Some scientists think humans descended from Martian microbes
Astrobiology sounds like the stuff of lava lamps and Jetsons reruns.
Yet seven years after NASA launched a formal astrobiology research program, scientists of every stripe — geologists, biologists, chemists, paleontologists, oceanographers and astronomers — have rallied to the quest.
They've spent as much as $65 million a year trying to solve a mystery that has underpinned religion and inspired thinkers from Seneca to Carl Sagan: How did life on the lonely Earth begin? And is Earth really the only source of life in the universe?
With the help of modern tools such as the genome, high-powered computer modeling and robotics, they're finding some out-of-this-world answers, ones that may lead to Mars and beyond.
During an astrobiology conference in Washington last week, scientists debated the newest evidence and worried that funding for the National Aeronautics and Space Administration is vaporizing, just as their cross-disciplinary work is unearthing extraordinary discoveries, such as the organic matter in bits of Jovian comet dust recently collected by NASA's Stardust probe.
Many scientists favor the theory that life began as oxygen-loathing microbes in superheated deep-sea vents 3.8 billion years ago, when water probably covered the planet. Others suggest life's assembly could have occurred along the crystal face of damp volcanic rock.
And then there is the theory known as panspermia. Once the province of science-fiction novels and cartoons, the notion that the vital ingredients of life came from outer space has garnered respect from some lofty places of late.
A few scientists think there's evidence that humans actually descended from Martian microbes, not exactly what the author of Men are from Mars, Women are from Venus had in mind.
But it merits further study, said chemist Steven Benner, who has founded a new institute in Gainesville, the Westheimer Institute for Science and Technology, which aims to bridge chemistry and biology, with evolution as its guide.
"If you really want to find a place to get life started, it's Mars, and if you want to get a place to get life to flourish, it's Earth," Benner said.
While at the University of Florida a few years ago, Benner's team collaborated with scientists at The Scripps Research Institute to explore what kind of chemistry is necessary to support life.
In the process of trying to synthesize a living, evolving molecule in his lab, Benner seized upon minerals containing the element boron, the substance that makes some fireworks glow green.
Was boron the ingredient that enabled the Earth to go green as well?
Benner found that boron, with calcium at hand, had the talent of helping hold together the chain of carbon needed to stabilize a ribose sugar, the backbone of ribonucleic acid, the scaffolding for our genes. Without boron and calcium, heat, water and lightning would cause ribose to disintegrate into a tarlike mess, unable to support genes.
For geologic reasons, Benner's boron finding points directly to Mars as a likely source for Earth life, said Cal Tech geobiologist Joseph L. Kirschvink.
"When Steve told me of his work on ribosynthesis with boron, I said, 'Steve you've just proven to me that we're Martians.' "
That's because the boron needed to make ribose must come as calcium borate, a mineral that's soluble in water, Kirschvink believes.
A few places on Earth, including Death Valley, have a good supply of calcium borate, but they were under water at the time the first evidence of microbes appears on Earth, Kirschvink said. That was not the case on Earth's nearest neighbor, Mars, which was sending off bits of rock and dust in the Earth's general direction every time it took a hit from a meteorite.
"We know we have about a ton of Martian rock coming in a year," Kirschvink said. "And it wouldn't take more than a few spores to seed the Earth with life."
Could Mars possibly have had spores?
Space exploration and powerful telescopes have revealed that the red planet has polar ice, just like our own planet. In 2004, NASA's Opportunity rover found evidence that it once had liquid water running across its surface.
And 3 billion or 4 billion years ago, at the time when the Earth apparently was covered with water, Mars may have had a warmer atmosphere and abundant microbial life.
"It's entirely reasonable that there was life on Mars, but maybe long extinct," said Gerald Joyce, a professor at Scripps in La Jolla, Calif., who has collaborated with Benner. "The way to find it is to go there, drill down a bit, bring back samples to Earth and look at them."
Unfortunately, a plan to do just that has fallen victim to NASA budget cuts.
"It's very sad," Joyce said.
Plus, President Bush's budget request to Congress for next year proposes slashing funding for astrobiology research in half.
Kirschvink fears religious sentiment may be playing a role in the money cuts.
"There are fundamentalists who don't like the idea that their creator put life anywhere other than Earth," he said.
In the meantime, Joyce and other scientists are going as far as they possibly can with their science here on Earth.
In the journal Chemistry & Biology, Joyce's lab describes using evolutionary principles to convert RNA into DNA and keep its chemical activity intact.
Such conversion may have been necessary for more advanced life to evolve. It's one more clue as to how life might have assembled, Joyce said.
Meanwhile, the Marsophiles are excited about a new paper from Martin Fisk, a University of Oregon marine geologist. Fisk has studied several pieces of Martian meteorite, including one called Nakhla, donated from the Smithsonian Institution. In the journal Astrobiology, Fisk describes finding tunnels etched into the Martian rock — tunnels just like ones he has seen in Earth rock. On Earth, only microbes cause those types of tunnels.
"They are not known to be made by any other process that we know of," Fisk said.
It's a controversial notion, one that has been debated since 1996, when another bit of Martian meteorite stored at NASA labs near Houston was found to contain organic material and what appeared to be fossilized microbes.
At the time, critics shot down the idea, insisting that inorganic activity might have made the marks in the rock.
Fisk notes that his samples contained no DNA, the code for life.
Benner thinks it's not a deal-breaker.
"The failure to find DNA in the Martian rock is assumed to argue against Martian life. But this logic is coherent only if Martian life must use the same type of DNA as Earth life uses," Benner said.
Kirschvink agreed. "DNA would not survive 4 billion years, even on Mars," he said. "It barely survives in frozen mammoths that are only 12,000 years old."
For now, there are more skeptics of Mars' seeding life on Earth than there are advocates.
Conel Alexander, a geochemist with the Carnegie Institution of Washington, suspects life arose organically on Earth.
"The worry is nobody really understands how well microbes would survive the shock that is required to put something into orbit. To knock it off Mars, how would it survive the radiation? That's one of the many questions," Alexander said.
"Nonsense," retorts Kirschvink. "The European Space Agency demonstrated more than five-year survival to space conditions, and some of the Martian meteorites get here within one year of a major impact on Mars."
Matt Schrenk, a geobiologist at the Carnegie Institution, favors the deep-sea vent theory, although he's not ruling anything out yet.
"The simplest explanation is that life started here," Schrenk said. "This is the one place where we know life does exist on Earth. But I think as evidenced by this Stardust mission, there's plenty of organic material coming in constantly from space. That must have played some role in the origin of life on Earth."
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