It is a question that has been asked through the centuries – Are We Alone? Is there intelligent life on other planets or in other galaxies in the universe?
With today’s technology, astronomers, around the world, are closer to answering that question.
For 2014 Jansky Lectureship recipient Dr. Jill Tarter, the pursuit of an answer has been a lifelong journey through the universe. Tarter gave her lecture “Are We Alone? Searching for Intelligent Life Beyond Earth” at the National Radio Astronomy Observatory in Green Bank last week.
Tarter is the Bernard M. Oliver Chair for SETI (Search for Extraterrestrial Intelligence) at the SETI Institute in California where astronomers pursue evidence of intelligent life, following in the footsteps of astronomer Karl Jansky.
“In the second half of the twentieth century, thanks really to the pioneering work of Karl Jansky, a whole bunch of new tools for observing the universe were built,” Tarter said. “After World War II, we had these radar systems that were developed during the war, and we turned them around to look at the universe. The entire field of radio astronomy was born, and I had the privilege to spend a scientific career helping to build on those tools to try and answer a really old human question about whether we are alone in the universe.”
One of Tarter’s goals as a scientist is to show people where they stand in the vast universe.
“I think this cosmic perspective that I’m going to try to share with you is extraordinarily important,” Tarter said. “In fact, it is one of the most important things to help us as a species, as a technological civilization to survive into a long future. The story of all humans began billions of years ago because, in truth, it takes a cosmos to make a human, and we are intimately connected with those long ago and far away events.
“Humans can trace their lineage – not just back over the centuries of our families, not just back through the millennia of human civilization with its arts and its architecture, and its various experiments in governance, not just back across the millions of years since humans branched off from the giant apes, not just back to the 2.4 billion years during which our atmosphere has been perfused with oxygen, thanks to the photosynthetic labors of blue-green algae, and not just back to about five billion years ago when the sun and the solar system and our planet were formed, but we actually trace our lineage all the way back about eight billion years to the explosion and death of a massive star which ended its life in this catastrophic explosion that spewed into the interstellar medium,” she continued. “It’s taken us millennia to piece together this story of where we came from, and today we’re continuing on this journey to find answers to questions about who we are and why we are and what else is there in the universe and, of course, is anybody else out there.”
Several spacecraft sent into space have sent information back to Earth confirming that while there currently is not life on other planets, there is a possibility other planets and moons have the ability to support life.
The Curiosity Rover sent back pictures of a desolate, cold Mars. Although the pictures didn’t show any signs of life, it gave an up close and personal look at the possibilities.
“Curiosity wasn’t designed to look for life on Mars,” Tarter said. “Curiosity was designed to tell us whether the conditions for life might have once existed on this neighbor planet. Today, the surface is a cold, frozen desert, but thanks to Curiosity, the rovers before it and Earth-based telescopes, we know that Mars, our sister planet, was once much wetter and warmer – and for a significant amount of time. We don’t know in detail what happened to all the water on Mars. There may be pools of water beneath the surface where if life ever started on Mars, it might still exist today, or we might find some fossil evidence of life on early Mars.”
The solar system also has several moons that show signs that they could support life, including Jupiter’s Ganamede, Callisto and Europa, and Saturn’s Titan and Enceladus.
“Ganamede, Callisto and Europa are covered in ice,” Tarter said. “We think beneath that ice, there are salty liquid water oceans. Europa is about the same size as the Earth’s moon and we think under its icy shell, there might be twice as much water as in all the Earth’s oceans and that water’s been there for four-and-a-half billion years.
“Saturn has a tiny little moon Enceladus,” she continued. “Nobody thought much about this moon. I mean, who could care about such a little moon, right? But we have a spacecraft that’s investigating Saturn right now. It’s called Cassini and that spacecraft shows us some amazing things about that little moon. When we look at its south pole, we see these incredible eruptions – what we call cryovolcanoes. Somehow from the cracks in Encealdus’ surface, there’s this outgassing of ice and organic material from apparently a liquid ocean under its outer surface. This is a very exciting prospect for individuals who want to explore the solar system, to understand it better from a planetary geology point of view, but also to look and see if perhaps in our solar system, we can find a second Genesis – a second independent evolution of life.”
