Miller had probed the origin of life by passing electricity through a glass container of organic chemicals to see what came out. Bada found fascinating hints that the origin of life may well be on an Earth-like planet rather than the exception.

　　Kanfman dealt with the question of how many such planets are likely to exist.

　　Unfortunately, the most habitable planet found is widely believed not to exist life at all. Butler and Vogt appropriately noted that their find would have to be confirmed by others before it could be considered rock solid. The same applies to evidence of alien life. In no case was any real E. T.

　　proved to exist. The twin Viking probes landed on Mars and performed on-site tests of the soil, looking for life. Most came back negatively, but one, designed by NASA scientist Gilbert Levin, showed suspicious activity.

　　Research has proved what’s true today often is overturned tomorrow, and what’s rejected today may be accepted tomorrow. Even if you limit your thinking to life, the Milky Way is likely teeming with life. Researchers are considering the possibility of planets dominated by a sulfur cycle rather than the carbon cycle. That would be life as we don’t know it. Kaufman’s claim “scientists will determine life exists elsewhere in the universe” may actually be an understatement.

　　1. Why do scientists do research on astrobiology?

　　A. Because there’s no evidence that life exists or ever existed beyond the earth.

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