for Astrobiology Magazine
Moffett Field CA (SPX) May 12, 2010
The 2010 Astrobiology Science Conference recently was held deep in the heart of Texas, near NASA's Johnson Space Center. The famous line "Houston, we've had a problem" could've been a tag line for the conference - except the "problem" in this case was not a wounded Apollo 13 spacecraft, but the puzzling and ongoing search for answers about the origin and evolution of life on Earth and the possibility for life in the universe.
The conference portions were Texas-sized, with more science presented than any single space cowboy could lasso. Here are a few Lone Star stand-outs:
Primed for Life
The famous Miller-Urey experiments of the 1950s showed that amino acids could be produced under early Earth conditions, simply by adding a spark of electricity. However, concepts of what the Earth's environment was like at the time of life's origins have changed since then.
The original Miller-Urey experiment presumed a reducing atmosphere (with gases like H2O, CH4 and NH3), but it is now thought that the Earth's atmosphere was instead dominated by gases like N2 and CO2.
With this type of neutral atmosphere, amino acids aren't produced as readily by simulated lighting. Still, Hud said that recent experiments have shown that large amounts of amino acids could be produced from neutral gas mixtures.
Hud also noted that in 2008, scientists re-examined products produced by a less famous Miller experiment in which hot water mist was used to simulate a water-vapor-rich volcanic eruption on the early Earth. The team found that Miller's volcanic experiment actually produced a wider variety of amino acids than the classic Miller-Urey experiment did.
For anyone who wants to try to create life in the lab, this is Hud's recipe for life's origin:
1 part HCN 1 part formaldehyde 1 part salt 0 to 100 parts H2O Cycle water content daily between 0 and 100 activity by evaporation and rehydration cycles, then allow 103 to 108 hydration-dehydration cycles for first sign of self-replicating molecules.
Lava Tube "Bug Poop"
These deposits were thought to be the result of purely chemical processes, but according to caving mavens Penny Boston of New Mexico Tech and Diana Northup of the University of New Mexico, many of these patterns are actually "bug poop" left behind by microbes as they eat away at rock walls to obtain nutrients.
"A lot of morphologies that we might have overlooked in the past, that look very mineral, actually have a rich biodiversity," said Northup. With their colleagues, Boston and Northup are using computer models to simulate the pattern formation. By narrowing in on the specific biological processes responsible for creating them, they can learn how long these patterns persist and remain detectable as biosignatures. These understandings, they hope, will one day prove valuable in robotic life detection efforts in lava tubes on other worlds.
It's Miller Time
Charles Cockell of the Open University in the UK explained that life on these bare rocks is mostly cyanobacteria, and studying them may tell us about the limits for life on other planets. What are the different mechanisms the cyanobacteria use in order to survive where few else can? One thing's for certain - if anyone could use a beer after a hard day, it's the life on sea cliffs in Beer, England.
Lineweaver disagrees with scientists such as Simon Conway-Morris, who believe that certain body forms - wings, eyes, brains - arise again and again because those are ideal solutions that biology has devised to interact with the environment.
This theory of convergence, says Lineweaver, is flawed because it ignores the fact that life on Earth shares certain genes, and those genes are the foundation for what bodily forms can eventually develop. For instance, people often point to dolphin brain size as an instance of convergence with humans.
Lineweaver says such a claim is ridiculous because it ignores the fact that 60 million years ago, humans and dolphins diverged from a common ancestor.
A Warm and Wet Mars?
Jim Kasting, however, believes that many of the features identified on Mars would have taken much longer to form. One primary example that Kasting used was Nanedi Vallis on Mars, which Kasting referred to as "essentially a Grand Canyon, on a slightly smaller scale." Kasting estimates that it took roughly 5 million meters of water to form the Grand Canyon on Earth over 17 million years.
On Mars, Kasting says one hundred thousand times more water would have been needed to form Nanedi Vallis than what would have been generated by an impact. Kasting and Toon also discussed problems with the greenhouse models of Mars, and why some scientists don't think such an atmosphere would have warmed the planet.
More carbon dioxide would have raised the temperature, but more clouds would have reflected sunlight back into space, cooling the planet. Toon noted: "We've spent 30 years on the greenhouse effect and no one has solved the problem in a credible way so far. On the greenhouse problem we're just drifting into deeper and deeper complexity."
