At 2pm EST on Thursday December 2nd, the astrobiology department of NASA are going to be holding a news conference. What they are going to be announcing from NASA Headquarters in Washington (with simultaneous online streaming and a broadcast on NASA's satellite TV channel) is billed as "an astrobiology finding that will impact the search for evidence of extraterrestrial life."
Remarkable stuff, but what exactly are we to expect? Does this mean that we will be hearing a definitive report that life exists on other planets in our solar system? Maybe, but probably not, is the short answer.
Does Titan have life?
What seems most likely is that NASA will be announcing that Saturn's largest moon, Titan, is showing promising evidence of the preconditions to a strange form of life. To be more specific, given the research specialties of the assembled scientists, we could be looking at biochemical conditions favourable to development of microbes engaging in something called anoxygenic photosynthesis.These micro-organisms (or their chemical precursors) could exist somewhere within a layer of liquid water beneath Titan's surface. This is a process similar to what has been hypothesized may have happened in the early stages of the formation of life on Earth. At this time in our planet's development, the conditions around hydrothermal vents on the ocean floor are thought to have been particularly favorable to the emergence of life.
This is somewhat different from the process of photosynthesis that we are familiar with from Earth's vegetation today. For example, Arsenic, rather than Phosphorus, is the basis for its chemistry. The building blocks of this form of life may be different, but the underlying biochemical processes at work are very similar in many ways. Similar enough that NASA's astrobiologists are assembling their heavy hitters, including the director of NASA's astrobiology department, Mary Voytek, and NASA Astrobiology Research Fellow Felisa Wolfe-Simon, to present their findings about Titan to the world.
Dr. Felisa Wolfe-Simon achievements include "(extending) our understanding of the molecular evolution and phylogenetic radiation of the Mn and FeSOD isoforms in photoautotrophs" which, in less technical terms, is considered to have expanded our understanding of the mineral potential for the origins and evolution of Earth and the life on Earth. The specialty of other experts on the panel includes geobiologist Pamela Conrad, who has written a paper about the possibility of life on Mars, and ecologist James Elser, a specialist on the chemistry of environments where life might evolve.
Arsenic-based life
In her research, Wolfe-Simon and her coauthors have assembled what she calls "(a) plausible TESTABLE hypotheses regarding the likelihood of life arising to either originally incorporate arsenate in a functional sense, and/or more speculatively, alternative forms of life utilizing a genetic system entirely based on arsenic."
Dr. Ronald S. Oremland, one of Wolfe-Simon's principal research partners, has been fascinated by the chemistry of emergent pre-conditions for life since he was an undergraduate. In one test paper, his professor asked the question: "If you were asked to speculate about the form extra-terrestrial life on Mars might take, which geomicrobial phenomenon might you select as a model system?" At the time, he found this idea simply too interesting to answer in the exam for fear that he wouldn't be able to drag himself away and answer the other questions. So he ignored it.
In their paper "Arsenic in the Evolution of Earth and Extraterrestrial Ecosystems," one of the conclusions Orenland and Wolfe-Simon (and their co-authors) draw is that "it is not entirely unlikely for arsenic-driven anoxygenic photosynthesis to be a very real possibility in our solar system or other reaches of the Universe." Answering the original question asked by Orenland's professor some forty years later.
The discovery of the century?
Effectively, if Orenland and Wolfe-Simon's theory is correct, she and the team at NASA may have discovered the basic pre-conditions for life! Not just the pre-conditions for life on Earth, but also the microbial conditions that would be optimal for the emergence of life on other planets as well. On Thursday we will be hearing what they have found on Titan. Given the line-up of scientists involved, and the fact that Science magazine will be featuring a major article, the announcement should hopefully not be insubstantial.
Weird life: them or us?
Felisa Wolfe-Simon hypothesizes that early life could have taken an alternate biochemical pathway and that this might result in a "shadow biosphere." The idea is that a whole paradigm of life could emerge that is based upon arsenic, rather than the phosphate-containing organic molecules that are common to all the life forms we currently know. Scientists are calling this possible alternate, "weird life" (as if life wasn't weird enough as it is!). There is nothing in the biochemical facts of evolution that necessarily entails life should evolve in the way it has here on Earth. There could be alternative scenarios. In fact, these alternates may be more common than we are!
