Arsenic-based life and Astrobiology

3 07 2012


It’s been some time since the controvertial announcement that “arsenic-based life” had been discovered on planet Earth.  With time, however, the less-sensational reality of the discovery has been made more clear, and I think it is sensible to review the current state of the research as it relates to the biochemistry of life and the idea of “alternative” biochemistries.

An Imminent Announcement

NASA "meatball" insignia 1959–82 and 1992–presentThe recap: Making some serious waves back in November of 2010, NASA released a media advisory stating that a news conference would be held days later that would reveal “an astrobiology finding” that would “impact the search for extraterrestrial life.”

The journal Science strictly embargoed details until the news conference was held.

Of course, the internet went bezerk.  NASA’s announcement, the first of its kind since the announcement of potential bacterial fossils in Mars meteoriete ALS-84001, seemed to hint to many that a rover had finally hit paydirt.  Signs of extraterrestrial biology had finally been found!

However, the rampant speculation that followed only fueled an initial spike of disappointment with the actual announcement: that young biogeochemist and astrobiologist Felisa Wolfe-Simon led a research team that discovered, as was popularly-reported, “arsenic-based” life here on Earth.

Wolfe-Simon’s discovery was  published in the journal Science and was actually met with a fair degree of sensationalism right out of the gate, followed by sharp criticism that survives to this day.

File:GFAJ-1 (grown on arsenic).jpg

Magnified cells of bacterium GFAJ-1 grown in a medium containing arsenate. (Credit: NASA)

GFAJ-1: The Arsenic Experiment

A critical question of astrobiology is whether or not life is required to take advange of the same chemistry we do, i.e., that our biochemistry is the only biochemistry that works.  If other types of chemistry were available to life, (such as silicon-based life hypothesized on Saturn’s moon Titan,) then this implies that opportunities for life elsewhere in the universe are great in number.

If not, then life may be more rare; waiting for the perfect “goldilocks” conditions before it can arise.

Testing this hypothesis, astrobiology researchers have been pressing for evidence of so-called “shadow biospheres,” or examples of life taking advantage of different or exotic chemistries right under our own noses.  In other words, seeking out environments where life might have evolved out of necessity to take advantage of different, ordinarily toxic chemical elements is one strategy to investigate the question here at home.

With this objective in mind, Wolfe-Simon (and colleagues) proposed that instead of phosphate (PO4), life might find a way to substitute arsenate (AsO4, depicted in the header)  into its DNA.  Specifically, by isolating an extremophile (an exotic bacterium) from the bizarre ecosystem at work in the alakaline, salt-ridden, and arsenic-laden Mono Lake, Wolfe-Simon’s research team claimed success: the identification of an organism that was capable of substituting arsenic for a small percentage of its phosphorus!

Clarifying “Arsenic-based” 

Wolfe-Simon’s findings, which were obtained when the GFAJ-1 bacteria were grown in a culture doped with arsenate, are more accurately described as identifying a potential “arsenic-utilizing” as opposed to “arsenic-based” form of life.  Even so, the results were considered a boon for those proposing widening the technical search for extraterrestrial life.  In this view, should life be utilizing very different biochemistry than what we’re accustomed to, it is possible that the instruments on our rovers, etc., might not even detect it (or recognize what it was that was being detected).

However, the results have been hotly-debated since, and more recently, have been outright cast into doubt when researchers just this year used a separate analytical method and failed to detect arsenic in the GFAJ-1 bacteria.

The Take-Home

The jury is still out considering whether or not we’ve actually detected so-called “alien” biochemistry or hard evidence of a shadow biosphere.  That having been said, the justification and approach is still in my opinion a solid one.

It remains within the realm of possibility that extraterrestrial life (or terrestrial life under extreme conditions) might, due to opportunity or necessity, be chemically different from our own.

Food for thought.


Xenoarchaeology: Reality and Fantasy

3 05 2012

Archaeological evidence of extraterrestrial involvement with ancient human civilizations, as seen in the movie, “Prometheus.” (Credit: Fox)

Cultural Xenoarchaeology

For reasons I can’t immediately explain, (the recent rash of technical publications addressing the concept of “xenoarchaeology” or “non-terrestrial artifacts” nonwithstanding,) there is a tantalizing idea cropping up in a number of recent and upcoming films and television programs.  (See: Indiana Jones and the Kingdom of the Crystal Skull, Prometheus, Ancient Aliens.)

This concept, simply, involves the discovery of archaic evidence of the existence of Extraterrestrial Intelligence (ETI) and/or evidence of physical interactions of ETI in Earth’s (and mankind’s) past.  All of this, arguably, might be lumped under the auspices of the protoscience Xenoarchaeology.

