Discussion Homework

Discussion Topic

Unit 1: Is there life off Earth?

Read and provide your opinion on this topic: Should tax dollars be spent to search for life on other planets?

Is There Life Off Earth?

Life as we define it on Earth is based on the following characteristics:

-Reproduction. Living systems are able to reproduce on their own.

-Growth. After a living system is “born,” it grows.

-Metabolism. Living systems share a complex chemistry that includes nutrient cycling (taking in food and giving off waste), energy production, protein synthesis, and DNA replication.

Macroscopic living systems such as animals and plants have so far not been found anywhere off our planet. But it is possible that there are systems off Earth that possess the cellularity, chemical organization, and complexity we equate with being “alive.” Traces of once-living microbes (fossils) have been found on Mars. Also, a meteorite found in Antarctica and thought to be from Mars contains some organic waste products and minerals very similar to those found where dead microorganisms on Earth have been collected. Finally, scientists have found microorganisms living in the Atacama Desert in Chile, which was once thought to be an inhospitable, sterile environment reminiscent of Mars. The microbes apparently are capable of long-term dormancy. When environmental conditions become favorable (rain once every decade), it is thought that these microbes then flourish.