The effects of cosmic rays on astronauts: the Light Flash phenomenon

1 11 2011

Cosmic rays cannot turn a man into a rocky goliath or into a human torch, neither give a man invisibility or a stretching  body. Nevertheless we must acknowledge Stan Lee’s intuition that cosmic rays could interact and have actual effects on human biology.

Before detailing what cosmic rays are and where they come from, I would like to introduce some effects they provoke and introduce the scientific rationale that’s behind ALTEA investigation.

During Apollo 12 mission (1969), there was an experiment called “the Apollo helmet dosimetry experiment”, during which the signs of cosmic ray passage on an astronaut helmet were very evident.


ALTEA studies the effects of cosmic rays on central nervous system and in particular the Light Flash phenomenon. Currently light flashes are the only way that humans have to actually see elementary particles without any instrument or detector. In 1952 the physicist Cornelius Tobias predicted that cosmic rays could interact with astronaut visual system to generate anomalous perceptions of light (without the effective presence of light) . In 1969, during Apollo 11 mission, Buzz Aldrin reported the first experience of these flashes after their eyes had become adapted to the low light in the cabin. He talked about strange flashed of multiple shapes and dimensions.


After this first report, the astronauts of the following lunar missions were informed about the phenomenon and started dedicated observations. During the last lunar missions, Apollo 16 and 17, the ALFMED emulsion detector studies the correlation between the light flash perceptions and the cosmic rays.


ALFMED results showed that high energy charged particles composing cosmic rays were the effective cause of the light flashes. The interaction mechanism remained unexplained. Systematic studies on Light Flashes were carried on during the Skylab (1974) and the Apollo-Soyuz (1975) missions. In the meantime some scientist volunteered to expose themselves to low intensity particle beams to study the phenomenon in controlled conditions. Light Flashes could be reproduced by various particles passing through the eyes.

Light Flashes are highly subjective: some astronauts are particularly sensitive and can observe the phenomenon even in bright environment while others never observed any. Some astronauts are so annoyed by these flashes that cannot fell asleep. There are different shapes of flashes: stripes, multiple tracks, stars, explosions, etc..


When it’s time to link the LF phenomenon to the physics mechanisms originating them a lot of problems arise. It is needed to correlate observations from electronic detectors with astronaut sensations. The importance of these studies is given by the fact that LF could be symptoms of a wider family of more complex neuro-physiologic effects that are still hidden.

Studies on LF continued during the 90’s onboard MIR space station with the Sileye project. In the frame of this project almost 50 observation sessions were completed between 1996 and 2000 by 10 astronauts that observed more than 200 LFs. Sileye derives its name from Silicon Eye, the particle detector coupled with an helmet used for the observations. The cosmonaut wears the helmet in a dark environment and pushes a button whenever he observes a flash; in the meanwhile the particle detector measures the energy of all nuclei passing through it.

clip_image012 Cosmonaut Sergei Avdeev with Sileye-1 detector during a LF observation session onboard MIR.     clip_image014 Sileye-2 before being launched to MIR: aluminum box (on left side) contains the silicon telescope, while the yellow mask on the right is used to test dark adaptation of the astronaut.     clip_image016 
Cosmonaut Sergei Avdeev with Sileye-2 detector during a LF observation session onboard MIR.

Sileye program continued on ISS with the Alteino-Sileye3 detector, that is the link between the Sileye project and the ALTEA program. Alteino was brought onboard the International Space Station during Marco Polo Mission in 2002. First measurements were carried on by the Italian astronaut Roberto Vittori. Alteino device returned back to Earth in 2010.

Alteino-Sileye3 detector in the PIRS module of the ISS.
Light Flash observed on MIR. The increasing of LF observations at high latitudes and over the South Atlantic region is caused by different components of cosmic rays: galactic and trapped cosmic rays.

Coming soon: Radiation environment in Earth orbit.

