|The flyer for my public talk this week at Fiske Planetarium|
Later this evening I'll be giving a public talk at Fiske Planetarium at the University of Colorado Boulder! I'm thoroughly stoked to give this talk. We're going to take a journey to some of the worlds in our solar system and also some worlds far beyond and ask ourselves about the types of life that could come to live in such places using the only examples of life that we have to work with, the life from our own world. During this talk, we will consider some of the craziest creatures on Earth and what they can teach us about the types of alien life that may exist out there.
This talk is part of the Above & Beyond: Cosmic Conversations series, organized by my friend, Morgan Rehnberg (find him at Cosmic Chatter). These are public talks that are focused at creating conversations between speakers and the audience so that we can all share in the storied wonder of science, human history, and our place in the cosmos. The Craziest Creatures on Earth will hopefully inspire those of us in the theater at Fiske Planetarium to engage in lasting conversations about how crazy and beautiful life can be, and about whether or not we're alone in this vast universe. Here's a little overview of what we'll be talking about at Fiske Planetarium this Friday night:
|An artist's impression of what Kepler 22b might look like|
Many of us have dreamed of alien worlds, wondering what planets orbiting other stars may be like. We've created alien life in our science fiction and we've imagined what a visit to an alien biosphere might be like. Over the last couple of decades, we have begun to discover only a fraction of the worlds that must exist in our universe. Yet the only life that we've ever known is life here on our Earth, our home. As our species continues to explore more of our solar system and to discover other planetary systems far away, it begins to feel like we are continually approaching a time when we might have an answer to the age-old question "Are we alone in the universe?" What might alien life be like if it exists? Would it be anything like the life we know here on Earth?
Oddness of the Hummingbird
Life as we know it has been on Earth for at least 3.5 billion years, but probably even much longer. Through that time, life has evolved to dynamically fit and fill nearly every ecosystem available on the the thin habitable shell and lower atmosphere of the planet. Since the diversification of multicellular lifeforms during the Avalon and Cambrian Explosions, over 500 millions years ago, plants, animals, and fungi have developed unique body plans and forms of locomotion to better gain energy, fight, reproduce, and live.
Sometimes an evolutionary adaptation comes along that seems bizarre relative to how we live. Take for instance the hummingbird. Hummingbirds are among the smallest birds on the planet, weighing fractions of a pound. Indeed, the smallest known bird in our modern world is the Bee Hummingbird, which weighs less than a U.S. penny coin. Hummingbirds get their name from the humming or buzzing sound that their wings make when we listen to them flying. The hummingbirds's wings beat on average 50 times per second, but have been recorded as high as 200 times per second. They beat their wings so fast that they can fly up to 34 mph (54 km/h) and they can fly backwards and upside-down. But that's not the craziest thing about hummingbirds.
The strangest thing about hummingbirds is that they have a ridiculously high metabolism. For their little body size, they have a massive caloric intake. Hummingbird's will eat between 3 and 8 calories each day in nectar. 3 to 8 calories sounds small relative to us, that's really only a couple of grapes worth of energy, but if we consider caloric intake vs. bodyweight, then we can see that hummingbirds eat 77 times more than us. This is the equivalent of a human eating about 155,000 calories each day. That's a bizarre caloric intake. It makes the hummingbird a crazy creature in my book.
Denny's Beer Barrel Pub in Clearfield, Pennsylvania makes some gigantic cheeseburgers. One of them, The Belly Buster, weighs just over 20 pounds and holds 25,000 calories worth in energy. If we had the caloric intake of a hummingbird, then we would need to eat 6 of these calorie-loaded burgers and then, on top of that, we would need to wash it down with 6 800-calorie milkshakes. And we would need to do this every single day. That seems bizarre relative to how we understand our place in the world.
When we consider what crazy creatures like the hummingbird can teach us about the possibilities for alien life, we have to keep in mind that not all organisms function the same way and we may one day find that alien life is wholly bizarre to us. Maybe there are worlds out there where most organisms have hummingbird-level metabolisms. Maybe there are worlds where vision or hearing have never evolved. Perhaps our alien neighbors have forms of locomotion, sensory organs, and even body structures that are adapted to environments with only limited similarities to our world. To constrain such speculations about alien life, we can take a look at some of the unique environments in our solar system and consider whether Terran organisms could survive in such places.
A Hunk, a Hunk of Burning Love
Venus is our sister planet. It's very similar to our Earth in size and overall composition and it even has clouds, but, unlike Earth, Venus is a world completely obscured by clouds. The thick, clouded atmosphere surrounds and blankets Venus. That's because Venus has the densest atmosphere of any of the terrestrial planets. However, if we strip away the cloud layer and take a look at the surface of Venus using radar imaging (from spacecraft as well as Earth-based instruments), we see a chaotic terrain on a geologically young surface. The surface of Venus is a marred desertscape of volcanoes and plains with ridges appearing as cracks. From orbital observations as well as from a few spacecraft that landed on the surface, we know that the surface pressure of Venus is 92 times greater than that of Earth at sea level. Not only that, but the surface temperature of Venus is a sweltering 863 degrees Fahrenheit (735 Kelvin)!
Currently, we know of no life that could survive in the high temperature and high pressure environment on the surface of Venus, yet there are organisms on our planet that have adapted to high temperatures. Take for instance the microorganisms living along the margins of Grand Prismatic Spring in Yellowstone National Park, Wyoming, U.S.A.
|Grand Prismatic Spring: a thermophile's oasis|
One of the most intriguing worlds in our solar system is our little neighbor, Mars, the 'Red Planet'. Mars has long held the fascination of scientists and the public. In the late 1800's, the astronomer Percival Lowell announced he had made observations of striations on Mars that he thought were canals built by an intelligent extraterrestrial species. Lowell's speculation led to H.G. Wells' story The War of the Worlds and, in many ways, launched the early era of alien science fiction.
Mars has been our most visited neighbor. We've sent orbiters, landers, and rovers to the Red Planet to learn more about it's geology as well as the possibilities for it to once have had life or to perhaps even currently have life. Mars has a great volcanic mountain, Olympus Mons, which is almost 3 times taller than Mount Everest. Mars bears one of the largest canyons in the solar system, Valles Marineris, which is a distinguishing feature when Mars is viewed from far away. The Martian surface is a cold, dry, and dangerous place for most of life as we know it. The surface has an average temperature of around -80 degrees Fahrenheit and there's only around 200 parts per million water vapor in the atmosphere (the Earth's atmosphere has an average of about 10,000 parts per million water vapor). We've known for some time that the surface of Mars is bombarded by intense radiation, since Mars doesn't have the strong magnetic field or the atmosphere that Earth has to protect us from radiation. However, we've recently learned from the Radiation Assessment Detector (RAD) instrument on the Curiosity Rover that the surface of Mars has even more radiation than we had previously thought. The first astronauts that we send to Mars will most likely have to employ shielding of various types to protect themselves from the radiation.
Although the Martian surface will be a dangerous place for humans, there are some organisms on Earth that could easily survive the radiation on Mars' surface. Take for instance Deinococcus radiodurans. The Guinness Book of World Records title holder for "the world's toughest microbe", D. radiodurans is an extremophile that can withstand environments with limited nutrients and extreme dryness and, most importantly, can withstand extremely high doses of radiation. This microbe can withstand a radiation dose over 1,000 times more than what would be lethal to a human. It can survive in the cooling fluids of nuclear reactors. The microbe's very name stand for "strange little berry that can withstand radiation" while some people like to call it Conan the Bacterium. Indeed, D. radiodurans can even survive in the empty vacuum of space. D. radiodurans would have no problems surviving a trip to Mars and even sitting on the Martian surface.
The extreme radiation resistance of D. radiodurans might even make us wonder about alien life that could survive long-term within the emptiness of space. Perhaps there are biospheres where life has learned to launch itself out into space, like little spores traveling between worlds. Perhaps some alien has even adapted to the space environment and become a fully space-fairing creature. What would such a creature look like? Perhaps it would be something like the Tin Man from Star Trek: The Next Generation or Moya from Farscape or perhaps something utterly strange. Would such a creature be anything remotely similar to life as we know it. Would it need to stay close to stars and planets to maintain itself? Those are the questions that bridge between science and science fiction. But we do have good reason to wonder about how organisms get their energy and how biospheres are built. Much of life as we know it here on Earth is built upon the primary productivity garnered by organisms that utilize the light of the Sun for energy, but not all life on Earth requires sunlight to survive.
My graduate advisor, Alexis Templeton, is the head of a team of researchers centered here at the University of Colorado Boulder and including members from several other institutions which have recently been awarded a grant from the NASA Astrobiology Institute to study what they are calling "Rock-Powered Life". Their work will focus on understanding how biology on Earth has come to utilize chemical reactions between water and rocks for sustenance. Life as we know it does not inherently require sunlight to drive primary production. Rock-powered life may be the base of biospheres on other worlds. Take for instance the Galilean moon Europa.
|Comparison on water on Europa vs. Earth (Kevin Hand)|
Here's a crazy creature that might help us answer that question: the Blobfish. These organisms inhabit deep sea environments off the coasts of Australia, Tasmania, and New Zealand. Living where the pressure is several dozen times greater than at the surface, the Blobfish has developed a unique way to maintain its buoyancy. While many fish use gas bladders to control their position in the water column, the Blobfish has body of gelatinous flesh that is slightly less dense than water, allowing the Blobfish to control its buoyancy in deep sea settings. However, when the Blobfish is removed from its natural setting, the one to which it has adapted so well, and brought to the surface, its body structure changes and it basically slumps into a gelatinous mass. This has earned the Blobfish the vote as "The World's Ugliest Animal".
