Despite centuries of scientific discovery and ever-evolving technology, some of our ancestors' earliest questions remain unanswered. Is Earth the only planet in the universe upon which life exists? If so, where did we come from and why are we here?
While no one knows the answers to these age-old questions, a group of scientists hope a $6.5 million grant from NASA awarded to the Wisconsin Astrobiology Research Consortium (WARC) this summer will bring them closer to the detection of extraterrestrial life. Located on UW-Madison's campus, WARC ties together astrobiologists from UW-Madison, the Jet Propulsion Laboratory and the University of Georgia.
Astrobiology is an interdisciplinary science in search of the origin of life on Earth and whether or not life exists on other planets,"" said Clark Johnson, UW-Madison professor of geology and geophysics, and leader of the WARC group. According to Johnson, astrobiologists use clues from the early Earth to help predict where extraterrestrials live and how to find the trail of cookie crumbs they might have left behind.
""Earth is the only example of life that we've got,"" said Max Coleman, director of the Center for Life Detection at the Jet Propulsion Laboratory, and co-investigator for WARC. ""This being the case, we have to use what we know about life on Earth to our advantage.""
Scientists believe that relatively early on in Earth's 4.5 billion year history, the first signs of life appeared in the form of simple bacteria. Geological evidence suggests that bacteria singularly ruled the Earth for between two and three billion years before the emergence of other forms of life.
""If we ask ourselves, 'What life has been present on Earth for the longest time?' The answer is bugs,"" Coleman said. ""If we want to find extraterrestrial life, our best chance is to start by looking for signs of bacteria on other planets.""
Scientists are now working to develop equipment sensitive enough to identify extraterrestrial bacteria to be used in future NASA missions.
Researchers in Johnson's lab study how bacteria produce irreversible changes to minerals on Earth and how these mineralogical changes, or ""biosignatures,"" can be used as clues for the detection of life on other planets.
""A biosignature is the biological fingerprint of life,"" Johnson said. A biosignature not only signals the presence of life to researchers, but it also provides clues about the type of life it was. Johnson said common biosignatures include footprints and fossils.
""'Biosignatures' must be developed if we are to correctly interpret samples collected on Mars or elsewhere,"" said William Barker, UW-Madison associate dean of the College of Letters and Sciences.
To develop biosignatures of bacteria, researchers are studying how bacteria and minerals interact under atmospheric conditions similar to the conditions of the early Earth. Once the scientists identify biosignatures left behind by bacteria, they hope to develop equipment capable of finding the presence of similar biosignatures in ancient rocks on Earth and to develop instruments capable of identifying biosignatures of bacteria in space.
Ultimately, the WARC team plans to use their findings on Earth to guide their search for life on Mars, a planet that scientists suspect may have once shared multiple characteristics with the early Earth. Although Coleman said NASA has ongoing Martian missions planned for the next decade, there is great need to develop new instruments that can measure biosignatures of bacteria at a fraction of their current size without losing precision and sensitivity - a process that will likely take time and patience.
For the scientists that are part of WARC, the wait is well worth the possibility of discovery.
""I'd love there to be life on another planet, but the evidence has to be airtight,"" Johnson said.
""There's no proof that we'll find what we're looking for in space, but you can't be afraid of failure. At the very least, our studies will help us to gain a better understanding of Earth.""
""There may be life outside our planet,"" Coleman said. ""If there is, the question becomes, did we evolve from it or them from us? My colleague, Joe Kirschvink, from Caltech, likes to say, 'One day we may discover we're all Martians.'""
