Is there Life on Earth? The Search for (extra)-Terrrestrial Life.An idea adapted for U.M. biology classes by C. Mallery, from Carl Sagan's Book
Imagine that you are the science officier on the Starship Voyager and you come across a planetary system in the delta quadrant. The system contains 9 planets, most are dark and dreary in appearance, except for one, which is appears as a pale blue dot in your long range scanners. You wonder if it may hold life... life as on your home world of Vulcan?
Is the pale blue dot's environment static or changing, can it support life as you know it? You would like to find out so you conduct some experimental scans to find out. You will compare your results to the properties of life as you know it on your home world.
Visual scanners take a picture of the planet in reflected sunlight (as the Meteosat image - European Space Agency). At this level of resolultion, there is no visiblesign of life. The scanners do reveal lots of white clouds, a polar ice cap, dark brown continents, and a lot of bluish substance, which covers 2/3's of the surface of the planet.
You take some emitted infared scans
of the planet. The hottest regions are shown in yellow grading to red,
grey, then blue, which are the coolest regions. These confirm water in
the polar ice caps, and enough water vapor in the air to account for the
whitish clouds. A suggestion that the bluish material is liquid water can
Average temperature profiles in Mercator projections reveal the hottest spots to be land masses (compare to NASA satellite photos below, JPL - 1979). Temperatures decline from the hottest spots, the dark browns, to reds, to light blues, to dark blues. The top picture shows the daylight temperature profiles, while at the picture below is the average temperature, during the night. All the hot places in daytime have cooled off.
No temperature difference is seen between day and night for the oceans (red bands across middle of pictures). From this fact we might deduce that these ocean areas are made of LIQUID WATER, a substance remarkable in its ability to hold a constant temperature. The SPECIFIC HEAT of water is the amount of heat energy that must be added to raise the temperature of liquid water, one degree centigrade. It is about 80 calories per gram of water, which is why water is reluctant to change its temperature and makes it a good thermal insulator.
Other infrared spectra reveal that the atmosphere of this planet is about 1/5 oxygen. No other planet in this system has so much oxygen. Where did it all this oxygen come from. U.V. light can break down water into oxygen and hydrogen, but it can not account for the massive amounts seen on this planet. On our science officer's home planet, plants are a life form that can use pigments to capture photons of light, while breaking down water into oxygen and hydrogen. With this much oxygen you expect to find ozone (O3) in the atmosphere. The ozone then absorbs U.V. light, thus protecting the oxygen producing life forms. Pigment profiles might establish that chlorophyll is present like on the home world.
Infrared spectra also show the presence of water vapor, carbon dioxide, and methane all of which absorb the heat that radiates from the planets surface, thereby warming the planet. You've discovered, a Greenhouse effect on this planet, that keeps its water from freezing. The picture to the right, taken in near infrared light, reveals carbon dioxide and water water both absorb light. The picture reflects the conditions in the upper atmosphere (the ground can not be made out), which when compared to the emitted infrared scans above, further suggests a Greenhouse Effect.
The presence of methane and oxygen in the same atmosphere is a key indicator of possible life forms. The laws of basic chemistry say, that in presence of excess O2, methane should be converted entirely into water and CO2. There should be no mathane at all in the atmosphere of this planet, yet alone the 1 ppm (one part per million) levels detected. The only possible explanation is that methane is being injected into the atmosphere as quickly as it is chemically converted by O2. What is the source of the methane? One major alternative is that the source is biological (like on your home world).... as bacteria in bogs, the burning of vegetation, natural gas from oil wells, the cultivation of rice, and bovine flatulence.
* [In an oxygen atmosphere, the presence of methane is a sign of biological life].
Your instruments may also be able detect technology from the pale blue dot (intelligent life?)
Many natural process emit radio waves,
usually by electrons trapped in strong magnetic fields and lightning. But
these radio frequencies have a constant central frequency, plus a modulation
(on/off). These periodic radio signals may mean intelligent life (I Love Lucy). It seems
that some species of life on this planet has achieved radio technology.
The SETI (Search for Extraterrestrial Intelligence) project on your home world may have found finally other intelligent life in the universe?
To search for this intelligent life form, you initiate finer and finer resolution scans with telescopes, hoping to resolve the physical landscape of the pale blue dot. You see mountain ranges, land erosion processes, running rivers and conclude that a geologically active planet is at hand. Your images (as in this METEOSAT picture), while showing significant geological detail, offers no real signs of life.
Telescopic images taken at night reveal compact concentrations of artificial lights in various continental regions. Maybe these are areas where the life forms congregate. The lights are concentrated near coastlines and are sparse in the continental interiors.
At about 100 meters resolution, the larger magnifications (as in Landsat 6 photos) reveals some signs of life, i.e., in this false color image, the black object is a body of water (the Salton Sea in Southern California). The green checkerboard pattern is vegetation - agricultural fields organized in squares and rectangles. The regularity, complexity, and distribution of these vegetational plots would be hard to explain, except by an intelligence, modifying its natural habitat.
Images taken at one meter resolution reveal crisscrossing lines in densely populated areas. As was noted by Carl Sagan in his book, Pale Blue Dot, "long straight lines connect one area to another, and its is easy to see streamlined, multicolored beings, 2 to 3 meters in length, following each other in slow processional order. One stream stops, as another continues at right angles. Periodically the favor is returned. At night they 'emit' two bright lights at their front, so they can see where they are going. Some go into little rectangular dwellings, but most are homeless and sleep on the streets". At Last! You have detected the source of the all the technology, the dominant life form of the pale blue dot. The streets of the cities and the roadways of the countryside are obviously built for their benefit. At a slightly higher magnification you see tiny parasites occasionally enter and exit 'these dominant organisms'. A stationary dominant organism will often start up after it has been infected with a parasite and stop just before a parasite is expelled... Puzzling."
Your expedition to the pale blue dot of a planet is successful. You've characterized its environment. You've probably detected an intelligent life form, that releases oxygen, produces methane, makes geometrical patterns in the land. The dominant species moves around in straight lines, and is infected with smaller parasites.
This planet is worthy of further study, so you insert your space craft into orbit around Earth, with the idea of one day implanting some of your own species' DNA into the life patterns of the dominant organism of this pale blue planet.
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Last Update - 5 July 2000