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Chapter 28: Problem 2

What is meant by "life as we know it"? Why do astrobiologists suspect that extraterrestrial life is likely to be of this form?

Short Answer

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Life as we know it encompasses life forms that undergo growth, reproduction and adaptation in an environment, predominantly consuming energy and possibly involving cells. Astrobiologists suspect extraterrestrial life to share these characteristics because they are derived from Earth's life - the only evidential model of life currently known to us. The existence and conditions of extraterrestrial life, however, still remain unexplored.

Step by step solution

01

Define 'Life as we know it'

Life as we know it refers to the forms of life that we are familiar with on Earth. This largely encompasses beings that are made up of cells, have a metabolism, undergo growth, can reproduce, respond to their environment, and can adapt to their environment over successive generations.
02

Explain why astrobiologists suspect extraterrestrial life to follow Earth's model

Astrobiologists base their theories on the only example of life that they have - life on Earth. They hypothesise that for life to exist it requires certain conditions similar to what is found on the Earth such as water, a source of energy (like the sun), and potentially, though not necessarily, an atmosphere. As Earth's life forms have adapted to utilise these sources and conditions, it is believed that extraterrestrial life might function on similar principles. However, it is still a hypothesis as the exact conditions and existence of life outside Earth remains unconfirmed.

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Most popular questions from this chapter

It has been suggested that extraterrestrial civilizations would choose to communicate at a wavelength of \(21 \mathrm{~cm}\). Hydrogen atoms in interstellar space naturally emit at this wavelength, so astronomers studying the distribution of hydrogen around the Galaxy would already have their radio telescopes tuned to receive extraterrestrial signals. (a) Calculate the frequency of this radiation in megahertz. Is this inside or outside the water hole? (b) Discuss the merits of this suggestion.

Astronomers have proposed using interferometry to make an extremely high- resolution telescope. This proposal involves placing a number of infrared telescopes in space, separating them by thousands of kilometers, and combining the light from the individual telescopes. One design of this kind has an effective diameter of \(6000 \mathrm{~km}\) and uses infrared radiation with a wavelength of \(10 \mathrm{~mm}\). If it is used to observe an Earthlike planet orbiting the star Epsilon Eridani, \(3.22\) parsecs (10.5 light-years) from Earth, what is the size of the smallest detail that this system will be able to resolve on the face of that planet? Give your answer in kilometers.

Mercury, Venus, and the Moon are all considered unlikely places to find life. Suggest why this should be.

The Drake Equation. Access the Active Integrated Media Module "The Drake Equation" in Chapter 28 of the Universe Web site or eBook. (a) For each of the terms in the Drake equation, choose a value that seems reasonable to you. How did you choose these values? Using the module, what do you find for the number of civilizations in our Galaxy? From your calculation, are civilizations common or uncommon in our Galaxy? (b) Using the module, choose a set of values that give \(N=10^{6}\) (a million civilizations). What values did you use? Which of these seem reasonable to you, and why?

Use the Starry Night Enthusiast \({ }^{\text {TM }}\) program to examine the planet Mars. Open the Favourites pane and double-click on Solar System > Mars to view this planet from about \(6800 \mathrm{~km}\) above its surface. (Click on View > Feet to remove the astronaut's spacesuit from the view.) You can zoom in or out on Mars using the buttons in the Zoom section at the right of the toolbar. You can rotate Mars by placing the mouse cursor over the image and moving the mouse while holding down the mouse button. (On a two-button mouse, hold down the left mouse button.) Rotate Mars and zoom in and out to familiarize yourself with the different surface features. Based on what you observe, where on the Martian surface would you choose to land a spacecraft to search for the presence of life? Explain how you made your choice.
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