Why does Mars look like a good candidate for generating life on Earth? Steven Benner , the chemist who started the Foundation for Applied Molecular Evolution, “…presented the idea at a geochemistry conference last August (Discover Magazine June 2014 p. 22). Based on recent evidence, he believes life may have begun on Mars, “…then caught a ride on a space rock to our planet, where things evolved from there…”
Benner has focused on RNA as a likely precursor to life, a precursor to DNA, since it appears and self-replicates more easily from organic molecules. Since water disrupts RNA, Earth could have been less likely a place of origin than Mars, which was much drier. Also, Earth’s oceans could have diluted borate and molybdate so they could not stabilize ribose or reconstruct other sugars to make ribose.
Volcanic eruptions and meteors could have carried primitive RNA critters to Earth within nine months. Later, Earth was probably better at sustaining life that creating it, since its magnetic field could have protected life from solar radiation.
Chris McKay at NASA suggests that first we must find life on Mars. Its relationship to life on Earth may tell the rest of the story. I wonder how this fits in with the Irwin-Schulze-Makuch theory that Viking has already found hydrogen peroxide-based life there.
One of the Projects listed on syntheticbiology.org is the Minimal Cell Project (MCP). In a search of clues to astrobiology in alife studies, this project sounds more closely related to problems in astrobiology than some of the robotic studies or development of educable software, the hard and soft versions of alife work.
The site listed the Church, Forster and Luisi labs as active in the MCP. It published an interesting paper in August 2006 called “Toward Synthesis of a Minimal Cell” by Anthony C. Forster and George C. Church. (msb.embopress.org/contents/2/1/45) The paper declared that it is now possible to construct a “…chemical system capable of replication and evolution.”
Fed by small molecular nutrients and requiring only 151 genes, a stepwise “integration” of RNA, DNA and proteins has begun to build blocks leading to a life form. Safety is assured by creating a dependence on laboratory reagents and conditions for viability. The self-assembly is thought to be learned in a definite sequence that is “energetically favored.” Enzymes and the energy source are critical, as we know from extremophile studies.
In a 2010 article, M. C. Jewett and A. C. Forster (www.nebi.nih.gov/pmc/articles/PMC2952674/) agree with astrobiology concerns that synthesizing minimal cells—those with genes and “…biomolecular machinery necessary for basic life…” – is useful for understanding “core biology.” Minimal Cell Project (MCP) research efforts include a “top down’ reduction of bacterial genomes in vivo and “DNA/RNA/protein/membrane syntheses in vivo [bottoms up].”
Again, the complexity of cellular life makes clear the major hurdles encountered, and we are left with a sense of awe at the miracle of life on Earth and how it is so varied and clever at finding ways to survive, evolving in a wide range of extreme conditions and remote niches.
Author of The Webs of Varok
Nautilus silver award 2013 YA
ForeWord finalist 2012 adult SF
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