Fri, May 09, 2014 page9

• Planets similar to Earth should be found in a decade

  There are a multiplicity of worlds orbiting stars like ours, which could put our own planet into context and provide vital data

  • By Caleb Scharf
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  We have always lived on a changing planet, but many of today’s variations in climatic and ecological states are taking place exceptionally fast and are directly attributable to our behavior. Slowing the rate of alteration is the only rational course of action, given the potential outcomes, but we also need to examine our responses closely, or risk repeating our shortsighted behavior.

  Unexpectedly, the search for life elsewhere in the universe may provide a critical new perspective.

  Our technologically advanced civilization — replete with remarkable tools and notable headaches — owes everything to a tapestry of cosmic and planetary history. Consider, for example, oil, gas and coal. These substances comprise a complex package of carbon chemistry, produced by biology and geophysics operating within a deep rhythm of variation and evolution originating far from our own epoch. The minerals and rare-earth elements that we exploit to build ingenious devices — extending our bodies and minds — are also a part of this rhythm, and are accessible only because of a great chain of circumstances, from planetary origins to plate tectonics and asteroid impacts.

  Our trajectory as a species is hardwired to this 4 billion-year-old bio-geo-chemical system that has profoundly worked and reworked the planetary environment, all the way from bacteria to city planners, atmospheric oxygen to paper mills.

  In addition to our own genes, each of us carries the genes of tens of trillions of microbial passengers. These tiny organisms harbor codes for metabolic processes that have been preserved across eons — the same processes responsible for shaping the world. It is a plausible blueprint for successful life anywhere, even if the biochemical details differ.

  Our daily business usually ignores this existential backdrop. The struggle to mold our future, to stave off the humanitarian disasters of war, disease and starvation leaves little room to be philosophical about our place on this crumb of cosmic dust. However, many scientists, including me, have a sense that the universe might be about to reach in and give us a metaphorical slap in the face.

  For the past few decades, the modern scientific endeavor known as astrobiology has been seeking to determine whether all of this — life, death and evolution — has happened elsewhere in the cosmos. Humans have long asked this question, but the evidence — the raw data — was lacking.

  Now, astronomers have discovered a remarkable abundance of planets orbiting other stars. The numbers tell us that 15 percent to 20 percent of sun-like stars harbor worlds similar in size to the Earth, orbiting stellar parents at distances implying that their surfaces might be temperate.

  We have not found the nearest such world yet, but statistically it should be within about 15 light years of us — a stone’s throw in cosmic terms. There is an excellent chance that we will find it and its brethren within a decade, and search for signs of an alien biosphere in these worlds’ atmospheric compositions or climates.

  In the Solar System, NASA’s Curiosity rover has discovered what may be organic carbon in the fossil mud of an ancient Martian lakebed. Europa, Jupiter’s icy moon, has been spotted spewing water into space from a hidden ocean that could hold twice the volume of all of Earth’s oceans. Serendipity is providing us with access to an abyssal realm that could conceivably harbor life. We just have to go smell the salty spray.

  Even finding nothing in such places is important, because these new data have predictive power, narrowing the field of planets, or moons, that might harbor life. Nature has the critical experimental data that we need to finally place Earth in context, within a zoo of worlds emerging from ice ages, worlds descending into greenhouse hells, young worlds, old worlds, barren worlds and possibly worlds teeming with life. That means that we will have new data to steer decisions about planetary stewardship.

  In other words, the cosmic sprawl can help us disentangle the complex terrestrial systems and histories of which we are a part. This is not a frivolous exercise. On the contrary, it could be the key to overcoming our scientific ignorance. We might guess the general consequences of global warming in the next couple of decades, but the details remain hard to predict, as does the distant future.

  Biological networks change, chemical balances change, species go extinct, ecosystems unravel, and new ones emerge. Cosmic context would go a long way in sorting this out.

  For many people, the idea of spending time and resources on such otherworldly pursuits is difficult to swallow, but if we are to sustain our species into the distant future, we need to make big decisions correctly.

  It is time to take the long view seriously, because we have tried the short view, and it has not worked.

  Caleb Scharf is director of astrobiology at Columbia University.

  Copyright: Project Syndicate

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