NASA is preparing to send rats to the International Space Station (ISS) for a longer duration of up to three months to try understanding the long-term effects of micro-gravity on living organisms.

Usually shuttle missions involving rats only last a week or two, according to NASA. The new mission, however, could range anywhere between 30 to 90 days.

The amount of time the rodents will spend in space depends on the availability of spacecraft to ferry them on the trip, according to Space.com.

"This will allow animals to be studied for longer period of time on space station missions," said Julie Robinson, NASA's chief scientist for the space station.

Of the approximate 35 rats sent to space for studies, few of them have gone for more than two weeks, Robinson added.

The schedule for sending the rats to the ISS and returning them back to Earth has not been decided yet.

 A SpaceX Dragon spacecraft usually just launches supplies to the space station, then returns cargo to Earth with a water splashdown. This could possibly be uncomfortable for the "rat-stronaunts."

Usually mice are sent up into space, as they are smaller and their neurocognitive functioning is similar to that of humans, Robinson said.

Mice also require less food, but bringing the rodents on board is just a one of a number of ways in which the space station is changing for science.

Researchers are also pushing for are more life sciences experiments on station, in order to understand the effects of microgravity on living organisms, according to Space.com.

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