Perhaps this increase in popular consumption of the idea that aliens have been around longer than we have indicates a mounting social awareness of cosmic deep time and the possibility of extraterrestrial life as it is stirred together with our classic, collective existential questions: “Why are we here?” and, “Are we alone in the universe?”

However, these pop-culture expressions and depictions of xenoarchaeology stray pretty far afield of what “scientific xenoarchaeology” would actually look like.

Separating Xenoarchaeology Fiction from Fact

In most part built upon ideas originally popularized by Erich von Daniken decades ago, (and fictionally by H.P. Lovecraft before him,) these modern concepts invoke the assistance of ETI in the development of human civilization as the “gods” of the religions and mythologies of antiquity.  However, this view has long since been shown by archaeologists to be entirely speculative and lacking in any direct, physical supportive evidence, (i.e., it is pseudoarchaeology.)  This stands in contrast to the physical archaeological evidence that does exist to directly support the idea that we humans created civilization, agriculture, the pyramids, etc., without need of assistance.

While the idea of meddlesome, elder-brother or mentor-type ETI is admittedly thrilling, the concept as it relates to xenoarchaeology does not automatically become scientific and in fact differs significantly from the groundwork currently being laid out for scientific xenoarchaeology.

Allow me to provide a few examples of where reality and fantasy diverge:

  • The practice of much fictional xenoarchaeology takes place on Earth, whereas future scientific xenoarchaeologists will likely find their skills of most utility on other worlds during in situ investigations.
  • Fictional/pseudoscientific xenoarchaeology typically centers on terrestrial features of human civilization, (e.g., pyramids, temples, large-scale geoglyphs,) whereas proposed xenoarchaeological investigations will likely center on extraterrestrial features of a possible artificial nature on other worlds.
  • Fictional xenoarchaeology usually assumes the involvement of ETI with a given feature of interest and works from there, whereas scientific xenoarchaeology will be required to rule out all other natural planetary, biological, and geological possibilities before hypothesizing ETI.  (In fact, ruling out features as xenoarchaeological in nature and disproving those making pseuarchaeological claims will probably be the most frequent uses of the existence of a true, scientific practice of xenoarchaeology.)
  • Xenoarchaeologists of popular fiction conduct investigations with their bare hands, whereas scientific xenoarchaeologists will primarily use remote sensing techniques, (satellites, robotic rovers,) to investigate/collect data.  (Or, if they are very lucky, they might one day even conduct work from within a spacesuit or biological quarantine facility.)
  • Fictional xenoarchaeology attempts to find evidence of ETI in terrestrial archaeological sites or artifacts, whereas scientific xenoarchaeology will rely on the fact that ETI was not involved in terrestrial archaeological sites and artifacts in order to construct relationships and methodologies that will be useful in the evaluation of a potential site of completely alien/unknown character. 

I could go on, but hopefully the potential difference between xenoarchaeological reality and fantasy, (like popular depictions of most sciences,) has been made clear.

Why Xenoarchaeology at All?

When considering the concept of scientific xenoarchaeology, invariably the question arises: “Is there a need for xenoarchaeology as a science at all?” 

Admittedly, this question is a good one.  Pseudoscience aside, there are currently no pressing sites of xenoarchaeological interest.  Why, then, expend the effort?

Well, let me first point you to the established field of astrobiology.  This is a field devoted entirely to the origin, evolution, and possibility of extraterrestrial life.  Associated with the field are multiple related academic journals, societies, and even college degree programs. 

Astrobiology is legitimate.  Yet, we have yet to discover even the smallest extraterrestrial microorganism.  Yes – Astrobiology, the scientific study of alien life, is currently conducted in spite of the complete absence of the known existence of alien life.  The field thrives regardless.  Why?

Astrobiology thrives because its underlying assumptions are viewed to be scientifically sound.  Life occurred on Earth, and considering the pantheon of worlds being discovered around other stars, by all modern physical and biochemical reckoning, signs seem to point that it will only be a matter of time until we discover life elsewhere.  (By similar reasoning, the Search for Extraterrestrial Intelligence [SETI] continues its vigilant watch for technological [radio] signs of life in the galaxy, and few nowadays write off the pursuit as being in vain.)

The assumptions underlying the scientific development of xenoarchaeology are, indeed, indentical to those above.  And further, given the ambiguity of the term “intelligence” and modern knowledge of many cosmic threats that can cause mass extinctions, (novas, gamma-ray bursts, asteroid impacts, etc.,) it seems even more likely that material evidence of extinct extraterrestrial life will be encountered prior to the fortuitious discovery of life itself while it is still alive. 