TWEEL to Reel in Mars Life
TWEEL (Twin Wireless Extraterrestrial Experiment for Life) would consist of a set of sterilized dart-like probes that would contain two chirally distinct sets of nutrients, in different chambers. (Life's building-block molecules come in right- and left-handed, or "chiral" versions, but life's basic structures incorporate only one chiral alternative of each: L ("left-handed") amino acids and D ("right-handed") sugars.)
Shot downwind to prevent contamination, upon impact TWEEL's darts would release the nutrients into the soil, radioing results back to the lander. If only one of the two sets of chiral nutrients induced a reaction, Levin said it would be nearly incontrovertible evidence of life on Mars.
Bringing Back the Right Stuff
"We can now move into the next phase - seeking signs of life." One way to do this is to bring a sample of Mars rock and soil back to Earth for laboratory analysis, allowing researchers to employ far more sophisticated tests than would be possible to include on a spacecraft. Decadal survey chairman Steve Squyres got some serious pushback from the audience when he reported that the overwhelming consensus within the Mars science community was that sample return should take priority over testing for life on Mars (in-situ tests). Among those who argued in favor of in-situ testing was Carl Pilcher, former senior scientist for astrobiology at NASA headquarters and current director of the NASA Astrobiology Institute.
"There is something wrong," he said, with trying "to determine the answer to the most important question about Mars from a kilogram of Mars" - the amount of martian rock and soil that could be brought back to Earth - without first conducting life-detection tests in "a bunch of different places" on Mars to determine which material to bring back.
Although much of the discussion about upcoming missions focused on cost constraints, Joe Levy of Portland State University also argued for the less-costly in-situ experiments first, pointing out that once a strong indication of life has been found on Mars, "I guarantee you there will be money to bring the samples back."
"The 'ignorosphere' is too high for aircraft and weather balloons, and too low for satellites," Grinspoon noted. Commercial reusable suborbital spacecraft therefore could be used not only for space tourism, but to help scientists gather valuable information. The frequency of tourist flights also could allow scientists to reliably test and certify new instruments for astronomical and planetary observation.
And by the way, if do you hope to fly as a space tourist, the projected total flight time is 2.5 hours, but the total time spent weightless is just 5 minutes.
At 1/20 a person's normal metabolism, only 10 days worth of supplies would be needed for a 200-day space flight. One problem, however, is that freezing can cause crystals to form in body fluids, leading to massive cellular destruction. Cryogenic solutions could be used instead, but then you have problems with chemical toxicity. Astronauts will not be able to sleep their way to the next star system quite yet.
Tests of the pristine snow showed few if any microbes were released into the surrounding environment from the vehicle, and Schuerger said this means that elaborate pre-sterilization procedures for space exploration vehicles may not be necessary. Even astronauts walking outside their rovers on Mars won't need to fret - all the contamination would be on the inside of the spacesuit, while the outside of the suit would be continually sterilized by UV radiation.
Aliens 20 Light Years Away?
Dirk Schulze-Makuch of Washington State University said that based on the type of star and the location of the planet's orbit, Gleise 581d is comparable to Mars. However, Planet "d" is between 7 to 13 Earth masses, and this greater mass means the planet could have volcanoes, a magnetic shield, a thick atmosphere, water oceans - and potentially life. While its massive size may make it an Earth in a Mars orbit, its bulk may give it some unique qualities. "Gliese 581d would have more gravity than us, so its life may tend to crawl rather than fly," Schulze-Makuch noted.
A False Positive for Life
UV radiation can also create O3 by breaking oxygen molecules free from other gases (a process called photodisassociation, or photolysis). It's a slow process to build up ozone this way, especially because UV light can simultaneously be destroying the O3 molecules as they're making them. But, like a dripping faucet eventually filling a sink, ozone levels could build up over time. This kind of ozone accumulation could be detectable, and therefore could potentially fool us into thinking an extrasolar planet has life.
The Future of Astrobiology
He imagines a world where private companies will play a role in exploring our solar system in searching for signs of life. Wealthy patrons of astrobiology will get tired of waiting for answers to questions like "Is there life on Mars or Europa?" The resources of these private (and impatient) individuals may help scientists explore some of the most astrobiologically significant locations in near and far space. By 2060 - Voyage to Alpha Centauri!
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