The other day I was listening to a CBC Summer Edition discussion about space exploration, and specifically putting human beings on Mars. The discussion centred on the risk of contaminating Mars with organisms from earth, but also the risk of introducing martian organisms to earth. There was also some discussion of the “Are we alone” question.
Based on fairly recent estimates, there are perhaps 300 billion stars in our galaxy alone, and there are around 100 billion galaxies! These are numbers that we can’t even fathom (at least I can’t). The likelihood that planet earth is the only planet that supports some kind of lifeform is clearly highly unlikely. That doesn’t necessarily mean that there are little green men flying around out there, but it does mean that there must be other forms of life. Life as we know it on earth is highly adaptable. If there is a source of energy, it is likely that some kind of organism is able to take advantage of it. On our own planet, the most simple form of life, i.e., very “primitive” organisms first emerged relatively soon after the formation of earth, perhaps as early as 3.5 billion years ago, i.e., about 3 billion years before we have good fossil evidence of the emergence of “higher life” forms during the so-called Cambrian Explosion, and only 1 billion years after earth came into existence! The first life forms were quite different from what we have today, perhaps similar to bacteria using sulfur as energy near ocean hot vents. Likewise, any life forms surviving on Mars, or existing on other planets could be completely different from life on earth. Either way, IF such life forms were introduced to earth, the consequences could be anything from no impact at all, because they earth would be unable to sustain life of them, to complete annihilation to existing life forms on earth, because our organisms have no defense against these invaders.
My thinking is based on the behavior of organisms introduced into novel environments on earth, e.g., from Europe to North America or Australia. Examples abound, e.g., rabbits, cane toads and prickly pear cactus in Australia, and gypsy moth, emerald ash borer, white-nose syndrome in bats, and chestnut blight in North America. If we think of earth as an island in our galaxy, then it may be easier to understand what space travel could mean once it ramps up in frequency. Hawaii was fairly protected before European contact, but with increasing travel and trade alien organisms were introduced on purpose as well as accidentally. Today a large number of animals have gone extinct there due to the introduction of invasive species (See my three blogs on Hawaii here, here and here for more specifics.) On earth, because organisms have evolved on the same basic “platform”, organisms have the ability to adapt, but there is no guarantee that space aliens would be similar. Space travel could potentially serve as a bridge between the space “islands” and hence, the potential risks may be substantial.
The above may be dismissed as fear mongering, of course. From a purely personal point of view, I do have another reason for questioning the wisdom of extensive space travel. I acknowledge that many inventions that we now take for granted owe their existence to space research. Also, as we exhaust resources on our little planet, we may need to figure out ways of accessing resources like minerals from space. However, those goals are very different in my mind from creating human settlements on other planets. The cost of doing so is astronomical (no pun intended). Meanwhile, we know very little about our own planet. The oceans are largely unexplored, and relatively few resources are allocated to change that. In terms of life on earth, we know very little about what lives here. We have described somewhere between 1 and 30% of the species on earth. Even fairly large organisms are discovered on a regular basis by expeditions to poorly explored areas, and sometimes even in well explored areas. It is thought that there are at least as many parasitic species as non-parasites. For example, there may be as many as many as 300,000 parasite species in 45,000 vertebrate hosts (Dobson et al. 2008). Most people would perhaps just as soon get rid of all those nasties, but the fact is that they are part of the ecological food web, and they have important roles to play, whether we like it or not. If we know that little about vertebrates, it doesn’t take a rocket scientist (again, no pun intended) to realize that the invertebrate picture may be much more striking, given that they have had a much longer time to evolve.
In my opinion, we need to start looking after the planet we evolved on. While not unique in terms of harbouring life, perhaps, it is uniquely suited to us (unfortunately as evidenced by our success in occupying way more of it than we are entitled to). More resources need to be made available for science to understand where we live. It is at the peril of the human species that we ignore the warning signs that are now all around us.