by Shane L. Larson
More than any other world in the solar system, Mars has captured the imagination of the human race (except maybe for Pluto, but it’s not a planet, right?). Mars has dominated our imaginings of other worlds for more than a century, beginning with H.G. Wells’ masterpiece of invasion, The War of the Worlds. Since The War of the Worlds was first written, many other tales of adventure, danger and horror have been penned or filmed concerning Mars — Kim Stanley Robinson’s epic Mars Trilogy, the classic 1964 film Robinson Crusoe on Mars, Elton John’s sonorous musings that Mars is no place to raise a family in “Rocketman,” and many many more.I was first exposed to Mars in elementary school, through the reading of Ray Bradbury’s The Martian Chronicles, followed closely by viewing the 1979 screen adaptation of those Chronicles starring Rock Hudson. Bradbury’s Mars was a distant frontier, populated by indigenies resisting the influx of pioneers from Earth. Those pioneers were attempting to create a human civilization on Mars, ignorant of the fading race of natives who lived on the red sands before them. Having grown up in the American West, descended from a long line of ranchers who had homesteaded on the front range in Colorado, it was a familiar tale to me cast on a fantastical tapestry of rocket ships and alien landscapes. Bradbury’s tales of Mars are stories humans have always told about the frontier — tales of discovery, of finding out who we are by looking through the lens of our interaction with (and ignorance of) other lifeforms we have discovered. In this case, the other lifeforms are the Martians.
The word “Martians” has come to mean more than just beings of Mars; the name has become synonymous with any alien species, vaguely if not outright humanoid. Tales of Martians are often an allegorical mirror of the best ideals and worst fears we have about our own species. Sometimes Martians are wise and benevolent; some, like the ghosts in The Martian Chronicles are noble and introspective in the face of extinction. Sometimes Martians are implacable and malevolent conquerers bent on owning the Earth, like the invaders in The War of the Worlds.
It was only natural that Mars become a focal point for our musings about other intelligent species. Since the invention of the telescope, Mars has sung a siren song to the human race. It is the only planet whose surface can be seen through a telescope, giving us tantalizing glimpses of icy polar caps, vast dark plains that change with the Martian seasons, and long sinuous markings that look for all the world like river channels. It is easy to tempt our imaginations with the idea that Mars could be much like the Earth.By the 1970s we discovered that Mars was indeed much like the Earth — volcanoes and canyons, ice caps and river valleys. Our landers sent pictures of rocky red deserts, studded with boulders and rolling landscapes that terminate at the foot of mountains on the distant horizon. But Mars is simultaneously unlike its neighbor, the Earth. The volcanoes are the largest known in the solar system; the largest canyon is a rift valley that is large enough to stretch from New York to Los Angeles; craters stud the surface, worn by the ages but not completely disappeared; and there is not an open body of water to be found anywhere on the planet. Perhaps most importantly, we have failed to find any sign of life anywhere on the planet. Unlike our home the Earth, Mars may very well be a dead world, if indeed it was ever alive at all.
Thus, I was electrified on a summer’s day in 1996 when a stunning announcement was made. Tiny, mineralized structures had been found using high resolution images of a Martian meteorite known as ALH84001 (name decode, from right to left: 001 = first meteorite found, 84 = in 1984, ALH = in the Allan Hills region of Antarctica). The structures looked very much like microbes one might encounter on Earth, leading to the very real possibility that the mineralized structures may be fossilized infusoria from the planet Mars.
Like all monumental discoveries in science, the announcement generated tremendous debate. The evidence is not completely unambiguous, and there is still much skepticism about what ALH84001 is telling us. But it opened up the very real possibility that microbial life could have arisen on Mars, suddenly forcing all of our idle speculations and daydreams about Martians into a definite shape and form. The human brain is fickle, particularly with regard to the kinds of daydreams it finds compelling — a Universe where all the life in the Cosmos consists of Earthlings and a few microbes on Mars just isn’t that exciting! Microbes, shmicrobes! So it comes as no surprise to me that I have noticed a subtle uptick in the number of adventure stories told not about Mars, but about other worlds in the solar system: Europa near Jupiter, or Saturn’s enigmatic moons, cloud-swathed Titan and cryovolcanic Enceladus.
Why is that? Why are we, at least sub-conciously, singing blues for the Red Planet? I suspect it is because we have landed on Mars and mapped the planet in exquisite detail from orbit. Mars is by no means a fully explored world; we have roved only over 49 km of Mars, but the planet has a total surface area roughly equal to the land area of Earth. There is no way our 4 little rovers (Sojourner, Spirit, Opportunity, and Curiosity), and a handful of landers have seen every nook and cranny of the vast Martian frontier.
Never-the-less, we have yet to see indications of any large lifeforms. Our cameras have sent back no pictures of Martian tapirs, no pictures of many-legged thoats, no pictures of giant sandworms. The net result: we have given up on the idea of there being substantial lifeforms. We’ve seen enough to convince ourselves that if there is life on Mars, it will be microbial.
