The Associated Press reported on February 14, 1997 that scientists now believe life might be found beneath the surface of planets that seem inhospitable on the surface. The new ideas were discussed in Seattle, Washington at the annual meeting of the American Association for the Advancement of Science.
Mars is one of several places in our own solar system that could harbor underground life. John Delaney of the University of Washington speculated that Mars could have sub-surface geothermal springs and pools, similar to those in Wyoming's Yellowstone Park, that contain microbial lifeforms.
Sentiment is also growing in favor of possible life on Jupiter's moon Europa, where a planetary icecap may cover and protect a liquid ocean. There is even discussion of possible life on Venus, where surface temperatures may reach 800 degrees fahrenheit.
NASA's announcement last August of a possible microbe-bearing meteorite from Mars has set off a scientific ferment that shows no sign of slowing down. Discussion of life on other worlds is not only acceptable now, it's hot.
And it is dawning on many scientists that earth's version of air-breathing, water-drinking, sun-loving lifeforms might not be the only shape life takes -- perhaps not even the most common pattern.
Thomas Gold, an astronomer from Cornell University, has suggested that "we are the anomaly, and the stuff down there [underground] is what is common." Gold, a colleague of the late Carl Sagan, started talking about the possibility of deep subterranean life long before it was fashionable, but has seen his ideas gain wide acceptance in recent months.
Even twenty years ago, however, data was accumulating that suggested the possibility of extraterrestrial life underground. The Voyager spacecraft found that volcanic activity is
much more common in the solar system than had been supposed, meaning that even on frigidly cold, dark planets there could be pockets of warmth near the surface. Meanwhile, oceanographers discovered primitive microbes living at extreme depths at the sea floor around hydrothermal vents. These organisms live in a chemically alien environment, under crushing pressure, and without the slightest trace of sunlight -- conditions that might well be found on other planets.
These observations sat side by side without coming together until researchers announced the Martian meteorite in August, 1996. Then, suddenly, unthinkable things became intriguing.
Speaking of the meteorite researchers, Delaney said, "They have opened a valid dialogue about life on other planets. For a long time that's not something that respectable scientists did."
A big factor fueling the new debate on extraterrestrial life is the growing awareness that water is far more common and available on other planets than previously supposed. Most of the water on Mars is probably locked up in permafrosts or deep subsurface deposits, scientists now speculate, but if the total estimated amount of water on Mars could be spread evenly over a smooth surface, it could cover the whole planet to a depth of 600 feet.
On earth, scientists find that almost anywhere water can penetrate, life can be found. Life has recently been found -- in the form of primitive bacteria -- inside solid rock a mile below the earth's surface. Scientists also find that bacteria thrive wherever a volcanic vent opens on the ocean floor. These bacteria are so primitive that they may be among the oldest lifeforms on earth, suggesting that these deep vents are the kind of place life actually begins. Living where they do, such bacteria are also impervious to virtually all changes that affect the earth's surface, including rare mass-extinction events such as asteroid strikes.
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