By Erik Derr (staff@latinospost.com) | First Posted: May 19, 2013 05:10 PM EDT

After spending a month in orbit around the earth, a Russian space capsule carrying a menagerie of small animals has returned home --- with most of its passengers dead.

Roscosmos, Russia's Federal Space Agency, launched 45 mice, eight Mongolian gerbils, 15 geckos, a handful of snails and numerous other species to test how long stretches in a zero-gravity environment affect living creatures.

But, less than half of the cosmic critters survived the flight, Russian news agencies, along with the Global Post, reported.

According to Russian scientists, the animals on board the Bion-M craft either expired from of the stresses of space or because of equipment failure.

Scientists explained before the mission the experiment was intended to test the effects of weightlessness and other factors of space flight on cell structure.

One of the areas researchers will be focused on is how being in outer-space impacted animals' reproductive processes, said a report by Space.com

Russian state television showed the capsule and some of its inhabitants after it landed Sunday in a planted field near Orenburg, about 750 miles southeast of Moscow. The report said not all of the animals survived the flight.

Vladimir Sychov, deputy director of the Institute of Medical and Biological Problems, said it was the first time that animals had spent so much time in space on their own, Fox News reported.

The surviving travelers were to be flown back to Moscow, where a previous report indicated they will be euthanized and then studied.

Nicole Rayl, a project manager for the National Aeronautics and Space Administration, who participated in the mission, said last month that the month in space was "longer than a lot of the other animal and biological missions we've flown. The big importance for us is that we get to compare data from this longer mission with better analytical tools that we have today, [compared] to the missions we've flown in the past that were similar but not exactly the same."

Bion-M1 was Russia's first mission in 17 years dedicated to launching animals into space and the longest flight of its kind in the history of that country's science program.

The last "Bion" mission carried rhesus monkeys, geckos and amphibians into orbit for 15 days in 1996.

If humans plan to travel on long flights to visit other planets, as nearly 80,000 volunteers have applied to do in an upcoming, one-way colonization mission to Mars, it would be nice to know if they will be able to procreate in space, Rayl said.

Some future missions could literally take decades to complete, so sex en route would likely be necessary to continue the human race.

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