Lecture 1.2: Searching for Life

What is the current objective evolution of NASA's Mars Exploration Program (MEP)?

NASA's Mars Exploration Program has evolved its objectives from: "Follow the Water" -> "Explore Habitability" -> "Seek Signs of Life"

Define Organism.

Any living entity composed of one or more cells

What is a Unicellular organism?

A free-living organism made of a single cell

What is a Multicellular organism?

Any organism composed of more than one cell

What did Percival Lowell believe about Mars, and what was the outcome of scientific observation regarding his beliefs?

Percival Lowell believed there existed a civilization on Mars and interpreted surface features as "canals"

Detailed imaging from landings by spacecraft, have shown no obvious organisms on Mars, disproving Lowell's theory

What fundamental principle of modern science did Richard Feynman articulate regarding theories and experiments?

If it doesn't agree with experiment, it's wrong

If scientists are searching for life on Mars, what specific kind of life are they primarily looking for evidence of?

Microbial life

Define Microbe (or microorganism).

Any organism too small to see with the naked eye (most, but not all, microbes are unicellular)

What are the two major types of microbes on Earth, and what are key features of Eukaryotes?

2 major types: Prokaryotes and Eukaryotes (they have a cytoskeletons and organelles)

Define Cytoskeleton.

Network of protein fibers within a cell

Define Organelles.

Identifiable membrane-bound structures in cells that perform a particular function

What is the significance of the Alan Hills 84001 (ALH84001) meteorite in the search for Martian life?

Martian meteorite containing objects that some NASA scientists hypothesize could be fossil microbes from Mars because they resemble Earth microbes

Define Scientific Hypothesis.

A testable statement that explains a phenomenon or a set of observations

What is the "central tenet of scientific thought" regarding hypotheses?

All hypotheses must be tested and discarded

Are "theory" and "hypothesis" the same thing?

No

Are theories highly speculative?

No

Does a tested hypothesis become a theory or a natural law?

No

What is the goal of science?

The goal of science is to produce correct/consistent theories

Define Scientific Theory

A well-substantiated explanation of some aspect of the natural world that can incorporate facts, [natural] laws, inferences and tested hypotheses

List examples of successful scientific theories

Theory of universal gravitation
Theory of plate tectonics
Theory of natural selection
Theories of relativity
Quantum theories