NASA is sending 20 mice on a trip to the ISS

Currently, there are six astronauts aboard the International Space Station (ISS) – well, six human astronauts, anyway. On 2 July, the humans will be outnumbered by some 20 mice taking part of an experiment to see how they cope with an extended spell outside of Earth’s atmosphere.

“Taking part” suggests a certain degree of consent which isn’t something the mice have been able to provide. Unlike the astronaut twins Scott and Mark Kelly – which is (appropriately enough) a twin of this study – the mice have little say on their upcoming adventure, which feels a bit like a space-based mousey version of Big Brother. Which is to say they’ll spend the next period of their life being pricked, weighed and filmed sleeping. In a (merciful) additional break from reality TV, they’ll also have regular stool samples collected.

“It’s hard to imagine how you can get excited about faecal samples,” Martha Vitaterna, a researcher from Northwestern University joked during a teleconference earlier this month. “But believe me, we are really excited about faecal samples.”

Why? Because the aim of the study is to establish how living in space for extended periods can impact Earth-bound creatures’ microbiome. Microbes are responsible for making essential molecules that we – humans and mice alike – can’t produce on our own, and Vitaterna and her team are keen to see if these changes have a measurable knock-on effect to sleep loss, which can disrupt both the metabolism and the immune system.

Two different strains of mice are on their way into space, with one set of heavy sleepers and another group of light sleepers. Ten of the mice will be staying up for a record-breaking 90 days, which may not sound like that long in human terms, but would be the equivalent of nine years for you or me.

Back on Earth, a group of control mice will be kept inside identical habitats to their space-fairing peers. The environments – gravity aside – will be identical with gas composition, temperature and lighting closely maintained with help from a data stream from the ISS.

It all feels quite similar to the Kelly twin study, where the bacterial balance shifted for Scott Kelly when he was in space, but returned to similar levels as his twin brother Mark once safely back on terra firma. Where the experiment will dramatically differ is after the spell on the ISS is over: the mice will be dissected to examine the impact on their internal organs to better understand possible links between inflammation, metabolic shifts and changes to the microbiome.

It’s an undeniably brutal end, but if we’re serious about sending humans to Mars, this is the kind of inside knowledge we really need well in advance of take off.