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The internet loves animals, and loves animals in surprising places even more. So, when a photo emerged showing a frog flying alongside Nasa's Minotaur V rocket as it lifted off from its launchpad in Virginia earlier this month carrying the LADEE spacecraft towards the moon, it was an immediate hit. It has since gone viral.
It may have been, as Megan Garber put it at The Atlantic, "one small step for a frog" and "one giant leap for frogkind", but this acrobatic amphibian was actually not the first to cross paths with space-faring institutions such as Nasa. There is a long history of high-flying frogs.
The first attempt to send a frog into space was on 19 September 1959. Two frogs and a dozen mice were meant to travel towards the stars on a Jupiter AM-23 rocket, but the rocket was destroyed during launch, meaning that the animal astronauts would not go to space that day (or indeed any other day).
Less than two years later, the first frog to actually wind up in space was aboard the USSR's Vostok 3A rocket in March 1961, along with mice, guinea pigs, and cosmonaut Andrian Nikolayev. The frogs were witness to history when Nikolayev communicated over radio with cosmonaut Pavel Popovich in the Vostok 4 rocket, which launched just a day after Nikolayev. It was the first radio communication between two spacecraft.
Froggy spaceflight really came into its own almost a decade later when, in 1970, Nasa launched the Orbiting Frog Otolith spacecraft. "Otolith" refers to the frog's inner-ear balance mechanism, which was appropriate because the mission was designed to investigate the effects of spaceflight and weightlessness on motion sickness. The otolith is a critical part of the vestibular system – the part of our nervous systems that help us maintain balance – and it works mainly by detecting acceleration due to gravity.
Frogs were used because their inner ears turn out to be quite a useful model for the human inner ear, and the factors that induce motion sickness in frogs are the same as those for humans and other mammals. In addition to their use as model species, frogs were also logistically valuable thanks to their amphibious nature: preflight surgery could be performed out of water, but the frogs could then be kept in water during the experiment. This was important for two reasons: first, the water cushioned the critters from the vibration that comes when you launch an 18,000kg Scout rocket into space. Second, the water would cycle carbon dioxide and heat away from the frogs, keeping them cool. This was all possible because frogs can breathe through their skin while submerged in the comfortable 60F water.
Here's how it worked: Two bullfrogs (Rana catesbeiana) were selected to go to space. They both had electrodes implanted into their thoracic cavities (the space that holds the heart, lungs, and other internal organs) and in the neurons that form the vestibular system within the ear. The electrodes would provide the data that scientists needed to understand how the animals experienced space motion sickness. Then, the nerves that connected to their limb muscles were cut, to prevent them from splashing around and accidentally removing the electrodes.
The results of the electrocardiogram recordings indicated that the frogs remained in good health throughout the flight. By the final day of the six day flight, the frogs' vestibular systems had essentially returned to normal, suggesting that they acclimated to the unfamiliar situation in which they found themselves.
Frogs made another trip to space in December 1990, when Toyohiro Akiyama, a Japanese journalist, brought Japanese tree frogs (Hyla japonica) with him to the Mir space station. While on board Mir, the frogs participated in more experiments regarding weightlessness and motion sickness, as well as locomotion and their responses to external stimulation. One of the things that Mir researchers discovered was that the frogs' ability to change their body colour to mimic the colour of the surface they were sitting on was delayed or absent due to the microgravity environment. Their responses to other sorts of stimuli were generally intact as long as they maintained stable contact with a surface. Once the frogs lost contact and began floating in the zero-G space station, they lost their ability to co-ordinate their movements and to orient themselves properly.
Frogs were occasionally brought aboard Nasa shuttle missions through the rest of the 1990s along with a menagerie of other critters: crickets, mice, rats, newts, fruit flies, snails, carp, fish, sea urchins, brine shrimp, jellyfish, various insects, and quail eggs.
Since then, frogs' exposure to space-like environments has come mainly aboard aircraft executing parabolic flights: vomit comets. Researchers have continued to use frogs and other amphibians as models for understanding the effects of weightlessness on the body and for understanding emesis, the vomit response.
So, the high-altitude frog that made the headlines last week was just the latest in a long line of amphibians to become involved in mankind's ongoing effort to reach the stars. Though it may have indeed been the first frog to take a Nasa-sponsored flight by accident.
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