Exploring the area around the solar system – galaxies and stars – has also brought to light information about uncharted planets that have a similar size and make-up as the Earth.
“In 2009, we launched this spacecraft called Kepler, and Kepler’s job was to go looking for those small planets like the Earth,” Tarter said. “It stares at 170,000 stars that are in this one patch of sky, just a little bit above the Milky Way. It is constantly waiting for one of those stars to blink – when a planet passes in front of the star, causing a shadow on the star and its light to dim just a little bit – it blinks. It turns out, a whole lot of those stars are blinking.”
Currently, the Kepler website states the spacecraft has discovered 4,234 planets orbiting stars and, of those, 989 have been confirmed by observations from the ground.
“There are a lot of planets out there and when we do the statistics of the whole sky, we realize that almost every star in the sky will have planets,” Tarter said. “Some of those planets are particularly interesting to people who are thinking about life beyond Earth because some of those planets are at just the right distance from their star so they’re not too close and hot, and not too far away and cold.”
The information collected by Kepler has been studied and planets similar to the Earth in size and distance from their star have been categorized specifically for observation.
With the countless possibilities of life-supporting systems in the universe still out there, the SETI Institute and scientists like Tarter continue to search for the answer to the question: Are We Alone?
“We’re the living, breathing products of ten billion years of stardust,” Tarter said. “All of us are what happens when the primordial hydrogen and helium from the first earliest moments of the expanding universe evolved for so long that it began to ask where it came from. In that context, the largest here and now, it seems to me to make ever more sense to ask and try and find the answers to this question – is it really just us? Are we alone in this colossal sea of matter and energy and chemistry and physics? Well, with homage to a pretty good science fiction movie, ‘If it’s just us, it seems like an awful waste of space.’”
The quote comes from Carl Sagan and his book “Contact,” which was made into a Hollywood film of the same name in 1997, starring Jodie Foster. Foster’s character was partially based on the life and career of Tarter.
While they are searching for intelligent life, Tarter explained that the goals of the SETI Institute is to actually find signals that might have been sent by extraterrestrials.
“What SETI does is to apply the tools of the astronomers to see if we can sense the technologies used by an older distant civilization,” Tarter said. We do things that broadcast our presence with sufficiently powerful systems that might be detectable over interstellar distances. In fact, we can’t detect intelligence directly. What we do is we use technology as a proxy. We’re trying to detect evidence of somebody else’s technology.
“Whether or not SETI will succeed depends on two things, one – are there any other technologies out there, and two – how long do they last.
“Because we are a really young technology. We’ve been doing these sort of experiments with electromagnetic radiation for about a hundred years, so we’re a young technology in a ten billion-year-old galaxy. We don’t know whether it’s possible to become an old technology – old in cosmic time.”
In the past 50 years, while the search for intelligent life has grown by leaps and bounds, SETI is far from finished exploring the universe.
“Say that I need to search [an area] equal to the volume of the Earth’s oceans and you ask how much searching have we done in fifty years,” Tarter said. “Well, it turns out it’s about an eight ounce glass of water. So we’re asking a big question and this is what we’ve done in searching. If your question was ‘are there any fish in this ocean?’ and you dipped a glass in the ocean and you looked at it – ‘well, no fish in there.’ It’s an experiment that could have worked but the fact that it didn’t work is not likely to make you conclude there are no fish in the ocean. It’s just that you haven’t searched hard enough. That’s where we are.”
To explore the night sky and search for life, the SETI Institute uses the Allen Telescope Array, an array of 42 radio telescopes working in unison to collect data.
“We’re in the process of changing out all of the receivers on our forty-two telescopes,” Tarter said. “We’re looking for signals that we don’t think mother nature can make. We’re looking for signals that we think are obviously engineered. We’re looking for these artifacts.”
While, at this time, she is unable to answer the question – Are We Alone? – Tarter is not giving up hope that the SETI Institute and the Allen Telescope Array will find proof of intelligent life in the solar system or neighboring galaxies.
For more information on the SETI Institute, visit www.seti.org