We may owe our earthly existence to the transitory conditions of early Mars. Research reported this week by NBC News, Huffington Post, and other sources gives new weight to the notion that we all started out somewhere else. The effect may be to alter our view of life anywhere in the universe.
Panspermia is the theory that life began somewhere else in the universe and came to Earth on meteorites. The idea isn’t new – the notion goes back to the ancient Greeks – and life did emerge about four billion years ago, soon after a period of heavy meteorite bombardment. But the universe is big and hostile, so trying to draw a scientific line between all of space and our own planet isn’t easy.
Dr. Steven Benner, a geochemist with the Foundation for Applied Molecular Evolution, has given that line an origin. Dr. Benner claims that early Mars offered chemical conditions that not only made life possible there, but that solved some of the difficulties with life conditions on early Earth.
At some point, organic molecules had to combine to make the more complex molecules essential to life on Earth: RNA, DNA, and proteins. Early Earth had no shortage of energy and water, but both of these conditions made life harder, not easier. Energy turns organic molecules into a tar-like substance (the Tar Paradox) and water can actually be corrosive to DNA and proteins (the Water Paradox). If life emerged on its own, the cards were stacked against it.
So, was there an easier path to success? Dr. Benner thinks so, and believes that the path originated on Mars, where chemistry might have been different.
It turns out that at least two elements, oxidized molybdenum and boron, can mediate the processes that work to decompose organic macromolecules. Early Earth didn’t have much oxygen for this kind of molybdenum to form, but Mars did. Boron has also been found in Mars meteorites. And, while Mars likely had water (confirmed recently with evidence from the Mars rover Curiosity), there was less of it on Mars, which would have given organic molecules a better chance to form life there than on Earth. Volcanic eruptions or meteoritic collisions on Mars could then have sent that life traveling.
Times and conditions changed on both planets, of course. Mars became less habitable, jeopardizing any life that existed there, while Earth became more life-friendly. Life emerges in one place but survives in another. A lucky legacy for us, if the model is correct. The explanation gives the panspermia scheme at least one physical origin, addresses several difficulties in the organic chemistry of early Earth . . . and is testable.
There will certainly be debates about Dr. Benner’s conclusions. While the current evidence isn’t conclusive, though, better information may be coming. A tool to detect RNA and DNA in Martian soil samples is being designed for use on the Mars Explorer Rover mission scheduled for launch in 2020. For now, many scientists concede that his theory is at least plausible.
It’s interesting to recognize the importance of time in Dr. Benner’s model. Most panspermia explanations tend to ignore a role for temporal factors; transport either occurs or it doesn’t. The new explanation makes time a big player in the process. Conditions on the donor and receptor planets change over long timeframes, and timing of the “handoff” can make or break the chain of life.
Panspermia can ever be proven, of course. Alternative processes can always be proposed. If this work is confirmed with new evidence, however, then panspermia has at least one good case study. How would that change our thinking about ourselves and everything around us on Earth? Would the definition of “alien” have any meaning anymore?
Ray Bradbury asked this question in the last story of his Martian Chronicles. Maybe we’ll have to choose our own answer soon.