Goldilocks Principle and Manned Space Travel

The classic fairytale 'Goldilocks and the Three Bears' tells the story of a young child who wanders into a strange house in the woods. She finds one bowl of porridge too hot, another too cold and the third 'just right.'

Astronomers sometimes apply the tale to a planet's ability to sustain life as we know it. In our own star system, Venus is too hot and Mars is too cold for us -- but Earth is just right. Broadly speaking, the Goldilocks principle applies to any situation where only a particular range of conditions is agreeable.


On earth, two elements, nitrogen (N2) and oxygen (O2), make up almost 99% of the volume of clean, dry air. Most of the remaining 1% is accounted for by the inert gaseous element, argon (Ar). Argon and the tiny percentage of remaining gases are referred to as trace gases. Certain trace atmospheric gases help to heat up our planet because they appear transparent to incoming visible (shortwave) light but act as a barrier to outgoing infrared (longwave) radiation. These special trace gases are often referred to as "greenhouse gases" because a scientist in the early 19th century suggested that they function much like the glass plates found on a greenhouse used for growing plants.

The earth's atmosphere is composed of gases (for example, CO2 and CH4) of just the right types and in just the right amounts to warm the earth to temperatures suitable for life. The effect of the atmosphere to trap heat is the true "Greenhouse effect."  

We can evaluate the effect of greenhouse gases by comparing Earth with its nearest planetary neighbors, Venus and Mars. These planets either have too much greenhouse effect or too little to be able to sustain life as we know it. The differences between the three planets have been termed the "Goldilocks Principle" (Venus is too hot, Mars is too cold, but Earth is just right).

Mars and Venus have essentially the same types and percentages of gases in their atmosphere. However, they have very different atmospheric densities.
has an extremely dense atmosphere, so the concentration of is responsible for a "runaway"
      greenhouse effect and a very high surface temperature.
     Mars has almost no atmosphere; therefore the amount of is not sufficient to supply a warming
     effect and the surface temperatures of Mars are very low.

Earth has a very different type of atmosphere. Our atmosphere has much less CO2 than Venus or Mars and our atmospheric pressure is close to midway between the two (1/90th that of Venus and 100 times that of Mars).

Many scientists believe that the composition of our atmosphere is due to the presence of life.
Life acts to keep Earth's atmosphere in a dynamic balance.

In other words, if life were to completely disappear, eventually our atmospheric composition could come to closely resemble Mars or Venus. Only with life continually producing oxygen through photosynthesis and removing and re-circulating does Earth's atmosphere remain fairly stable.

Let's Go to MARS!
Life in Space

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Why wear Spacesuits?

Space travelers wear a spacesuit in order to bring along elements of Earth’s environment needed for survival: oxygen, air pressure, moderate temperatures, and protection against the Sun’s rays. On earth, our atmosphere absorbs much of the sun;s harmful rays. In space and on planets the thin atmosphere provides little protection for astronauts. 
The vacuum of space is another harsh environmental condition, causing fluids to boil due to lack of air pressure. Bubbles form in the bloodstream and tissue, capillaries and other fragile tissues would rupture. Lack of oxygen would render the unfortunate individual unconscious in 15 seconds and permanent brain damage in as little as 4 minutes, followed shortly thereafter death.
Key Question
What function does a spacesuit need to have for a mission to mars?

Spacesuit Criteria
1. Function on Mars.
2. Have features needed to accommodate human body functions.
3. Take into account Mission Control needs.
4. Allow astronauts to perform mission tasks. (climb, repell, dig, collecting rocks ,ice, etc.)
Q & A
Why do humans need to wear spacesuits?
How is movement in space different from movement on Earth?
What does a spacesuit have to include?
A system for breathing, air pressure, temperature control, walking, identification, food storage…can you think of any more…
How can a spacesuit make work harder to complete?
Bulky because of the many systems and stiff due to air pressure.

Why don’t astronauts need to wear a spacesuit in a spacecraft?
How does a spacesuit worn in space differ from those needed for Mars?
Mars needs suits that function below freezing, with adaptations for fine dust particles that could affect visibility and leak into suit joints. Both need oxygen.
Mission Control
Mission Control plays a critical role in keeping astronauts safe and helping them complete tasks during extravehicular activities (EVA’s) or spacewalks. Spacesuits need to have special features so that Mission Control can be sure the suits are functioning well. They also need to communicate with and identify the astronauts.




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