Russia's Bion-M1 biological research satellite, which recently carried rodents, microorganisms and plants on a month-long space flight, successfully accomplished its mission, an official said on Wednesday, despite the death of most of the animals on board.

"The spacecraft did not show any noticeable failures and has accomplished its program in full," said Vladimir Sychev, deputy director of Russia's Institute of Medical and Biological Studies.

Russia launched the Bion-1M satellite, its first biological research satellite since 2007, on a 30-day mission on April 19 to conduct biology, physiology and biotechnology research in orbit. The aim of the study was to help pave the way for future interplanetary flights including Mars missions, according to the Federal Space Agency Roscosmos.

Bion-M1 carried eight Mongolian gerbils, 45 mice, 15 geckos, slugs and snails and containers with various microorganisms and plants.

The satellite's returnable capsule landed on Sunday in the Russian Orenburg Region near the border with Kazakhstan.

Most of the satellite's "space passengers" failed to survive the flight due to technical faults in the spacecraft. The flight proved fatal for all the eight Mongolian gerbils, 39 out of 45 mice, and its cichlid fish. The geckos, slugs and snails were among the lucky survivors.

"We expected that there would be losses. Experiments that pass off ideally do not exist. We expected that up to a half of animals would return," Sychev said.

Stress could have killed the animals, he suggested.

"The transition to zero gravity could have led to stress which could have provoked a conflict in the group," the scientist said, but admitted the fishes' death was due to technical faults.

"Twelve days after [the start of the space flight], the lights went off, algae [in the fish tank] stopped photosynthesizing, oxygen ceased to be released and the fish died," he said, adding the experiment involving the fish had been carried out by German scientists.

The next flight by a Bion satellite could take place in a higher orbit, Sychev said.

"The [current] flight was at an altitude of 575 km [357 miles] where piloted spacecraft fly. We want [a future satellite] to fly to an altitude of 1,000 km. Conditions there will be tougher," he said.

NASA's Bion project science manager Richard Boyle told a news conference in Russia on behalf of all US specialists involved in the project that scientists were overjoyed at the condition of experimental mice and at how promptly they were delivered to Moscow.

NASA's Space Biosciences division said its specialists have already begun cooperative research with Russian scientists.

"By the terms of a contractual agreement with the Russians, the US investigators received tissues from a subset of the mice that were flown," Space Biosciences division chief Sidney Sun said in a statement. "Those mice returned from space in good health. The NASA scientists are conducting their post-flight experimental analysis in laboratories at the Institute of Biomedical Problems in Moscow."