The start of the semester always gets me thinking about ways to capture student interest in science and biology. Even nonmajors want to know whether life exists on other planets. Mars, of course, is a prime candidate.
I have been searching for resources that might help me combine the “What Is Life?” content with the “Process of Science” content typical of chapter 1 in an introductory textbook. I touched on the first issue in a previous blog post describing an active learning activity helping students articulate the characteristics of life. But combining that topic with current research on Mars life might be a good way to bring in the process of science as well.
The question to present to students is this: Short of sending astronauts to the Red Planet, how could we test the hypothesis that life exists on Mars? Students might begin with the standard list of life’s characteristics: organization, energy use, homeostasis, reproduction/growth/development, and evolution. They could then organize the list from “most likely” to “least likely” to be detectable from Earth.
Students might be surprised to learn how much evidence about Mars we can gather from Earth. For example, the Wikipedia article about life on Mars lists several measurable “habitability factors” including the presence, location, and state of water; the chemical environment; the physical environment; and the availability of an energy source. These characteristics might not tell us much about the organization, reproduction, or evolution of life on Mars, but they do relate directly to energy use and homeostasis. The instruments on the Mars Rovers can collect many additional clues about the climate and geology of the planet.
An important feature of scientific thinking is that our conclusions are only as good as our data, and sometimes the data are not clearcut. For example, this compelling, short BBC video from 2010 says that Earth-based measurements detected plumes of methane on Mars. (The scientist in the documentary relates Mars methane to Earth’s termites in a way that is sure to grab student attention; he does, however, make an error when he calls archaea “bacteria.”) On the other hand, according to this September 2013 article from NASA, the rover Curiosity did not detect methane in the Martian atmosphere. Future Mars explorers may help settle the question. Or they may complicate the science by transferring Earthly microbes to Mars; my colleague Kelly Cowan described this interesting twist in a blog post about protecting the red planet from Earth aliens.
If students are looking for a definitive answer to the question of whether life exists on Mars, this topic will disappoint. But if they are looking to learn more about life and to test the limits of science, this may provide interesting food for thought.
P.S. Since a new semester is about to start, this might be a good time to check out last August’s “My Best Idea for Semester Prep” post.