What is life?
Name one characteristic that distinguishes living things from non-living things
Living things are made of cells, use energy, grow, reproduce, or respond to stimuli
What are the three basic needs of life?
Water, energy, and nutrients
What is An organism that can survive in extreme conditions
What makes a planet or moon "habitable"?
It has the right conditions for liquid water, energy, and nutrients
What is A formula used to estimate the number of civilizations in our galaxy
What is evidence of past or present life?
biosignature
What makes water so important for life?
It dissolves and transports nutrients needed for chemical reactions
Which type of extremophile can survive in extremely high temperatures, and where is it commonly found?
Thermophiles; they are found in places like hydrothermal vents and hot springs
Which moon of Jupiter is thought to have an ocean under its ice?
Europa
What kind of signals do scientists search for to detect alien life?
Radio signals or chemical signatures
Why is defining life difficult for scientists?
Some things share only some characteristics of life
Why is sunlight important for life on Earth?
It provides energy for photosynthesis, the foundation of many food chains
Some extremophiles can survive in highly salty environments, such as salt flats or the Dead Sea. What are these organisms called?
Halophiles
What role does an atmosphere play in habitability?
it protects from radiation and helps regulate temperature
What is one argument that supports the idea that life is common in the universe?
The vast number of planets that could have life-friendly conditions
What two traits are most useful for distinguishing life from non-life?
The ability to reproduce and evolve
Name one energy source that life can use besides sunlight
Chemical energy from compounds like sulfides or methane
Which type of extremophile can endure extreme levels of radiation?
Radioresistant extremophiles
What is the region around a star where conditions are just right for liquid water?
Goldilocks zone
Scientists use powerful telescopes to search for exoplanets that could support life. What is one method they use to detect exoplanets?
The transit method—astronomers observe a star’s brightness over time, and if a planet passes in front of it, the light dims temporarily, indicating the presence of an exoplanet
Viruses can reproduce and evolve, but they cannot carry out metabolic processes on their own. Based on the scientific definition of life, are viruses considered living? Explain why or why not.
No, viruses are not considered fully alive because they cannot carry out metabolism or reproduce without a host cell. They rely on infecting a host to make copies of themselves
What is one way scientists search for life beyond Earth?
Looking for liquid water or chemical signs of life on other planets
An organism is discovered living under the Martian surface, where there is little oxygen and a constant supply of methane. Based on Earth's extremophiles, which type of extremophile would this organism most likely resemble?
Anaerobe
Why is Mars considered a possible home for life?
Evidence of past liquid water and underground ice deposits
Why haven’t we found extraterrestrial life yet?
Life may be rare, too far away, or not using technology we can detect.