Previous posts:
Cosmic rays and human exploration of space
ALTEA- An Italian experiment onboard the International Space Station

Further readings and sources:
Cosa sono i Light Flash (in Italian)
Light flashes (in Italian)
How can astronauts see stars with their eyes shut


Cosmic rays and human exploration of space

30 10 2011

Discovery of cosmic rays

In the end of the XIX century physicists, studying gas conductivity with electroscopes, discovered that they slowly discharged despite being isolated from radiation sources. In 1901 Wilson suggested that gas ionization could be due to radiation coming from sources external to earth atmosphere and with high penetrating power.

Investigations by Theodore Wulf (1907) and Domenico Pacini (1907-1910) demonstrated that radiation was not decreasing when moving away from earth surface and sometimes it was even increasing, strengthening the extraterrestrial hypothesis.

On August 12th 1912, Victor Hess measured radiation with two hermetically sealed ionization chambers flying on a balloon up to 5350 m. He observed that ionization increased starting from 1500 m and doubled at about 5000 m. Hess concluded that ionization was due to high penetrating radiation coming from outer space and in 1936 he won the Nobel prize for Physics.

The name of cosmic rays was proposed by Robert Millikan when in 1925 he started studying this kind of radiation. He thought that they were mainly composed by gamma rays.

Unlike Millikan, Bruno Rossi and Arthur Compton assumed that cosmic rays were composed by charged particles: further measurements showed that this hypothesis was correct. Radiation distribution was in fact related to magnetic latitude as one would expect from charged particles interacting with earth magnetic field. This measurement was performed in 1927 by Clay during a trip from Amsterdam to Java. Clay observed that CR intensity decreased approaching equator.

In 1930 the Italian physicist Bruno Rossi observed that, if particle charge was positive, cosmic rays would come preferably from east direction. This effect was measured in 1933 by two American groups, T.H.Johnson and L.Alvarez with A.H.Compton.

Human exploration of space

About thirty years later, on October 4th 1957, from Baikonur cosmodrome, in the current Kazakistan, the first artificial satellite was launched: the Sputnik. The space race was started.

Only four years later the first man was flying in space: the russian cosmonaut Yuri Gagarin completed one orbit around the earth with the Vostok 1 spacecraft. He landed after 88 minutes. It was April 12th 1961.

United States replied with Alan Shepard launch on May 5th of the same year, but this was only a sub-orbital mission. To see the first american astronaut in orbit we have to wait until February 20th 1962. In the Mercury 6 mission John Glenn with Friendship 7 spacecraft completed three orbits for a total time of 5 hours.

On June 16th 1963 Russians launched the first woman cosmonaut, Valentina Tereskova, with Vostok 6 spacecraft. She completed a mission of three days in orbit.

After Mercury project, that consisted of single astronauts, Americans started Gemini project with a crew of two astronauts. The Gemini project was composed by 10 flights and 20 astronauts in orbit between 1965 and 1966.

In March 1965 the russian cosmonaut Alexei Leonov performed the first spacewalk (12 minutes) during Voskhod 2 mission. Few months later, during Gemini IV mission, also an american astronaut completed an EVA (Extra Vehicular Activity) for a total time of 22 minutes. For the first time ever, a man was exposed to space environment being protected by his suite only.

Effects of cosmic rays on human being

In 1964 there was the first evidence of cosmic rays interacting with human beings. Four astronauts, Reed Richard, Ben Grimm, Susan Storm and Johnny Storm were launched on an experimental rocket to a space mission. But during the navigation they were hit by cosmic rays that deeply modified their bodies.

Reed Richards started to stretch because his cells became similar to rubber.

Benjamin Grimm became a rocky monster with the streght of a thousand men. During the transformation Susan said: “Ben , you are turning into a thing…” The Thing was born.

Johnny Storm body started to burn and being lighter than air he started to fly. He could even launch fireballs: he was called the Human Torch.

Susan Storm started to fade. She will be the Invisible Woman. Susan could also create an invisible force field, useful to protect the four from the enemies.

From the mind of Stan Lee the Fantastic Four were born.



Coming next: The effects of cosmic rays on astronauts: the Light Flash phenomenon

Previous posts:

ALTEA- An Italian experiment onboard the International Space Station

I Fantastici 4
Origin of the Fantastic Four
Humble beginnings