<p> Name: ______Date: ______Pd: ____</p><p>Excerpts from: Are We All Aliens? The New Case for Panspermia By Robert Roy Britt 30 October 2000 http://www.space.com/searchforlife/aliens_all_001027-2.html</p><p>Nestled safely inside the belly of a comet orbiting some unknown star, a microscopic alien sits dormant. Somewhere in this vast universe -- perhaps a place like Earth -- a greater destiny awaits the microbe. A place to flourish, become a nematode or a rose or a teenager. Over time, gravity performs a few plausible, but not routine tricks, and the comet is ejected from its stellar orbit like a rock from a slingshot. For more than 100 million years it slips silently across the inky vastness of interstellar space. A few giant gaseous planets whiz by, their bulks tugging at the comet, altering its course slightly. Ahead now, growing larger, looms a gorgeous blue and brown marble. Water and land. Maybe some air. Then with the force only the cosmos can summon, the comet slams into the third rock from a mid-sized, moderately powerful star. The alien microbe survives, emerges from its protective shell and spreads like the dickens. Thus began life on Earth, 3.8 billion years ago. Or so goes one aspect of a theory called panspermia, which holds that the stuff of life is everywhere and that we humans owe our genesis and evolution to a continual rain of foreign microbes. It means, simply, that we might all be aliens. It's an idea that has been around [a long time], but which still struggles to gain strong support among most scientists. But two recent discoveries are breathing new life into the theory. One study, reported in the October 27 issue of the journal Science, shows that a space rock could successfully transport life between planets. Another group of researchers, reporting in the October 19 issue of Nature, claims to have found and revived bacteria on Earth that were dormant, in the form of spores, hiding in New Mexican salt crystals for 250 million years. Scientists called the implications of this second discovery profound, suggesting that if further study bears out the findings, it could mean bacterial spores are nearly immortal. "Until recently, panspermia was not even regarded as a scientific hypothesis," says Chandra Wickramasinghe, the concept's leading proponent. "Now that has changed."</p><p>Agreement, but still caution While the prevailing theory holds that life arose spontaneously out of a terrestrial, chemical soup, panspermia's defenders argue that such a miracle could happen almost anywhere. This means we could have microbial ancestors, or even more evolved cousins, in unexplored corners of the cosmos. Panspermia: Its own origins and evolution The idea that the seeds of life are ubiquitous throughout the cosmos goes back to Anaxagoras, a Greek philosopher. In the 1800s, French chemist Louis Pasteur proposed that spontaneous generation of life could not have occurred on Earth. British physicist Lord Kelvin and others jumped on Pasteur's bandwagon and suggested that life might have come from space. Just two leading researchers carry the bulk of the panspermia torch. The renowned Sir Fred Hoyle, known for his studies of star structure and the origin of the chemical elements in stars, has worked with Chandra Wickramasinghe over the past three decades to pioneer the modern theory of panspermia. In the 1970s, Wickramasinghe and Hoyle found what they say are traces of life in the dust around distant stars. The duo then broadened the panspermia theory, arguing that a continual rain of life-altering stuff from space -- including germs that arrive in cycles related to solar activity -- has affected the course of evolution. The seeds, they say, are still coming. Support for parts of panspermia Other researchers agree that both space rocks and comet dust might in fact harbor organic matter. But how these ingredients for life might travel from one star to another is hotly disputed. Name: ______Date: ______Pd: ____</p><p>Even as doubters are beginning to give panspermia advocates a little respect, most say the likeliest transfers of life would occur between planets. "That bacteria, or at least their spores, can survive for such staggering amounts of time makes their transport from planet to planet on meteorites possible," said Matthew Genge, a meteoritic researcher at the London Natural History Museum. "Bacterial spores in their very own kind of suspended animation could perhaps survive the millions of years it takes for rocks to travel from planet to planet." But Genge, along with other scientists, cautioned that the 250-million-year-old bacteria found in New Mexican salt crystals are not conclusive. There is a chance the samples were contaminated with more modern bacteria, and follow-up studies need to be done. "Not all microbes in interstellar space would survive of course," Wickramasinghe said. "But the survival of even a minute fraction of microbes leaving one solar system and reaching the next site of planet formation would be enough for panspermia to be overwhelmingly more probable than starting life from scratch in a new location." So despite all the new and important discoveries, we still don't know how or where life began. But the search for it has gotten a little more interesting, now that we know we might all be aliens.</p><p>Answer the questions below. 1. What about the panspermia hypothesis supports the title “Are We All Aliens?”</p><p>2. According to the panspermia hypothesis, how might life have arrived planet Earth?</p><p>3. What recent discoveries are said to support this hypothesis?</p><p>4. Who was the first to propose this idea?</p><p>5. Describe Wichramasinghe and Hoyle’s contributions to the panspermia hypothesis.</p>