Extraterrestrial life could be living in the clouds of distant and not-so-distant planets, a new study published online in the journal Astrobiology suggests.
According to a team of researchers at the University of Wisconsin-Madison's Space Science and Engineering Center we may have to think beyond the traditional when hunting for extraterrestrial life. In the study researchers have put forward a case that extraterrestrial life in the form of microbes could be living in the clouds of Venus.
Researchers say that Venus is a planet on which life, if spawned, have had enough time to evolve owing to presence of liquid water on its surface for almost 2 billion years. That's a period that's much longer than is believed to have occurred on Mars.
On Earth, terrestrial microorganisms -- mostly bacteria -- are capable of being swept into the atmosphere, where they have been found alive at altitudes as high as 41 kilometers (25 miles) by scientists using specially equipped balloons, according to study co-author David J. Smith of NASA's Ames Research Center.
There is also a growing catalog of microbes known to inhabit incredibly harsh environments on our planet, including the hot springs of Yellowstone, deep ocean hydrothermal vents, the toxic sludge of polluted areas, and in acidic lakes worldwide.
Researchers note that the cloudy, highly reflective and acidic atmosphere of Venus is composed mostly of carbon dioxide and water droplets containing sulfuric acid.
The habitability of Venus' clouds was first raised in 1967 by noted biophysicist Harold Morowitz and famed astronomer Carl Sagan. Decades later, the planetary scientists David Grinspoon, Mark Bullock and their colleagues expanded on the idea.
Supporting the notion that Venus' atmosphere could be a plausible niche for life, a series of space probes to the planet launched between 1962 and 1978 showed that the temperature and pressure conditions in the lower and middle portions of the Venusian atmosphere -- altitudes between 40 and 60 kilometers (25-27 miles) -- would not preclude microbial life. The surface conditions on the planet, however, are known to be inhospitable, with temperatures soaring above 450 degrees Celsius (860 degrees Fahrenheit).
Spectroscopic observations, particularly in the ultraviolet, show that the dark patches are composed of concentrated sulfuric acid and other unknown light-absorbing particles. Those dark patches have been a mystery since they were first observed by ground-based telescopes nearly a century ago, says one of the researchers involved with the study. They were studied in more detail by subsequent probes to the planet.
The particles that make up the dark patches have almost the same dimensions as some bacteria on Earth, although the instruments that have sampled Venus' atmosphere to date are incapable of distinguishing between materials of an organic or inorganic nature. The patches could be something akin to the algae blooms that occur routinely in the lakes and oceans of Earth, according to the team - only these would need to be sustained in the Venusian atmosphere.