Suspense is a way of (arrested) Life
The idea that the earliest forms of life arrived on Earth from elsewhere in the universe and then “took off” here, is not mine. It is not even new and some learned “savants” subscribe to it. Hoyle and Wickramasinghe once suggested that this kind of “seeding” still occurs and life on Earth has a cosmic ancestry. Irrespective of whether that’s the case, let’s examine which multicellular organisms, now present on Earth, could perhaps survive space travel.
Candidates come mostly from the phyla of the microscopic rotifers (wheel animalcules) and the equally small tardigrades (bear animalcules), but a few species of tiny, free-living nematodes (roundworms) also qualify. What these animals, apart from their size, have in common is the ability to enter into a cryptobiotic state when environmental conditions deteriorate; when for example the water puddle or the moss they inhabit dry up. During cryptobiosis, all metabolic activity ceases and the body becomes totally dehydrated. Glycerol and a sugar by the name of trehalose appear to be the key chemicals involved in protecting the body tissues against oxidation and cell membrane fusion or breakage during re-hydration. I have myself witnessed in amazement how rotifers and tardigrades in a drop of evaporating water under the microscope turn into tiny “barrels of suspended life”, ready to resume life when more agreeable conditions return.
Smaller and lighter than when active, animals in the cryptobiotic state can easily be dispersed by wind, which explains why many species of rotifers, tardigrades and nematodes are cosmopolitan. But space travel? During cryptobiosis these animals -and the cutest are undoubtedly the tardigrades with their 4 pairs of stubby and clawed legs, their minuscule black eyes and a round little mouth for sucking up plant juices- are totally anaerobic, i.e. need no oxygen. Some were held in a vacuum at temperatures near absolute zero (-273°C) and reproduced quite normally when revived. Others were put for months into 100% ethyl alcohol during the cryptobiotic state and survived this treatment unharmed. It has been estimated that individual tardigrades may live for 12 to 18 months, but that repeated suspension of life in the form of cryptobiosis increases their total lifespan to 50 years or more. Although that would be ample enough time to reach Mars and beyond -if only someone would accelerate the little critters enough to escape from Earth’s gravitational field- to reach the nearest Earth-like worlds, however, they wouldn’t need 50 years of travel, but thousands of years and all in a state of cryptobiosis. That, for all we know at present, is totally out of the question.
But science is full of surprises like the recent discovery by Hariyama and team in Japan that some organisms as highly evolved as insects under the influence of electron bombardment can surround themselves with a “nano-suit” that’s tough and tight enough to protect them against high vacuum. Although nobody is suggesting that this could mean they could survive space travel, to find high vacuum tolerance in insects is certainly unexpected (and one key requirement of space travel for any organism). Who knows, in the end Hoyle and Wickramasinghe may be right, but it would then simply shift the origin of life to another place in the universe and the mystery how it started there would remain the same. Maybe seeded from somewhere else in space? Another cosmic origin? Panspermia indeed !
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2018.
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