Who knew? Space is a zoo.

Last week’s announcement that The Jackson Laboratory in Bar Harbor will soon send a small herd of “mighty mice” to the International Space Station got me thinking: For all the attention we humans get when we journey to the final frontier, what about the other earthly creatures that make the trip?

One of the The Jackson Laboratory’s “mighty mice.” Jennifer L. Torrance/The Jackson Laboratory

Who are they?

What are they?

And how have they fared?

Full disclosure, I love all things space. As a child of the 1950s and 1960s, I thought I knew pretty much all there is to know about our penchant for strapping ourselves to massive rockets and hurtling skyward in the glory of human exploration.

But when it comes to animals, I’m now ashamed to admit, I had no idea.

Monkeys and chimps, dogs and cats, butterflies and fruit flies, take your pick. Since the French brothers Joseph-Michel and Jacques-Etienne Montgolfier first packed a sheep, a duck and a rooster into a hot-air balloon in 1738 to see how they’d do at 1,500 feet (they did just fine), we’ve looked repeatedly to animals to join us in our heavenly pursuits.

Check that. In the early days of space travel, we actually sent them first for one simple reason: We were too chicken.

Fair warning, it wasn’t always pretty.

Take Laika, for example. She was a 3-year-old Russian mutt wandering the streets of Moscow one day in 1957 when Soviet scientists picked her up, strapped her atop a Sputnik rocket and … off she went to become the first animal to orbit the Earth.

Problem was, amid the heat of the Soviets’ space race with the United States, the technology for re-entry into the Earth’s atmosphere had not yet been perfected. Much to the horror of animal rights groups worldwide, Laika never made it home.

Enos the chimp did return – barely. Sent aloft in late 1961 as a dress rehearsal for John Glenn’s first human Earth orbit, Enos was supposed to carry out simple tasks on command – until, that is, the “avoidance conditioning” device to which he was attached broke down and hit him with 76 separate electric shocks as he hurtled through two Earth orbits.

By the time Enos’ space capsule was recovered in the Atlantic Ocean by the USS Stormes, NASA later reported, the irate chimp “had broken through the protective belly panel and had removed or damaged most of the physiological sensors. He had also forcibly removed the urinary catheter while the balloon was still inflated.”

If only chimps could talk …

Who were the first earthlings to fly around the moon?

Not swarthy Apollo astronauts. Rather, they were a Soviet menagerie of two Horsfield tortoises, wine flies and mealworms. All returned safely, albeit a tad underweight.

Bullfrogs had their moment in the sun in 1970. Two were launched on a no-return excursion to NASA’s Orbiting Frog Otolith satellite, where they contributed to research on balance and motion sickness.

Then there are the mummichogs – the first space fish. Found along the Atlantic coast in the United States and Canada, they joined astronauts Alan Bean, Owen Garriott and Jack Lousma aboard Skylab in 1973 to dive deeper into the mystery of space sickness.

At first, the mummichogs had trouble swimming in a straight line, apparently confused about which way was up. Recalled marine ecologist David Samuel Johnson a few years ago in Scientific American, “As the mummichogs looped, the astronauts vomited. As the urge to vomit subsided in the astronauts, so too did the urge to loop in fish.”

For the record, the mummichogs were accompanied by Anita and Arabella, two spiders whose no-sweat mission was to spin a web in a weightless environment. Which they bravely did, sort of, before succumbing to dehydration.

The 1990s saw a boom in out-of-this-world animal travel. The Russians launched brine shrimp and sand desert beetles. China sent up guinea pigs. Japanese journalist Toyohiro Akiyama traveled to the Mir space station with tree frogs in his luggage. And various U.S. space shuttle flights transported crickets, rats, newts, snails, carp, jellyfish, sea urchins and gypsy moth eggs, to name but a few.

Why anyone would want gypsy moths inside a sealed spacecraft remains one of science’s more tantalizing puzzles. The same goes for cockroaches – in 2007, one named Nadezhda (Russian for “hope”) became the first of any species to conceive offspring while in orbit, proving once and for all that cockroaches can multiply pretty much anywhere.

As for mice, the crew from The Jackson Laboratory joins a long legacy of American space rodents dating back to Moe, Sally and Amy – three black mice propelled 650 miles high via an Atlas rocket in October 1960. As Time magazine reported a week later, the trio enjoyed “liberal rations of oxygen, oatmeal, peanuts and gelatin” on their brief sojourn and survived splashdown near Ascension Island in the mid-Atlantic.

Maine’s mighty mice, comparatively speaking, are space studs. According to Sarah Laskowski, the lab’s senior public relations manager, they’ll go to space only after proving they have the right stuff during a boot camp prior to their Dec. 4 launch.

“Any mice that experience difficulty adapting to the new conditions or show signs of distress prior to launch are excluded from the flight cohort,” Laskowski said in an email on Friday.

That seems unlikely. They’re called “mighty mice” because that’s exactly what they are. Bred by Jackson researcher Dr. Se-Jin Lee to lack the muscle growth inhibitor myostatin, these guys typically grow skeletal muscles twice as large as normal mice.

Their mission: to probe microgravity’s effect on bones and muscles during space flight.

Unlike their predecessors from decades past, these mice will travel in style throughout their 40-day voyage under the watchful eye of Maine-born astronaut Jessica Meir.

Laskowski said the mighty mice will live in “a small hut that enables (them) to huddle and sleep together.” As for their diet, she added, they’ll chow down on food bars that, along with water, will be available “in excess so they can eat, drink and sleep as they choose.”

Enos the chimp would wholeheartedly approve.