Powering a Planet: Energy Sources for Life Quiz

If gravity from a giant planet pulls on a nearby moon, it creates internal friction and heat; if this heat melts ice into oceans, then a moon can be habitable even if it is at a massive distance from the star.

If life uses energy, it leaves clues; if it warms a planet, produces waste gases, reflects specific light patterns, or changes the surface appearance as it grows, then these are all detectable signs.

If a star produces energy by squeezing hydrogen atoms together to form helium, and if that process is called nuclear fusion, then the Sun is a fusion reactor.

If humans cannot make their own food from light or chemicals, they must consume other organisms; if they break down the chemical bonds in that food using oxygen, then they are using chemical energy (respiration).

If energy needs to move through a cell to be used, and if water is the universal solvent that allows molecules to flow and react, then the distance that keeps water liquid is vital for energy use.

If chemicals naturally react until they are stable (equilibrium), and if we see unstable gases like oxygen and methane together, then an active energy source (life) must be constantly producing them.

If life needs energy and water, then volcanic springs, deep-ocean vents, and hidden oceans provide heat and chemicals; if comets have organic chemistry and heat when near a sun, they are also targets. The Moon lacks these.

If life needs a standard way to move energy around inside a cell, and if Adenosine Triphosphate is the universal molecule used for this task, then life creates ATP as its primary "currency."

If light spreads out over the surface of a sphere (4 * pi * r^2), and if the distance (r) doubles, then the denominator is 2^2; if the denominator is 4, then the light intensity becomes 1/4 of the original.

If some specialized bacteria can use light when it is available but switch to eating chemicals when it is dark (facultative organisms), then it is possible for an organism to utilize both energy sources.

If life requires a way to power biological reactions, and if stars provide radiation while certain molecules store potential in their bonds, then sunlight and chemical energy are the two main ways life gets fuel.

If life is diverse, it has evolved to tap into many fuels; if some microbes eat sugar, others "eat" light, and some even process minerals like iron or sulfur, then all these are valid biological energy sources.

If photosynthesis is defined by the use of "photo" (light), and if an organism uses "chemo" (chemicals) to drive the same result of making energy, then the process is called chemosynthesis.

If Earth has a clear atmosphere and sits relatively close to the Sun, then it receives a massive, constant flow of solar radiation; if this is the most abundant fuel available on the surface, then it is the primary source used.

If deep-sea vent ecosystems contain complex communities of worms, crabs, and fish powered entirely by bacteria eating chemicals, then chemical energy is fully capable of supporting a diverse food web without any light.

If photosynthesis requires a minimum amount of light intensity to trigger chemical changes, and if light intensity drops as 1/d^2, then there is a specific distance beyond which light is too faint to support plant-like life.

If a moon is too far from a star to get light, it needs internal heat; if gravity from a planet squeezes the moon or if chemicals and radiation exist in its core, then those can provide the energy needed for life.

If an organism produces its own food by capturing energy from its environment, and if light is that energy, then the scientific classification for that organism is an autotroph (specifically a photoautotroph).

If sunlight cannot reach the bottom of an ocean or deep underground, and if life is found in those locations, then that life must use an alternative like breaking down chemicals from volcanic vents to survive.

If light spreads out in a sphere as it travels away from a star, then the energy is spread over a larger area; if the area increases with distance squared, then the energy per square meter must decrease.