Five lusty lizards aboard Russia’s infamous “gecko sex satellite” have all died, according to Roscosmos, the Russian Federal Space Agency.

These poor geckos had it pretty rough from the start—first they were rudely sent into orbit and expected to do the dirty deed whilst being observed by scientists back on Earth, then communication was lost for seven days which left us thinking they’d never make it home. Despite control being regained, our worst fears came true: the lizard cosmonauts died before landing on Monday.

While the cause of death is currently only speculation, officials have said “with confidence that they died at least a week before the landing because their bodies were partly mummified,” according to news agency ITAR-TASS.

It is thought that they may have died of hypothermia after the satellite’s heating system malfunctioned; however, it is also possible that other pieces of equipment could have failed and ultimately caused their demise.

The geckos were on board the Photon-M4 satellite with various other organisms including fruit flies and silkworm eggs. Researchers were hoping to investigate the effect of weightlessness on reproduction and development. The six-tonne satellite was also being used to investigate the growth of semiconductor crystals in microgravity.

Photon-M4 was launched back in July and was meant to remain in orbit for two months, but it returned to Earth after just 44 days.

Despite the malfunctions that resulted in the untimely death of the geckos, the fruit flies managed to survive and successfully bred on board.

Godspeed space sex geckos, we will always remember your sacrifice in the name of science.

[Via BBC News, Roscosmos and ITAR-TASS]