International space station - Reuters - May 23 2011
The International Space Station is seen with the docked space shuttle Endeavour in this photo provided by NASA and taken May 23, 2011. Photo by Reuters
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Three Israeli experiments to examine the impact of space travel on human health were among the various studies and tests conducted on the American space shuttle Endeavor's recent mission to the International Space Station. Endeavor returned from its latest space mission - the last for this particular space orbiter - on June 1.

Material from two of the Israeli experiments returned to earth with Endeavor. The third was left on the International Space Station, and will only be retrieved by astronauts aboard the space shuttle Atlantis, on July 20. That space shuttle's journey will mark the end of the current U.S. space shuttle program.

This was the first time an Israeli experiment had been sent to the International Space Station, as opposed to the space shuttle, noted space physician Eran Schenker of the Herzliya-based Fisher Institute for Strategic Air and Space Studies.

The Israeli experiment currently on the space station will gauge the effects of cosmic rays on telomeres, a part of cell chromosomes that regulate the life of the cell. Telomeres serve to protect the integrity of cell DNA, and unlike other DNA, when cells divide, telomeres do not replicate themselves, but instead become shorter. When sufficiently reduced in length, telomeres cause the cell to die.

In addition to other dangers posed by cosmic rays, researchers believe that it damages telomeres and shortens the lifespan of cells in space. The Israeli experiment has sparked special interest in light of the importance of telomeres in regulating the biological clocks of cells. The 16 days of the Endeavor's last mission was insufficient to measure the effects of radiation on telomeres and this was why the experiment was left on the International Space Station, Schenker explained.

Coping with the various hazards of cosmic rays are a major challenge for space agencies seeking to send human beings deeper into the solar system.