astronauts working outside the International Space Station and was used in the past by Skylab, Shuttle and Mir spacewalkers. They, too, are exposed to full sunlight without the shielding of the Earth’s atmosphere, yet don’t get sunburned or overheated; and they, too, often lift their reflective visors with no problems, as shown for example in Figure 8-5.

Figure 8-5. Jerry L. Ross working outside the Shuttle Atlantis (1991). NASA photo STS037-18-032.

Moreover, temperatures measured on the surface have nothing to do with sunburns, as anyone who’s been sunburned during a cool day in the mountains, with snow or ice on the ground, knows all too well. Sunburns are caused by ultraviolet rays in direct or reflected sunlight, not by heat.

The Apollo technical manuals explain that lunar astronauts wore a pressurized helmet (the inner goldfish-bowl transparent enclosure) inside an outer helmet. The inner helmet was made of Lexan, which is very tough and, most importantly, highly opaque to ultraviolet rays. The outer helmet in turn had an inner visor, which filtered ultraviolet and infrared radiation, and an outer visor (the gold mirror-like surface visible in many photographs) that filtered visible light (like mirror shades) to prevent dazzling and provided a further barrier to ultraviolet and infrared rays.*

* Biomedical Results of Apollo, Section 6, Chapter 6, Pressure Helmet Assembly.

Essentially, the moonwalkers didn’t get sunburned for the same reason why you don’t get sunburned if you drive around in your car with the windows up: the transparent material allows visible light to get through but blocks the ultraviolet light that causes sunburns.

Astronauts, both on the Moon and in Earth orbit, often raise their golden visor when they are in shadow and sometimes don’t bother to lower it when they move back into sunlight, but in any case the multiple helmet layers still protect them against sunburn. The worst that can happen to them is that they are dazzled by the bright sunlight.