That is, if I were a gambling man, I would wager that xenoarchaeologists get an opportunity to evaluate ultimately definitive evidence of extraterrestrial life prior to astrobiologists.

Xenoarchaeological Relevance

In the final analysis, popular depictions of xenoarchaeology are useful in that they engender a more sophisticated (if not completely sensationalized) view of our place in the cosmos and the possibility of intelligent life in it.  On the technical side, considering the current absence of evidence of extraterrestrial life, xenoarchaeology as a scientific pursuit is equally justifiable to astrobiology and SETI. 

Further, I would argue that like astrobiology, taking the time to rigorously conceptualize a scientific field tangential to those that exist but centered in an extraterrestrial context will help us see ourselves from a clearer scientific vantage; this will invariably serve to enhance our understanding of terrestrial archaeology, anthropology, biology, and yes, even astrobiology.  (Developing an additional means to address some of the planetary pseudoscience out there, e.g., Martian Cydonia, can’t hurt, either.)

And who knows?  Perhaps our space exploration investigations are only a rover or two away from the discovery of that first Martian or Titanean burrow or petroglyph, which history will remember as a moment that literally changes everything. 

My view is that it’d be far better in the event of such a discovery to be proactive and have scientific xenoarchaeology prepared, (in at least a cursory sense,) instead of being reactive and leaving the scientific establishment scrambling to catch up. 

In this sense, perhaps science could stand to learn a thing or two from Hollywood.

Xenoarchaeology Online

9 10 2010

I am excited to report that my article, “A call for proactive xenoarchaeological guidelines – Scientific, policy and socio-political considerations,” has been published online by the journal Space Policy as an in-press corrected proof as it awaits publication in an upcoming issue.  (I mentioned working on it previously in a post here.)

The thrust of the paper is that when you consider the galactic timescales and hazards we know to be in play against the evolution of alien life, we’re likely to discover evidence of life before we discover astrobiology itself.  Further, it’s only a matter of time before we identify suspected material evidence of astrobiological activity.  -And regardless of whether or not it turns out to be a real find, we should be prepared to investigate and evaluate it will the scientific rigor deserving of an actual find, with the foresight to successfully manage information verification and public dissemination.

The paper is a stab at highlighting the applicable scientific protocols, planetary pitfalls, and social snags a xenoarchaeological investigation might face in the hopes of stimulating discussion toward the development of a fully-fledged field of study.

Here’s to making it one step closer (academically, anyway) to the stars.  Feedback welcome.

UPDATE 11/2010:  The article has been officially published in Space Policy Volume 26, Issue 4, November 2010, Pages 209-213.

Differences between SETI, Astrobiology, UFOlogy

17 08 2010

Based on some recent feedback, I’m tempted to pose a question to the cyberverse:

  • What differences do you see, if any, between SETI (the Search for Extraterrestrial Intelligence), Astrobiology (study of locations and potential biochemistry of extraterrestrial life), and UFOlogy (study of UFOs)?

I ask this as a general point of discussion because some have expressed concern that working toward a preconceived methodology for xenoarchaeology, like I’ve been working on, will confuse Astrobiology, SETI, and the more pseudoscientific UFOlogy in the public mind.

So, what do you think?  Just how different is your perception of SETI, Astrobiology, and UFOlogy?  How legitimate a scientific pursuit are each?  How illegitimate?

Clearly, all three concepts are related.  Without Astrobiology, SETI and UFOlogy cannot logically exist.  UFOlogy implies “ETI,” but it makes some pretty incredible assumptions that in my mind remove it from the realm of hard science, or even speculative science, for that matter.

So, have at it.  Comments welcome.

Plant living on the Moon?

13 06 2010

Lunar Oasis project logo. Credit: ParagonSDC, Odyssey Moon LLC

If plans unfold as originally intended, one unexpected result of Google’s Lunar X Prize (which, like the original Ansari X Prize, is intended to spur private industry involvement in space development,) may be the transport and growth of the Moon’s first living plant.

Odyssey Moon Ventures LLC and Paragon Space Development Corporation announced a partnership in spring 2009 to create and deliver a lunar greenhouse.

Industry titan Paragon, a forerunner in space life support systems, is leading the charge with Odyssey, which was formed to compete for the Lunar X Prize, to create a “Lunar Oasis.”  This isn’t the first time Paragon has been involved with a project of this sort, as they’d previously designed a potential Mars sealed plant growth chamber for NASA’s Jet Propulsion Laboratory.