Don’t get me wrong — without a doubt, the discovery of a single Martian micro-organism will transform biology forever, but it is not what we’re really looking for! Microbes are not what we long to discover — we long to find companions in the Cosmos. The discovery of a single large organism, whether it is the Martian equivalent of a squirrel, or stag beetle, or snail, would tremendously boost our hopes of one day finding life we can communicate with.
And so, our imaginations have moved on to new unexplored worlds that could still hide the greatest discovery we have ever imagined. Foremost among these, is Jupiter’s icy moon Europa. Europa is sheeted in ice, a solid blanket covering a sub-surface ocean. What lies beneath the ice? With so much water, could it perhaps harbor life? There must be heat sources to keep the sub-surface ocean liquid. Perhaps the constant squeezing by Jupiter’s gravity has produced volcanic thermal vents that provide the heat to keep the ocean liquid. On Earth, deep ocean thermal vents were discovered by explorers in 1977 aboard the Alvin manned submersible. Much to everyone’s surprise, the area around the vent was thriving with life, despite the intense heat and high acidity of the water.The discovery of life around the hydrothermal vents startled us, but scientists soon realized they were seeing an example of extremophiles — lifeforms that have evolved to uniquely survive in an environment that would normally be too extreme for fragile beings such as us to survive in. This epiphany opened our eyes, and we see extremophiles everywhere on Earth. A famous and prominent example are the microbial algae mats around the thermal features in Yellowstone National Park — the colored bands surrounding a feature like the Grand Prismatic Spring are simply different species of algae, each tolerant of different water temperatures. In most extreme environments, the extremophiles are microbes, so even a planet like Mars could harbor life, despite the cold, despite the aridness, and despite the ultraviolet radiation. The discovery of microbial extremophiles has amplified our confidence in the odds that there is life elsewhere in the Cosmos, but it has done little to dampen our enthusiasm for large lifeforms. In reality, microbial extremophiles should boost our chances of finding more complex organisms, if the conditions are right. The deep ocean thermal vents are particularly interesting examples when considering life on Europa, not just because there may be similar vents heating the Europan oceans, but because of the ecosystems we see growing around the vents on Earth. The microbes that thrive in the immediate vicinity of the vents themselves are the base for a very localized ecosystem and food chain. Other, larger, more complex organisms, such as giant tubeworms, also glom onto the thermal vent, feeding farther down the food chain from the microbes who have learned to exploit the extreme environment. If we could sink a cryogenic robot beneath the Europan ice, maybe we could find a similar, complex ecosystem.
We have yet to explore beneath the ice of Europa. But in the minds eye of our fiction writers the adventure is on, and already we are by-passing microbes in favor of speculation about there being big Europans, complex lifeforms against which we can compare ourselves. I was first exposed to adventures on Europa by Arthur C. Clarke’s novel, 2010 (and the associated 1984 film starring Roy Scheider), where the Monolith (already a manifestation of an alien intelligence beyond our own) fosters the growth of big lifeforms on Europa after collapsing Jupiter into a small star. More recently, we have all been charmed by “Europa Report” which follows an expedition to Europa to discover not only microbial life, but something more.
The depiction of the unambiguous discovery of microbial life is very tell-tale of our desperate desire to not be alone in the Cosmos. The first discovery of life beyond the Earth will be a monumental event, but the depiction of discovering extraterrestrial microbes in the movies is similar in excitement to the construction of a new frozen yogurt shop down the street. Discovering alien life should be an Earth shattering event for our culture: we will know for the first time that we are not alone in the Cosmos! But perhaps our fictional heroes, like us, have become immune to wonder at the discovery of microbes. They want to discover something more, something bigger. Microbes, shmicrobes. Why is Europa a destination in stories now? Because Mars, at best, will be the home of microbes, so we are searching for new arenas upon which to cast our dreams, fears, and hopes.But despite our civilization’s fleeting wonder about life on Mars, I still often dream about adventures on the Red Planet and what might be found there. It is still a world full of mysteries, and as worthy of exploration as any corner of the Earth, or any other world in the solar system. What a grand adventure it would be to go hiking across Mars with my daughter, camping near the now dead Spirit rover, to toss rocks over the edge of the Valles Marineris, and take iPhone panoramas of the vast rocky deserts of the Red Planet. I would love to spend an afternoon chipping open rocks on the shoulders of the Tharsis volcanoes, looking for some sign of ancient microbial life as we watch dust devils spin lazily on the plains below.
It may yet be true that Mars harbors no indigenous life, but we’ll never know until we ourselves go, and turn over every rock we can find. It will be the work of a lifetime, indeed of uncountable lifetimes if the exploration of the Earth is any kind of indicator. In the end, there will be Martians, but as Carl Sagan so aptly noted (and Rock Hudson discovered at the end of The Martian Chronicles), the Martians will be us.
This post is part of an ongoing series, celebrating the forthcoming science series, Cosmos: A Spacetime Odyssey by revisiting the themes of Carl Sagan’s classic series, Cosmos: A Personal Voyage. The introductory post of the series, with links to all other posts may be found here: http://wp.me/p19G0g-dE