Life on Earth and Elsewhere
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Larger and jumbo images;
Northern Americas (jumbo) and
Western Pacific (jumbo); and
cloudless Africa-Eurasia (jumbo)
and Southern Americas (jumbo).
The development of life on Earth
is no longer thought to have been
an improbable event, but one
which may be common under
similar environmental conditions
elsewhere, around other stars as
well as in our own Solar System.
Life in the Solar System and Beyond
Today, biologists no longer think that the development of life on Earth was an improbable event, one unlikely to have occurred twice in the galaxy or even the entire universe. Some now think that carbon-based life like our own is bound to arise on any Earth-like planet, and that Earth-type bacteria can even spread through space via asteroidal and cometary impact ejecta to colonize accommodating habitats anywhere. Hence, the universe could be teeming with life, even if it is likely to be mostly microbial in size (as it is on Earth itself, where single-celled bacteria have been found miles deep below as well as within and on surface rock [and in sub-surface rock down to the gabbroic layer just above the molten mantle], within and beneath the oceans and polar ice, floating in the air, and within as well as on Homo sapiens sapiens). On June 1, 2011, moreover, a team of scientists reported that some species of nematode, very small roundworms that are one of the hardiest and most successful, multi-cellular organisms on Earth, apparently have adapted to living 0.9 to 3.6 kilometers (0.6 to 2.2 miles) below Earth's surface in very hot water (reaching 43 °C or 109 °F) flowing between fractured rocks by eating bacteria, which suggests that similarly small but tough, multi-cellular life may have adapted to living on the subsurface of other planets, even if their planetary surfaces are no longer habitable (Borgonie et al, Nature, June 1, 2011; Ed Yong, Discover, June 1, 2011; Marc Kaufman, Washington Post, June 1, 2011; and Zena Iovino, New Scientist, June 2, 2011).
© Wim van Egmond
(used with permission)
Photo from Ciliates.
Earth-type lifeforms found
elsewhere will likely be most
commonly represented by
microbes (as they are on
Earth), such as these two
Euplotes (left) and Stylonychia,
that move with hairlike cilia.
A key test of this hypothesis would be to ascertain whether carbon-based life ever arose in Earth-like habitats that may have once existed, or still persist, elsewhere in the Solar System -- on Mars, on Venus, and in other planetary bodies (including sub-ice oceans on Europa and other large moons of the outer gas giants) -- as well as around other stars. In 2007, some interesting papers were also published about the likely visual wavelengths or colors of light that may be used for photosynthesis by "alien plants" living under stars bluer or redder than our own Sun. Elsewhere, however, life may take on forms and rely on biochemical processes that are not yet familiar.
For more information, see:
More on lithopanspermia; surviving ejection from Mars without sporulation; and experimental updates from: Mark Anderson, New Scientist, March 31, 2008; and Anil Ananthaswamy, New Scientist, January 11, 2002. See also: Horneck et al, 2008; Stöffler et al, 2006; and Adams and Spergel, 2005.
Try the NASA Astrobiology Institute (NAI).
Belarusian - You can "read "Life on Earth and Elsewhere" in the Belarusian language due to the generous translation and web hosting efforts of Paul Bukhovko.
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