Living in the Universe

What this blog is about…

Living in the Universe is a blog on the topic of astrobiology. The audio version of this blog is a podcast by the same name. Your author and commentator is Chris Impey. I’m a Professor of Astronomy at the University of Arizona. Stories are adapted from news items found across the web. Astrobiology is one of the most exciting disciplines in all of science, trying to ask one of the biggest questions we can ask about the universe: Is there life elsewhere? I’m a cosmologist by training, but I have a strong side interest in astrobiology. I teach the subject, and I’ve written a popular book on astrobiology for Random House, called “The Living Cosmos.” Astrobiology is also fun because it’s highly interdisciplinary. At a conference you might find planetary scientists rubbing shoulders with cosmologists, philosophers, biologists, chemists, paleontologists, and geologists.

Given that we still only know one planet in the universe with life on it, why is the subject of astrobiology worthy of weekly attention? Because the research moves forward rapidly on a number of fronts. There’s the convergence of a lot of lines of evidence to suggest there should be other planets out there with life, and probably many other forms of life in the universe.

First of all the universe is primed for life. Stars create heavy elements in their cores and spit them out into space where they become the grist for making new stars and planets around them. Planets are mostly made of heavy elements, so if stars didn’t forge heavy elements and eject them into space, planets couldn’t exist. Stars are also the source of the carbon that’s the basis for biology. The universe has been making carbon for over twelve billion years, so there’s plenty of carbon out there in space and potentially plenty of biology.

There are also a fantastic number of sites for life. Cosmologists have surveyed the universe for galaxies out to distances of twelve or thirteen billion light years and done a pretty good census of how many stellar systems there are to the limit of the observable universe. In round numbers, there are about a hundred billion galaxies. If we estimate the typical number of stars per galaxy and multiply by a hundred billion, we get a stellar census of ten to the power twenty-one stars. Just consider that number for a moment. One with twenty-one zeros after it. That’s a thousand billion billion stars. Think how unlikely it would be for none of the planets around those hundred billion billion stars to have life, for us to be unique?

Not only is the universe primed for life, but the Earth, the only planet we know with biology, has life everywhere. Research in the past few years has shown that life exists in every nook and cranny of our planet, and not just in the visible places but also in the invisible places. Life can be found deep under the surface or within a rock. It’s found in brutal and inhospitable terrains, high Antarctic plateaus, and arid parched deserts. Life is also found in the deep-sea ocean where the Sun’s light does not even penetrate, where the physical conditions are either extreme cold, or extreme heat near volcanic vents, and there is always the extreme pressure of the ocean floor. If life is found everywhere that suggests that life is robust and could survive similarly inhospitable conditions on planets elsewhere.

We haven’t given up yet on finding life elsewhere in our own solar system. Three billion years ago Mars was warmer and wetter and Venus was cooler and wetter; it’s conceivable that all three were alive back then. Mars will be the subject of a series of exciting mission over the next few years, trying to see if fossilized life is present or even current life in water that’s kept liquid under the surface. Jupiter’s watery moon Europa is another possible location for life, and if we find life in the ethane-methane lakes of Saturn’s Titan, it may be unlike any terrestrial life form.

Lab scientists have taken another interesting step to give us a sense of anticipation that life might exist elsewhere. They’ve shown that the steps towards life that took place on the early Earth can be duplicated in the laboratory, so we’re beginning to learn how simple molecules combined to form proteins, enzymes, and eventually the backbone of life itself, DNA and its cousin RNA. This process probably took as many as several hundred million years on the Earth but it happened four billion years ago, so our direct evidence of this process may always be slender. In the lab molecules naturally build from simple to complex. Nobody has watched molecular ingredients evolve into a cell, but many steps along the way have been sketched in by lab scientists.

Another very exciting aspect of astrobiology is the search for planets and their discovery in increasing numbers in the past decade or so. Fifteen years ago we knew of no planets beyond the solar system. Now we have a count of over two hundred and fifty. The number grows by a dozen or so every year. Most of these are giant planets bigger than Jupiter and very close to their star, so very hot and inhospitable to life, we think. But the detection techniques are improving all the time, and we’re within spitting distance of detecting clones of the Earth.

The final research field that’s making headway, although no success yet, is SETI, the Search for Extraterrestrial Intelligence. Some scientists want to leapfrog over our uncertainty in the nature of biological life or its existence on planets elsewhere and look directly for intelligent, communicating civilizations far beyond the solar system. This search is done using radio waves and, more occasionally, light. If it turns out that civilizations are common, then some have presumably developed the capability for space travel and space communication, and with that huge number of stars available, even if intelligence and technology and civilization are extremely rare, there may be potential pen pals out there. SETI is a quixotic quest. It may fail, and it hasn’t succeeded yet in forty-five years of trying. But new capabilities are giving increasing power to this attempt to search for extraterrestrial intelligence.

Living in the Universe will talk about all these topics and more over the weeks and months to come. It will be a mixture of science, of astrobiology, news stories, and occasional bursts of humor and philosophical ruminations. I look forward to your company as we explore the scientific search for life in the universe. Whether you prefer to listen to the podcast or read the blog, give me five or six minutes of your week. That’s half an hour a month or six hours a year, less than 0.1 percent of your time. Join me as we explore one of the biggest questions in all of science, and try to answer the question of whether or not we live in a biological universe.