Russia’s “space ark” returned to Earth on Sunday after a month spent in orbit roughly 345 miles above the planet’s surface, though with fewer critters than it left with.

Of the 45 mice sent into orbit, the majority did not survive the journey, according to Phys.org. However, the news outlet explains, as the scientists overseeing the experiment told Russian media, this was to be expected.

What was not expected was the failure of certain equipment that led to the death of all eight gerbils.

According to scientists, the other reason for death among the animals onboard was "the stresses of Space," as reported by Yahoo! News.

Still, however, as Phys.org reports, the completion of the task is largely being portrayed in Russian media as a success and a cutting-edge experiment not yet performed by any other country: previously, the longest period animals such as mice had spent in space was 12 days in 2007.

Fifteen of the mice came from France’s Centre National d’Etudes Spatiales (CNES), an organization cooperating with Russia on a study meant to discover the long-term effects of weightlessness on living organisms.

Scientists from both countries hope the experiment will yield results that, upon analysis, can be applied in order to enable humans to travel through space over extended periods of time safely.

“The moon is a great launch pad, it’s basically a big space object on which a whole load of things could be accommodated,” he told state television, according to AFP. “Not using it would be sinful.”

In particular, Russia recently announced its goal of enabling flights to Mars via the Moon through the construction of a base on the latter, the start of which is set for 2030; in all, President Vladimir Putin said the nation is on track to spend nearly $52 billion dollars on its space sector between 2013 and 2020, 58 percent of which will go toward manned space flight.

The planned increase comes after a series of failed projects by the Russian space agency, including the loss of its Phobos-Grunt probe that was supposed to land on Mars but instead ended up crashing back into Earth in 2012.