Lunar Oasis module prototype. Credit: Odyssey Moon LLC

The Moon is a particularly harsh environment, even when compared to Mars, and the the Lunar Oasis will need to protect its floral inhabitant(s) from solar and cosmic radiation while providing a temperate environment able to supply and manage nutrients, water, carbon dioxide, and oxygen.

According to their press release more than a year ago, the ideal astro-plant is from the Brassica family (of mustard fame), which needs only 14 days to complete a growth-seed cycle.

As fate would have it, this is also the length of a lunar day.

Now, we haven’t heard from the Lunar Oasis guys in a while, (more than a year,) and this may indicate that the project has fallen away, which would be a pity.  Projects like these, which capture the spirit and imagination – something familiar taking hold on an alien world – are exactly what we need these days to kindle the public mind to engage with private space.

Anyone else heard anything?

Target: Titan & Silicon-based life

18 03 2010

Move over, Mars.  According to new imagery from the Cassini spacecraft and new research recently published in the Journal of Cosmology, Saturn’s moon Titan may be the hottest exploration ticket in the Solar System.

Titan in front of Saturn. Credit: CICLOPS

Up until only five years ago, the massive moon Titan was one of the last great mysteries in our neighborhood of planets.  Itself bigger than the planet Mercury,  Titan’s freezing (-290 degrees!) smoggy, opaque, nitrogen-and-methane atmosphere was so think that we had no idea what its surface looked like.  It was only after the Cassini spacecraft settled into orbit in 2004 with advanced instruments that we were able to punch through the fog to see what was going on.

Radar images of Titan - dark areas suggest lakes/oceans of methane. Credit: CICLOPS

What we found was staggering.  Coastlines.  Erosion.  The most Earth-like environment to date.  As predicted nearly three decades ago but unproven until recently, Titan is the only other place in the solar system home to a hydrologic cycle of sorts.  I’m talking about lakes, streams, clouds, and rain.  But on Titan it isn’t water raining from the sky and running down mountainsides.  It’s far too cold, and water there is always a solid mineral, like silicon is here on Earth.  Instead, Titan’s “water” is liquid methane.

Utah? Rendering of possible Karst terrain on Titan. Credit: NASA/Malaska

While this is terribly good news for geologists interested in the processes of erosion (geomorphology), it was apparently bad news for hopeful astrobiologists.  Without liquid water, life as we know it can’t exist.  But hold that thought – Researcher Pabulo Rampelotto of Brazil’s Space Research Institute’s Exobiology and Biosphere Laboratory has identified an alternate biological chemistry that might support life on Titan…

Silicon-based Life

Our current understanding of physics, chemistry, and their roles in biology suggest that an organism could survive using an entirely non-carbon-based metabolism.  Silicon is a likely first place to look for alternatives.  Like carbon, (the chemical backbone of life as we know it,) silicon can form four bonds, stable bonds with itself and other elements, and long chemical chains known as silanes, which are very similar to the hydrocarbons essential to life on Earth.  Silicon is more reactive than carbon, which could make it optimal for extremely cold environments.

However, silanes spontaneously burn in the presence of oxygen, so an oxygen atmosphere would be deadly to any silicon-based life, and water as a solvent would be equally deadly for the same reason.  So, any environment with the potential for silicon-based life would have to be very cold, devoid of oxygen and water, but with another compatible solvent, such as liquid methane.  Sound familiar?

Of all places in the Solar System, Titan seems to be the only place active enough for life to currently exist.  -And even though Titan is definitely an alien and hostile place, it looks like we’ve identified a way for life there, as Crichton’s Ian Malcom famously put it, to “find a way.”


-Orion Nebula a Frothing Primordial Soup!

11 03 2010

HIFI Spectrum of H20 and Organics in the Orion Nebula. Credit: ESA, HEXOS

As astro-biochemists and astrobiologists have been suspecting for quite some time, the star-forming regions of space are literally teeming with the building blocks of life as we know it.  With just a few hours behind the Heterodyne Instrument for the Far Infrared, or HIFI for short, (which is currently flying aboard Europe’s Herschel Space Observatory,) researchers quickly obtained the highest-resolution infrared spectrum ever taken of the famous stellar nursery known as the Orion Nebula.

What they found blew them away: Not just blurred suggestions of organic molecules, but hard fingerprints of water, methanol, sulphur oxide, dimethyl ether, hydrogen cyanide, and others.

The case for the ubiquity of life appears to be getting stronger all the while, and with it comes a strengthened rationale for continued space exploration!

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