The Blobfish can survive the extreme pressure of the deep sea, but it's only adapted for that environment. When we consider what alien life may be like, we need to be sure we're considering the types of environments where life might have come to be and where life might be best adapted. For instance, what kind of life, if any, could come to live in the environments of gas giant worlds?
In Carl Sagan's television series Cosmos: A Personal Voyage, he discussed speculations about what types of organisms could come to thrive in the vast atmospheres of worlds like Jupiter:
Floaters and Hunters. What might they look like? Giant balloon organisms? Giant floating whales? In my mind I wonder if maybe such atmosphere-bound life might develop develops defense mechanisms like a blowfish. Maybe the floaters are giant blowfish-like balloons that can change their position in the atmosphere by bringing in or pushing out gas, and maybe they even look something like blowfish, with spikes and other defense mechanisms adorning their bodies to keep them safe from the Hunters.
As Carl Sagan said, we can constrain our thoughts about the possibilities for extraterrestrial life through physics and chemistry, but these are truly speculations. Until we have examples of alien life to work with, the best we can do is work to understand life on Earth and try to use what we know of life to understand which environments alien life may have come to call home. We can look at worlds like Venus, Mars, Europa, and Jupiter and ask these questions. We can also look further, to other worlds around stars far away.
Since the discovery of 51 Pegasi b, the first extrasolar world we've found, our conception of the number of alien worlds that exist in our universe has been radically expanded. As of today, we have found over 1800 exoplanets and that number is always growing! The worlds we've detected around other stars exist in only a small fraction of the space within our galaxy. Considering the number of planets we've found thus far, it has been estimated that every star in our galaxy should have, on average, at least one world. Of course, some may have none and some may have many, but this still leaves a great number of possible worlds and possible environments for the development of extraterrestrial life. What might those aliens look like? Astronomer and artist, David Aguilar of Aspen Skies has been using his artwork to propose some ideas. He creates models of speculative alien life based on his knowledge of life here on Earth and then places those modeled aliens into digitally created worlds. In what ways can we constrain such work, such speculations? Perhaps we can consider something like sensory perception.
Take, for instance, the Greater Wax Moth. This organism has the greatest range of hearing of any known organism on our planet. Not only that, but the Greater Wax Moth has a hearing range that lies outside of the range of sounds that we humans hear. It has alien hearing here on Earth. It's evolved such hearing so that it can hear at frequencies up to 300,000 Hz, allowing it to "out-hear" it's natural predator, the bat. Bats use high-frequency sounds in their echolocation. It allows them to "see" what they hear. The Greater Wax Moth has evolved to hear and to speak above the frequency at which bats echolocate.
An even crazier creature might be the Mantis Shrimp. The Mantis Shrimp has the greatest perception of light and color of any known organism. While we humans only have 3 color receptors in our eyes, Mantis Shrimp have 16! Writing in his webcomic, The Oatmeal, Matthew Inman has said of Mantis Shrimp that their sight is like a "thermonuclear bomb of light and beauty"! Not only do Mantis Shrimp have the greatest vision of any known organism, but they also happen to pack the hardest punch:
The Mantis Shrimp is a crazy creature. It sees in ways that we can't comprehend and it kills using a deadly knockout punch. Might there be alien worlds where the vision of the Mantis Shrimp is only the beginning? Or worlds where the deadly force of the Mantis Shrimp's punch would be considered puny?
What could organisms like the Greater Wax Moth and the Mantis Shrimp teach us about alien life? What about the Hummingbird, extremophiles like Deinococcus radiodurans, or the Blobfish? When there are aliens such as these living amongst us, perhaps it suggests that the possibilities for life in the universe are endless.
I didn't even start to touch on intelligence and consciousness, robots and machine life, or even some of the myriad ways in which microbes might dominate alien biospheres, and yet there are great examples to be found in those realms as well. The bridge between science and science fiction lies not only in imagination, but in considering what may yet come to be.
As Carl Sagan mentioned in that video from Cosmos, there is no predictive theory of biology. Not because it doesn't exist, but because we don't yet have enough to go on to determine if there could be one. Maybe life does follow certain rules and we will one day find that many aliens are very similar to us, or maybe life follows few rules and alien life will appear utterly and wholly alien to us. Considering all of the crazy creatures on Earth can help us to constrain our speculations about alien life, but, until we determine if we are or are not alone in the universe, all we can do is continue to look at our one example of a biosphere and say "what might this mean?"