We live in an awesome universe, rich in remarkable, complex, phenomena. Every advance in our observing capabilities reveals new and often unpredicted objects, such as other planetary systems, and processes in the universe. Of all these phenomena, the most marvelous, and at the same time of the greatest interest to us as human beings, is life in the universe. How many planets exist which might support life? Indeed, what is required for life to exist? How does life start? How does it evolve, and what fabulous creatures can evolution produce? How often do intelligent creatures appear in the giant tapestry of life? It is exactly these questions, and all of them, which are being addressed by the scientists of the Center for the Study of Life in the Universe, LITU.
To make progress towards answers, some scientists in the Center are searching for other planetary systems by relentlessly watching for the slight dimming of starlight which occurs if a planet crosses in front of the star as seen from Earth. We even utilize an automated telescope for this program in the very harsh winter of Antarctica, where almost six months of continual darkness provides ideal observing conditions. In the near future our scientists will participate in the Kepler spacecraft mission, which utilizes a special telescope that will look for the characteristic dimming caused by planetary eclipses. For the first time, there will be adequate sensitivity to detect planets like the Earth. This telescope will continually watch a hundred thousand of stars, always alert for the tiny changes in brightness which would signal the presence of other Earths.
Our scientists are working to understand how planets change over billions of years, and especially how their atmospheres change in their chemistry, temperature, and pressure with time. Especially - will atmospheres suitable for life be common and enduring?
And where conditions are right, will there be life? LITU scientists have been leading innovators in suggesting new scenarios, which might have led to the origin of life on Earth and elsewhere. Did it happen in Darwin's "warm little pond", or at the steaming undersea cauldrons of the ocean, spewing forth hot water, rich in suitable chemicals? Or did it, perhaps, develop in an exotic place, such as within the rocks of the Earth, a new suggestion made by one of our scientists.
Not long ago we believed that only Sun-like stars would provide the right conditions for life on their planets. Around these bright stars, planets can orbit at a distance where temperatures are comfortable. But little did we know: great surprises were in store. The enormous power of the greenhouse effect to warm planets far from their stars was not recognized until we discovered that the effect was so important on Venus that the planet's surface is hot enough to melt lead. We see a sort of greenhouse, actually made by a many-mile layer of ice, on the satellite Europa of Jupiter, so far from the Sun that the brightness of sunlight is only a few percent of that on Earth. But there is liquid water there, and a lot of it - much more than in all the oceans of Earth combined. Could there be life in this giant ocean? Our scientists are exploring this possibility, both in theory and in the planning of missions to Europa to search for signs of life.
The planets of dim red dwarf stars, also called M stars, are a new and exciting possibility. Long neglected as targets for SETI searches, they comprise eighty percent of the stars in our galaxy. Yet their starlight is so faint that only planets in close orbits would be warmed. But what warming this would be! In orbits so small, planets would be tidally locked, with the same side continually facing the star, like the near side of our Moon always faces Earth. The center of the sunny side of the planet could be scorching. The dark side would be a frozen wasteland. But, somewhere between these extreme environments, conditions might be just right for life. Perhaps on these planets there is a "Camelot" zone, just right for life, which makes planets like ours seem like the slums of the Galaxy in comparison. What might life be like in a place where the weather hardly changes, and the "sun" never sets?
Perhaps most provocative of all are a class of planets which must exist, but which we have never seen. These are the planets which have been ejected from their systems during the turmoil which accompanies the birth of a planetary system. These "rogues" are destined to wander through space alone, cosmic nomads, with only the light of distant stars falling on them. Shouldn't life be impossible there? Maybe not. Just as the outer giant planets of our system are warm in their interiors due to radioactive decay and other sources of energy, so the rogues could well have a deep enough atmosphere, and greenhouse effect, that they can provide a long-lived habitat for life. How strange that life must be, if it exists!
Once life begins, it is opportunistic, and will proliferate in habitats we can barely imagine. Even here on Earth, we find life surviving near nuclear reactors, bathed by radiation we once thought no life could bear. Life survives--and even thrives--in such extreme environments as the acid hot springs of Yellowstone National Park, the depths of the polar oceans, the desiccated valleys of Antarctica, and the high altitude lakes of Licancabur volcano on the border of Chile and Bolivia. We know this at the Institute because our scientists have been to the summit of Licancabur, even in the summit lake, and will be again. SETI Institute scientists study "extremophiles", the life existing in extreme environments, to explore the possible limits of life on other worlds.
As we search for signs of life on Mars, we will continue to follow the water. But what else is required for life? How was the earliest oxygen--so essential to large-brained creatures like ourselves--generated on terrestrial planets? Might early Mars have harbored enough nitrogen to foster life? In the laboratory, we can recreate exotic environments, otherwise far removed from us in time or space. In Chile's parched Atacama Desert, and other locations around the Earth, we find analogues to early Mars. Our scientists are addressing these questions. Using new instrumentation, we will burrow below the surface of Mars. We also monitored the hazy atmosphere of Titan during the descent of the Huygens probe.
Given primitive life in many places, what then? SETI Institute scientists are exploring the developments that led to the existence of intelligent creatures on Earth, in hopes of determining how often high intelligence should appear, and perhaps technology as well. Are these rare, and we are almost freaks, or, given enough time, is intelligence and high technology inevitable on planets even somewhat like the Earth? The answers to these questions are some of the most important, yet least known in all of astrobiology. SETI Institute scientists are among the most active in trying to find the truth. The answers are of profound importance to science, but also in a practical way, since they give us guidance in planning our SETI searches.
In our Life in the Universe Center, the Institute is conducting perhaps the broadest program of any institution addressing the origins and nature of life in the universe. In so doing, we hope to contribute to the understanding of some of the oldest and most profound questions of science and philosophy.