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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

Expert verified
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

Search the World Wide Web for information about the Mars Express orbiter and the Spirit and Opportunity rovers. What discoveries have these missions made about water on Mars? Have they found any evidence that liquid water has existed on Mars in the recent past? Describe the evidence, if any.

Use the Starry Night Enthusiast \({ }^{\text {TM }}\) program to view the Earth as it might be seen by a visiting spacecraft. First, select Viewing Location ... in the Options menu and set the viewing location to your city or town from the list of cities provided or click on the Map tab in the Viewing Location pane and use the mouse to click on your approximate position on the world map. Then click the Set Location button. Set the local time to 12:00:00 P.M. (noon). To see the Earth from space, use the up and down elevation buttons on the toolbar to raise yourself above the surface until you can see the entire Earth. You can use the scrollbars (select View > Show Scrollbars) on the right side and bottom of the window to center the Earth in your view. The Earth can be rotated to allow you to see different locations by clicking and moving the mouse while its icon, a fourway arrow, is over the Earth's image. (a) Describe any features you see that suggest life could exist on Earth. Explain your reasoning. (b) Using the controls at the right-hand end of the toolbar, zoom in to show more detail around your city or town. The amount of detail is comparable to the view from a spacecraft a few million kilometers away. Can you see any evidence that life does exist on Earth? (c) From a distance of a few million kilometers, are there any measurements that a spacecraft could carry out to prove that life exists on Earth? Explain your reasoning.

Like other popular media, the World Wide Web is full of claims of the existence of "extraterrestrial intelligence"namely, UFO sightings and alien abductions. (a) Choose a Web site of this kind and analyze its content using the idea of Occam's razor, the principle that if there is more than one viable explanation for a phenomenon, one should choose the simplest explanation that fits all the observed facts. (b) Read what a skeptical Web site has to say about UFO sightings. A good example is the Web site of the Committee for the Scientific Investigation of Claims of the Paranormal, or CSICOP. After considering what you have read on both sides of the UFO debate, discuss your opinions about whether aliens really have landed on Earth. NM2e,

Any living creatures in the subsurface ocean of Europa would have to survive without sunlight. Instead, they might obtain energy from Europa's inner heat. Search the World Wide Web for information about "black smokers," which are associated with high-temperature vents at the bottom of Earth's oceans. What kind of life is found around black smokers? How do these life-forms differ from the more familiar organisms found in the upper levels of the ocean?

Why are most searches for extraterrestrial intelligence made using radio telescopes? Why are most of these carried out at frequencies between \(10^{3} \mathrm{MHz}\) and \(10^{4} \mathrm{MHz}\) ?
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