What are the limits of organic life in planetary systems? It’s a heady question that, if answered, may reveal just how crowded the cosmos could be with alien biology.
A study arm of the National Academy of Sciences, the National Research Council (NRC), has pulled together a task group of specialists to tackle the issue of alternative life forms -- a.k.a. "weird life".
To get things rolling, a workshop on the prospects for finding life on other worlds is being held here May 10-11. The meeting is a joint activity of the NRC’s Space Studies Board's Task Group on the Limits of Organic Life in Planetary Systems and the Committee on the Origin and Evolution of Life.
Sessions on Earth biology, possible Mars habitats, looking for life on Europa -- a moon of Jupiter -- as well as on Titan, a natural satellite of Saturn, are featured topics on the wide-ranging meeting agenda.
The newly formed study group has some big issues to get their arms around.
Possible alternative chemistries for life are to be evaluated, with an eye toward the prospect that non-standard chemistry may support life in known solar system and conceivable extra-solar environments.
Additionally, the task group is to define broad areas that might guide NASA, the National Science Foundation, and other relevant agencies and organizations to fund efforts to expand scientific knowledge in this area.
Overall, the programmatic goal of the study is singling out research avenues that will appraise the likelihood of "non-terran" life and the potential cost needed to find it. From this will come a recommendation "whether the likelihood of finding non-terran life is sufficiently low that NASA should ignore its possibility, or sufficiently high that it should pursue it," according to a study document.
"This is the first NRC project I have been involved with where scientists have actively been volunteering to serve on the committee. We usually have to corner candidates and then start twisting arms," said David Smith, Study Director for the NRC’s Space Studies Board.
"I have been struck from the very beginning that this was a project that could easily be dismissed as science fiction," Smith said. "However, all the scientists we have spoken to about this have required very little persuasion that this was a worthwhile project."
Boxed in beliefs
"We need to get a real understanding of what carbon is capable of in terms of life," said Michael Meyer, Senior Scientist for Astrobiology here at NASA Headquarters.
"We don’t want to end up just focused on only looking for DNA-type molecules ... but we do want to look for anything carrying information that is carbon-based."
Meyer said the meeting will bring together some of the brightest minds. Their duty is to think outside the biological box that is the norm. Those discussions can help NASA build the right tools that have the potential of finding something unexpected, he said.
"You have to keep in mind ... we know what life is on this planet and we still haven’t figured out how it got started. We have the basic ingredients ... but it has proven to be a difficult problem for something that we know exists," Meyer said. "So if you’re going to start looking at things that we don’t know exist, you don’t want to try every possible scenario. You want to make sure you look for things that are reasonably possible."
Search for life ... on Earth
There are two things that astrobiology does, Meyer said. One is that it forms the intellectual foundation for our understanding of the potential for life elsewhere in the universe. Part of this intellectual effort is to determine -- as is the case for Titan, a moon of Saturn -- whether or not life is possible there, theoretically.
The other half of the astrobiology effort, Meyer said, is to help guide what kind of life-detection instruments should be made.
"We’re going through a tremendous biological boon in learning so much about life on this planet. A lot of this advancement is due to remarkable techniques that have been developed that are extremely sensitive, but also highly specific," Meyer said.
"But that very sensitivity, because of its specificity, makes it almost useless in the quest to look for life elsewhere. That is, unless life elsewhere is made of exactly the same building blocks that were made out of and using similar sequences. So what we need to do is come up with more general ways to look for life ... but increase the sensitivity in order to find that life," Meyer noted.
There is an interesting twist to the search for life elsewhere in the cosmos. You might stumble on previously unknown life right here on Earth.
"If we come up with techniques, knowing the organisms that we’re looking for, we might find some organisms here on Earth previously not known, much less finding things on other planetary bodies," Meyer said.
"I think this kind of topic has always grasped human imagination," said Dirk Schulze-Makuch, Assistant Professor in the Department of Geological Sciences at the University of Texas, El Paso. "Now, finally we begin to have some understanding what kind of expectations and constraints on possible extraterrestrial life are reasonable," he told SPACE.com.
The timing is especially suitable, Schulze-Makuch said, because the NASA Cassini spacecraft will arrive in the Saturnian system in July, with Europe’s Huygens probe to be released onto Titan in early 2005.
"Titan is the ‘weirdest’ of planetary bodies in our Solar System -- meaning different from Earth -- possessing hydrocarbon surface bodies and methane rain. Thus, if life would have gained a foothold on Titan with environmental conditions so different from Earth, it should be ‘weird’ indeed, and should function differently in many ways than we experience life on Earth.
Schulze-Makuch will take part in the upcoming workshop, outlining possible microbial habitats and metabolisms on Titan.
"This is an important workshop," said Jonathan Lunine, Professor of Planetary Sciences and of Physics, and chair of the Theoretical Astrophysics Program at the University of Arizona in Tucson. He is a guest presenter at next week’s meeting.
"In the search for life elsewhere in the solar system, we tend to plan for life as we know it…even down to the nucleic acid bases or base sequences used in organisms elsewhere," Lunine said. "What if they don't use DNA? Or RNA? Or linear information-bearing polymers? Do they have to use liquid water as the universal biosolvent?"
The universe has surprised us before with its variety, Lunine added, in spite of the simplicity and small number of fundamental physical laws.
"Yet our imagination hasn't been very good at envisioning how strange or unexpected life might be," Lunine concluded.