The big question is, if arsenic-based life is possible, or exists, is it a genuinely independent biogenesis, i.e., does it represent a second tree of life? One mind-blowing possibility is that this "weird life" is actually the commonest form of life out there! If this is a genuine distinct evolutionary pathway from the one life on Earth eventually took, because arsenic's qualities, under certain conditions, are considered bio-chemically more favorable than phosphorous for the creation of enzymes, it could be the more common route that evolution takes on other planets.
If this is the case, the possibility exists that life could be both much more widespread across the galaxy and also much more diverse than previously expected. We know that when organic-based life reaches the complexity of developing a cell nucleus ("eukaryotic life"), something happens to it. The following evolutionary developments (in comparison to the extreme diversity that simpler "prokaryotic" life forms display) are actually very similar to one another. Hence, if we are looking for organic molecules based on phosphorus, we could anticipate those life forms might be reasonably similar to us.
If arsenic-based life is a reality, it is life on Earth that could well turn out to be the "weird life" out there. It is possible that the type of life that has developed in our biosphere is rare and unusual. It could be that we are the exception to the rule, rather than the norm. It is even possible, if this research proves correct, that we are about to discover ourselves surrounded by a myriad of totally different extra-terrestrial genealogies, so far removed from our genetics, that they make reptiles and mammals look like the closest of cousins. It has even been suggested that these different forms of life may be able to use different energy sources from "standard life," including ultraviolet radiation.
Shadow Biospheres
Alternately, it may turn out that "shadow biospheres" are "merely a highly divergent outlying branch on the same tree as familiar life," or just a stage that life goes through on the way to phosphorous-based organic complexity. Another possibility is that the evolution is, in fact, convergent as it progresses, whatever its molecular origin. This, in itself, would be a stupendous discovery.
It cannot be ruled out that arsenic-based life has "discovered" solutions to the same evolutionary problems, as phosphorus-based life has had to overcome in its development. This means that advanced and complex life forms may well emerge in these alternate forms of biogenesis too. This dramatic implication of that is that life may not be "one thing." It may instead be that life doesn't have one source, but many origins. Life, rather than one family tree, may be a forest of individual trees.
If there are the preconditions for, or the existence of, life in the water deep under the surface of Titan, it is also quite possible we may find it on similar icy moons. Christopher Sotin, a Senior Research Scientist at the Jet Propulsion Laboratory, has been studying the internal dynamics of these moons. His conclusion is that a liquid water layer is present in the interiors of three of Jupiter's largest moons, Europa, Callisto and Ganymede, as well as another moon of Saturn, Enceladus. We now know that Enceladus definitely has water in its interior. NASA's Cassini spacecraft swung within 200 miles of its surface and photographed giant geysers of water hundreds of miles long emerging from its south pole! On Enceladus, pockets of liquid water may be just hundreds of feet from its surface in certain places and there are also signs of geo-thermal activity. We may be outnumberred even in our own solar system!
Is there anyone out there?
So the question about Thursday's press conference is will NASA announce the existence of extra-terrestrial life? Or will they just fudge it and say something like "the possible pre-conditions for the emergence of life"? The best we can probably expect is that the analysis looks promising for the existence of arsenic-based micro-organisms on Titan. An outright, "yes, there's life on another planet" seems unlikely. Especially given that a popular alternative acronym for NASA is "Never A Straight Answer."
However, the announcement of "a breakthrough" should mean we will be hearing something substantial. If the NASA astrobiologists did announce that life on Titan looks possible, or even likely, the consequences would be enormous. The notion that Earth is the only planet with life on it would be gone forever. Psychologically for the human race, the fortress of "Island Earth" would have fallen. Even if we are just sharing the solar system with some arsenic-loving microbes, the fact is "We are not alone." (Mulder and Scully may well be a little disappointed though, as these life forms may turn out to resemble blue-green algae, or cyanobacteria, more than they do the typical "extra-terrestrials" featured on The X-Files.)
Having found life once, we are much more likely to start finding it in other places. Even if NASA's announcement is only tentative at this point (and don't be surprised if its totally non-committal), it could well equal, or surpass, the popular impact of the moon landings. Our place in the universe will have changed forever. There is other life out there after all!
The NASA news conference is at 2pm EST, tomorrow, Thursday December 2nd. It can be streamed live here.For more information on the research of Dr. Felisa Wolfe-Simon, go here. The papers mentioned in this article can be accessed from here.
Mark Heley is the author of The Everything Guide to 2012.
Image by FlyingSinger, courtesy of Creative Commons.
