Why do we doubt that life exists in space?
In the 1950s, British astronomer Fred Hoyle pointed out that, when Earth was created, its elements were mixed in the right proportions for life to emerge. Living organisms have almost equal numbers of carbon and oxygen atoms. Too little oxygen would have deprived the Earth of rock and soil; too much would have denied existence to the basic molecules in living organisms.
One by one, probes far into space have revealed conditions so different from anything on Earth that it seems that life as we know it is unlikely anywhere else in our solar system. Our galaxy has 100 000 million stars and other bodies. So far we have tested comparatively few planets and their satellites, but many scientists say that the possibility of life exists on only three of them.
In 1976, Viking 1 and Viking 2 examined the soil on Mars for signs of microscopic life. None was found, but nobody is yet bold enough to close the casebook. Mars has many different environments. One of them could have something resembling our bacteria.
Europa, a moon ofJupiter, and Titan, the largest satellite of Saturn, are other possibilities. Space probes show that beneath Europa’s outer shell is an enormous well of liquid, which may be water. Europa has no oxygen, and none of the Sun’s warmth pierces its shell. However, some dark and oxygen less places on Earth’s seabed hold primitive forms of life. Similar life could perhaps exist in Europa’s darkest caverns.
Titan’s atmosphere consists of nitrogen and methane. Its surface resembles Earth’s landmasses surrounded by oceans. The oceans aren’t water, but they may be a kind of petroleum, formed by weak sunlight and volcanic heat acting on methane. Scientists are reluctant to say that those oceans cannot support life.
Despite all these doubts, a $ 100-million, ten year program began in October 1992 to search for signals from other civilisations. The quest, by the United States’ National Aeronautics and Space Administration (NASA), is called SETI, the search for extra terrestrial intelligence.
On an intensive scale, it is in two parts: one targets 1000 specific stars; the other scans vast regions of the sky. The world’s largest radio telescope at Arecibo in Puerto Rico and others at Greenbank, West Virginia, and Goldstone in California’s Mojave Desert explore the northern skies. Australia’s Parkes radio telescope surveys the south. Results go to a computer so powerful that it can make 1000 million tests every second to sift messages sent possibly by an alien civilisation from signals occurring naturally in space.
What do researchers expect to find? With luck, a simple (but alien) message indicating, ‘We are here ... we are here.’
If the quest yields nothing, it will confirm what some already believe that through a remarkable combination of events Earth alone received all the necessities of life. That will provide another good reason to protect it. If we ruin our planet, we’ll have nowhere else to go.
One by one, probes far into space have revealed conditions so different from anything on Earth that it seems that life as we know it is unlikely anywhere else in our solar system. Our galaxy has 100 000 million stars and other bodies. So far we have tested comparatively few planets and their satellites, but many scientists say that the possibility of life exists on only three of them.
In 1976, Viking 1 and Viking 2 examined the soil on Mars for signs of microscopic life. None was found, but nobody is yet bold enough to close the casebook. Mars has many different environments. One of them could have something resembling our bacteria.
Europa, a moon ofJupiter, and Titan, the largest satellite of Saturn, are other possibilities. Space probes show that beneath Europa’s outer shell is an enormous well of liquid, which may be water. Europa has no oxygen, and none of the Sun’s warmth pierces its shell. However, some dark and oxygen less places on Earth’s seabed hold primitive forms of life. Similar life could perhaps exist in Europa’s darkest caverns.
Titan’s atmosphere consists of nitrogen and methane. Its surface resembles Earth’s landmasses surrounded by oceans. The oceans aren’t water, but they may be a kind of petroleum, formed by weak sunlight and volcanic heat acting on methane. Scientists are reluctant to say that those oceans cannot support life.
Despite all these doubts, a $ 100-million, ten year program began in October 1992 to search for signals from other civilisations. The quest, by the United States’ National Aeronautics and Space Administration (NASA), is called SETI, the search for extra terrestrial intelligence.
On an intensive scale, it is in two parts: one targets 1000 specific stars; the other scans vast regions of the sky. The world’s largest radio telescope at Arecibo in Puerto Rico and others at Greenbank, West Virginia, and Goldstone in California’s Mojave Desert explore the northern skies. Australia’s Parkes radio telescope surveys the south. Results go to a computer so powerful that it can make 1000 million tests every second to sift messages sent possibly by an alien civilisation from signals occurring naturally in space.
What do researchers expect to find? With luck, a simple (but alien) message indicating, ‘We are here ... we are here.’
If the quest yields nothing, it will confirm what some already believe that through a remarkable combination of events Earth alone received all the necessities of life. That will provide another good reason to protect it. If we ruin our planet, we’ll have nowhere else to go.
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