Travelling to the stars is still a distant dream for humankind. Awe-inspiring though the idea may be, we simply don’t live long enough to cross the immense distances involved before dying. But a humble wood frog might hold the key to going to sleep on Earth and waking up on another planet.
Problems with human longevity aside, building a spaceship to travel through interstellar space is a feasible prospect. In fact, human technology may have already left the solar system, or be on the verge of leaving, in the form of the space probe Voyager 1.
Launched in 1977, Voyager 1 completed its mission to observe other planets in 1980 and has been moving steadily through the outer realms of the solar system since, sending back information on conditions. Now scientists believe it may have left the area of our sun’s influence and reached an ‘magnetic highway’ that precedes its arrival in interstellar space.
Voyager 1 is powered by the slow decay of radioactive plutonium. It will start running out of energy for its instruments in 2020, and finally lose all power in 2025. Then it will simply drift, the first human artifact in interstellar space, lost forever. It will probably never encounter another star system
But Voyager 1’s remarkable story shows that even 36 years ago we had the technology to travel beyond our solar system. Currently, a non-powered technology such as solar sails could theoretically take us much further, wherever we wanted to go. The major problem isn’t finding a means to get to other worlds, it’s the time it would take. Assuming we could build a self-contained, self-sustaining spaceship that would support life indefinitely, and that we could solve problems caused by a zero gravity environment, it would still take several human lifetimes to reach another planet.
Finding candidates who were willing to be the great-grandparents of planetary colonists would undoubtedly be possible. Judging by the massive response to an invitation to be the first people on Mars, which saw 78,000 applicants, no doubt there’s a smaller but still sizeable number who would also be happy to commit their unborn children to living and dying confined to a spaceship.
The risks of such a journey are so great, however – given the human potential for self-destruction and the amount of unknown variables the travellers would have to deal with, physical and psychological – that it would be safer to put the colonists in some form of suspended animation for the duration. We already know how to do this, to an extent. During complex heart operations, surgeons are now cooling patients down and stopping their hearts in a technique called Deep Hypothermic Circulatory Arrest. When body organs are cold they require much less oxygen and the body enters something similar to a state of hibernation. But to suspend bodily functions for hundreds of years with no long term effects would require extreme measures. Cooling wouldn’t be enough. But freezing might be.
The wood frog Rana sylvatica is no stranger to cold. As a normal part of its annual hibernation up to two thirds of its body freezes solid for weeks at a time. When temperatures rise to above 0 degrees Celsius it simply thaws out and continues its daily routine, apparently unaffected. Zoologists studying this remarkable phenomenon found that the frogs store huge amounts of glycogen in their livers in preparation for winter, and prior to freezing they convert it to glucose, which floods their cells. Glucose works like antifreeze, preventing ice crystals forming in cells. The team also found a mysterious third substance that seems to be vital to the process.
Might it be possible for humans to enter a similar state of suspended animation? Human brains are much more complex than frogs’, and it would be impossible to test suspended animation technology for anything like the length of time needed to ascertain its safety for interstellar travel. One thing’s for sure, though, there are going to people who are willing to give it a try.