Geckos aboard a Russian mission to study sex in space perished during the flight, and the reptiles returned to the Earth frozen. Mummified remains of the geckos suggest the animals froze to death.

Roscosmos, the Russian space agency, confirmed the death of the animals in a Russian language statement released on their website.

"After extraction of biological objects from the lander... it was found that the fly Drosophila... successfully developed and bred. All geckos, unfortunately, died," Roscosmos managers wrote.

The Photon-M satellite landed in Russia's Orenburg region as scheduled.

Four female lizards and one male were among the lizard crew which perished on the flight. Investigators sent the animals into space in order to study mating habits of animals in space. This research could have provided valuable insight that will be needed as humans begin spending months, or years, in space.

"It's still too early to talk about the geckos' cause of death. According to the preliminary information, it became clear the geckos froze. Most likely, this happened due to a failure of the equipment meant to ensure the temperature of the box with the animals," a member of the Institute of Biomedical Problems (ISTC) said.

Mushrooms and seeds, part of experiments studying radiation and microgravity environments. All of this material has been sent to research centers for further study.

Investigators are researching the remains of the geckos, in order to determine the exact time and cause of death. A commission will soon be appointed in order to manage research into the accident.

Russian space managers lost track of the spacecraft and its lizard crew near the end of July 2014, but re-established communications a few days later. The initial fear among mission planners was that loss of life support would cause the animals to starve to death within three months if control were not regained. Loss of communications with the craft should not have affected climate control aboard the vehicle, according to the ISTC.

Geckos have lower metabolisms which should have allowed the animals to survive at lower-than-normal temperatures. Feet of the lizards, which allow the animals to hang on walls and ceilings, should have protected the creatures from the effects of microgravity.

An international research flight in 2007 launched newts, gerbils, butterflies, snails and other organisms into space.

Russia has seen a series of recent setbacks to their space program. Since May, a pair of rockets has crashed and the launch of an Angara rocket launch was cancelled.