Presentation on theme: "Does life exist elsewhere in the Universe?"— Presentation transcript:
1 Does life exist elsewhere in the Universe? By Imtiaz Hanif
2 What is life?Life is notoriously hard to define. You have to think carefully about what you mean. If you consider life a system that's self-organizing and self-reproducing, then stars are alive. In 1994, a NASA panel defined life as a "chemical system capable of Darwinian evolution." Life doesn't just sit there; it does something. And that "something" in large part, is metabolism; the process of taking in materials, extracting energy from them to fuel growth and other activities, and then expelling the waste. Motion thus appears to be a hallmark of life.
3 Where did life originate? The significance of hydrothermal systems in life's history appears in the "tree of life," constructed recently from genetic sequences in RNA molecules, which carry forward genetic information. This tree arises from differences in RNA sequences common to all of Earth's living organisms. Organisms evolving little since their separation from their last common ancestor have similar RNA base sequences.To create the building blocks from which life can assemble itself, one needs access to biogenic elements. On Earth, these elements include carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus.
4 Cont’d...On Earth today, nearly all of life's energy comes from the sun, through photosynthesis. Yet chemical energy sources suffice and would be more readily available for early life.
5 How life on Earth Started The planet was being rained on constantly by enormous meteorites that vaporized when they hit the ocean and created dust clouds that blocked out the sun.The atmosphere was a thick, smoky blanket of carbon dioxide.It is believed that life did not begin on Earth's surface, but far below on the ocean's floor.Protection from the sun's ultraviolet rays, a constant temperature, and a chemical makeup conducive to the creation of life.
6 Possibilities for life in the solar system. The planet closest to the Sun, Mercury, is too hot.The next out, Venus, while it is very Earth-like in size and shape, has an average temperature of 475 degrees C (still too hot), and a lack of life giving water.Beyond that the planets, with the exception of the last, Pluto, are gas giants (Jupiter, Saturn, Uranus and Neptune)
7 Life on Mars.Mars today is not very hospitable. Daily average temperatures rarely rise much above 220 Kelvin, some 53 Kelvin below water's freezing point. Despite this drawback, abundant evidence suggests that liquid water has existed on Mars's surface in the past and probably is present within its crust today.Volcanism has supplied heat from the earliest epochs to the recent past, as have impact events. Additional energy to sustain life can come from the weathering of volcanic rocks. Oxidation of iron within basalt, for example, releases energy that organisms can use.Although the history of Mars's atmosphere is obscure, the atmosphere may have been denser during the earliest epochs, 3.5 to 4.0 billion years ago. Correspondingly, a denser atmosphere could have yielded a strong greenhouse effect, which would have warmed the planet enough to permit liquid water to remain stable.
8 Cont’d..An inventory of energy available on Mars suggests that enough is present to support life. Whether photosynthesis evolved, and thereby allowed life to move into other ecological niches, remains uncertain.
9 Tiny tubular shape resembling fossilized bacteria. Sample ALH84001.Landed in Antarctica.In 1984 it was picked up by scientists who identified it's place of origin by comparing bubbles trapped in the rock with the known mixture of gases on Mars.
10 Life on Europa.The largest of Jupiter's satellites, Europa is a little bit smaller than our moon, and its surface is covered with nearly pure ice. Yet Europa's interior may be less frigid, warmed by a combination of radioactive decay and tidal heating, which could raise the temperature above the melting point of ice at relatively shallow depths.Europa has all the ingredients from which to spark life. Of course, less chemical energy is likely to exist on Europa than Mars, so we should not expect to see an abundance of life, if any.
11 UFOs and Aliens Air Force term "Unidentified Flying Object“ Three Kinds of EncountersEncounters of the first kindEncounters of the second kindClose encounters of the third kindAlien abductions
12 ReferencesAchenbach, Joel. Essick, Peter. Life Beyond Earth. National Geographic; Jan2000, Vol. 197 Issue 1, p24. from: Gibbons, W. (July 23, 2006) HOW DID LIFE START ON EARTH? Retrieved April. 21, 2009, from: Jakosky, Bruce M. Searching for Life in Our Solar System. Scientific American Presents; 1998, p16-2. from: Nadis, Steve. Does life really need water? Astronomy; Nov2006, Vol. 34 Issue 11, p from: The Museum Of Unnatural Mystery. Retrieved April. 21, 2009, from: