Grades 6-8 or Adult Building Learner
The Sun is really important for life as we know it, since the Sun is the source of nearly all Earth’s warmth. At our distance from the Sun, it’s not so cold that the oceans freeze solid and it’s not so hot that the oceans evaporate into the atmosphere. It’s just the right temperature to have liquid water on the surface of our planet. This is such an important thing to have happen that we gave it a name. We call the area around a star where a planet can be at just the right temperature for liquid water to exist the Goldilocks Zone. This comes from the old story of Goldilocks and the Three Bears, where the main character finds that something can be too hot, too cold, or just right. Since having a planet that’s just right for liquid water is important for living things, one important place for us to look for possible alien life is on planets that are also in the Goldilocks Zone around their stars.
There are probably several hundred billion planets in our galaxy. As we keep finding more planets around other stars, a lot of astrobiologists are really interested in looking at those planets that are in the Goldilocks Zone around their stars. Also, since stars get hotter as they get older, the Goldilocks Zone around a star can actually move out over time. So, it’s also important to look at the planets that stay in the Goldilocks Zone as their stars get older. This area is called the Continuous Goldilocks Zone. Our planet Earth is in this zone around our star!
Are all stars the same as the Sun? No. Some stars are smaller, dimmer, and redder while others are larger, brighter, and white or blue. This tells us that there is a different size for the Goldilocks Zone for each type of star depending on its brightness. Larger stars have wider Goldilocks Zones, which may include more planets. However, large stars burn their fuel faster and do not exist as main sequence stars for a really long time and there aren’t a lot of them in the universe. Stars that are smaller than the Sun last a very long time and there are a lot of them, but many have smaller Goldilocks Zones with less planets or even no planets in them.
Stars that are similar to our Sun, kind of average in size, may be good planetary system candidates because their Goldilocks Zones can be big enough to have at least a few planets and they exist much longer than the really big blue and white stars. The only example of life we are aware of is around this kind of star. Categorizing stars and planets by their potential for liquid water allows researchers to more efficiently search for life. With so many planets out there to search, narrowing it down is helpful.
It also turns out that the distance from a star isn’t the only thing that matters when it comes to how hot a planet will be. The atmosphere of a planet also affects its surface temperature. On Earth, greenhouse gases like water vapor, carbon dioxide, and methane keep warmth at the surface, much like a blanket. Earth is much warmer than it would be without these greenhouse gases. But too much of an atmosphere can make a planet too hot. Venus isn’t the closest planet to the Sun (that’s Mercury), but Venus has the hottest surface because it has a really thick atmosphere.
Considering if planets have atmospheres and how close to their stars they are helps us to narrow the search for life beyond Earth. However, there are worlds in our solar system that are not in the Goldilocks Zone and yet may have had life in the past or may even have life on them right now. These are places like Mars, Titan, Europa, and Enceladus. As astrobiologists search for life out there they consider all of the possible places where life is most likely to survive and flourish.
Disciplinary Core Ideas
PS3.A: Definitions of Energy: Motion energy is properly called kinetic energy; it is proportional to the mass of the moving object and grows with the square of its speed. (MS-PS3-1) ▪A system of objects may also contain stored (potential) energy, depending on their relative positions. (MS-PS3-2) Temperature is a measure of the average kinetic energy of particles of matter. The relationship between the temperature and the total energy of a system depends on the types, states, and amounts of matter present. (MS-PS3-3, MS-PS3-4)
PS3.D: Energy in Chemical Processes and Everyday Life: The chemical reaction by which plants produce complex food molecules (sugars) requires an energy input (i.e., from sunlight) to occur. In this reaction, carbon dioxide and water combine to form carbon-based organic molecules and release oxygen. (MS-LS1-6)
LS2.C: Ecosystem Dynamics, Functioning, and Resilience: Biodiversity describes the variety of species found in Earth’s terrestrial and oceanic ecosystems. The completeness or integrity of an ecosystem’s biodiversity is often used as a measure of its health. (MS-LS2-5)
ESS1.A: The Universe and Its Stars: Patterns of the apparent motion of the Sun, the Moon, and stars in the sky can be observed, described, predicted, and explained with models. (MS-ESS1-1) ▪ Earth and its solar system are part of the Milky Way galaxy, which is one of many galaxies in the universe. (MS-ESS1-2)
ESS1.B: Earth and the Solar System: The solar system consists of the Sun and a collection of objects, including planets, their Moons, and asteroids that are held in orbit around the Sun by its gravitational pull on them. (MS-ESS1-2, MS-ESS1-3)
ESS2.A: Earth’s Materials and Systems: All Earth processes are the result of energy flowing and matter cycling within and among the planet’s systems. This energy is derived from the Sun and Earth’s hot interior. The energy that flows and matter that cycles produce chemical and physical changes in Earth’s materials and living organisms. (MS-ESS2-1)
ESS2.C: The Roles of Water in Earth’s Surface Processes: Water continually cycles among land, ocean, and atmosphere via transpiration, evaporation, condensation and crystallization, and precipitation, as well as downhill flows on land. (MS-ESS2-4) ▪ Global movements of water and its changes in form are propelled by sunlight and gravity. (MS-ESS2-4)
ESS3.A: Natural Resources: Humans depend on Earth’s land, ocean, atmosphere, and biosphere for many different resources. Minerals, fresh water, and biosphere resources are limited, and many are not renewable or replaceable over human lifetimes. These resources are distributed unevenly around the planet as a result of past geologic processes. (MS-ESS3-1)
ESS2.D: Weather and Climate: Weather and climate are influenced by interactions involving sunlight, the ocean, the atmosphere, ice, landforms, and living things. These interactions vary with latitude, altitude, and local and regional geography, all of which can affect oceanic and atmospheric flow patterns. (MS-ESS2-6) *The ocean exerts a major influence on weather and climate by absorbing energy from the Sun, releasing it over time, and globally redistributing it through ocean currents. (MS-ESS2-6)
Cause and Effect: Cause and effect relationships may be used to predict phenomena in natural or designed systems. (MS-ESS2-5) Systems and System Models ▪ Models can be used to represent systems and their interactions — such as inputs, processes and outputs — and energy, matter, and information flows within systems. (MS-ESS2-6)
Big Ideas: The Goldilocks Zone is the area around a star where a planet can maintain the temperature necessary for liquid water to exist. Because Earth is in the Goldilocks Zone of the Sun, it is the right temperature to have the liquid water necessary for life. While there are billions of planets in the galaxy, planets that are in the Goldilocks Zone around their stars are of particular interest in the search for life beyond Earth. A planet’s atmosphere also helps maintain surface temperature and is critical for life.
Boundaries: Students in this grade band develop models to show gravity as the force that holds together the solar system and Milky Way galaxy and controls orbital motions within them. Examples of models can be physical (such as the analogy of distance along a football field or computer visualizations of elliptical orbits) or conceptual (such as mathematical proportions relative to the size of familiar objects such as students’ school or state). MS-ESS1-2
K-8 Searching for the Sun. In this activity (two to four 45 minute lessons) about sunlight as an energy source, learners create a plant box and observe that a plant grows toward the Sun, its primary source of energy. This lesson also includes a hands-on activity about habitability connected to the book, The Day Joshua Jumped Too Much. NASA Goddard Space Flight Center.. https://sdo.gsfc.nasa.gov/assets/docs/Book1_resources.pdf#page=3
5-9 Project Spectra: Planet Designer: Martian Makeover. This is an activity (two 50-minute lessons) about the atmospheric conditions (greenhouse strength, atmospheric thickness) Mars needs to maintain surface water. Learners use a computer interactive to learn about Mars past and present before exploring the pressure and greenhouse strength needed for Mars to have a watery surface as it had in the past. This lesson is part of Project Spectra, a science and engineering education program focusing on how light is used to explore the Solar System. University of Colorado, Boulder/NASA. http://lasp.colorado.edu/home/wp-content/uploads/2013/06/martian_makeover_teacher_20130617.pdf
6-8 SpaceMath Problem 545: Measuring Atmospheric Trace Gases Using Parts Per Million. Students convert from percentage units to parts per million and compare trace gases in the atmospheres of various planets. [Topics: percentages; unit conversions] https://spacemath.gsfc.nasa.gov/Grade67/10Page8.pdf
6-8 SpaceMath Problem 544: The Composition of Planetary Atmospheres. Students study the composition of planetary atmospheres and compare the amounts of certain compounds in them [Topics: pie graphs; percentages; scientific notation] https://spacemath.gsfc.nasa.gov/Grade67/10Page7.pdf
6-8 SpaceMath Problem 335: Methane Lakes on Titan. Students use a recent Cassini radar image of the surface of Titan to estimate how much methane is present in the lakes that fill the image, and compare the volume to that of the freshwater lake, Lake Tahoe. [Topics: estimating irregular areas; calculating volume from area x height; scaled images] https://spacemath.gsfc.nasa.gov/Grade67/6Page148.pdf
6-8 SpaceMath Problem 403: The Goldilocks Planets – Not too hot or cold. Students use a table of the planets discovered by the Kepler satellite, and estimate the number of planets in our Milky Way galaxy that are about the same size as Earth and located in their Habitable Zones. They estimate the average temperature of the planets, and study their tabulated properties using histograms. [Topics: averaging; histogramming] https://spacemath.gsfc.nasa.gov/astrob/7Page66.pdf
6-8 or 9-12 Mars Image Analysis. In this one-three hour lesson, students analyze and interpret the accompanying large-format images of Mars taken by NASA’s Mars Thermal Emission Imaging System (THEMIS) camera. The analysis involves identifying geologic features, calibrating the size of those features, and determining surface history. The lesson culminates in students conducting in-depth research on questions generated during their analyses. Can be used independently or part of the Mars Science Imaging Project through Arizona State University. NASA/Arizona State University. http://marsed.asu.edu/mars-image-analysis
6-9 Planet Hunters Education Guide. Lesson 3: Finding the habitable zone (page 41). This activity explores four types of stars and their characteristics, such as color, temperature, size, and lifespan. These characteristics are then used to determine the conditions for planets around each of them. Next, students compare and contrast their results to develop ideas about where it is reasonable to expect that life could be found outside our own solar system. This lesson is part of a nine lesson unit that takes learners through engaging activities that feature habitability, identifying and characterizing exoplanets, and citizen science. NASA. https://s3.amazonaws.com/zooniverse-resources/zoo-teach/production/uploads/resource/attachment/122/Planet_Hunters_Educator_Guide.pdf
6-9 Rising Stargirls Teaching and Activity Handbook: A public service announcement (PSA) for Life (page 57). Students work cooperatively in teams to solidify the concept of what life needs to survive. Each team pursues an in-depth study of a particular planetary environment and its prospects for life, then presents this information as a PSA to the larger class. Rising Stargirls is a 10-day workshop dedicated to encouraging girls of all backgrounds to learn, explore, and discover the universe through interactive astronomy using theater, writing, and visual art. This provides an avenue for individual self-expression and personal exploration that is interwoven with scientific engagement and discovery. Rising Stargirls. https://static1.squarespace.com/static/54d01d6be4b07f8719d7f29e/t/5748c58ec2ea517f705c7cc6/1464386959806/Rising_Stargirls_Teaching_Handbook.compressed.pdf
6-12 Astrobiology Math. This collection of math problems provides an authentic glimpse of modern astrobiology science and engineering issues, often involving actual research data. Students explore concepts in astrobiology through calculations. Relevant topics include Habitability Zones and Stellar Luminosity (page 57) and The Greenhouse Effect and Planetary Temperature (page 41). NASA. https://www.nasa.gov/pdf/637832main_Astrobiology_Math.pdf
6-12 Extreme Planet Makeover. This online interactive allows students to change the settings of a planet’s size, distance to star, age, and type of star it orbits in order to understand the habitability zone. The habitability zone is a very important concept in astrobiology and is tied to CLQ1.2 in terms of the creation of Earth as a habitable environment. NASA. https://exoplanets.nasa.gov/interactable/1/index.html
6-12 (3-5 adaptable) Project Spectra! – Goldilocks and the Three Planets. In this lesson (two class periods), students determine what some of Earth, Venus, and Mars’ atmosphere is composed of and then mathematically compare the amount of greenhouse gas and CO2 on the planets of Venus, Earth, and Mars, in order to determine which has the most. Students brainstorm to figure out what things, along with greenhouse gases, can affect a planet’s temperature which can determine its habitability. University of Colorado, Boulder/NASA. http://lasp.colorado.edu/home/wp-content/uploads/2011/08/Goldilocks.pdf
6-12 Ocean Worlds. In this web interactive, students learn about water on Earth, in the cosmos and on other planetary bodies. It tells the story of water from its creation and its delivery to the Earth, as well as up-to-date information about water on planetary bodies within the Solar System such as Mars, Europa and others and far away in a variety of places such as planet formation nebulae and exoplanets. The learner comes away with a true sense of how common water is in the universe. NASA. https://www.nasa.gov/specials/ocean-worlds/
7-8 Life Underground. This game is an interactive outreach experience for 7th and 8th grade classrooms. Life Underground is presented in a video game experience that is highly motivating for students. The goal is for students to visualize microscopic life at a range of terrestrial and extraterrestrial subsurface conditions. Students take the role of a young scientist investigating extreme subsurface environments for microbial life. They navigate through extreme conditions, including those of temperature, pressure, acidity, and energy limitations, and they begin to recognize what characterizes life in this context. NASA Astrobiology Institute. https://gameinnovationlab.itch.io/life-underground
8-10 SpaceMath Problem 124: The Moon’s Atmosphere! Students learn about the moon’s very thin atmosphere by calculating its total mass in kilograms using the volume of a spherical shell and the measured density. [Topics: volume of sphere, shell; density-mass-volume; unit conversions] https://spacemath.gsfc.nasa.gov/moon/4Page26.pdf
8-10 SpaceMath Problem 292: How Hot is That Planet? Students use a simple function to estimate the temperature of a recently discovered planet called CoRot-7b. [Topics: algebra II; evaluating power functions] https://spacemath.gsfc.nasa.gov/astrob/6Page61.pdf
8-10 SpaceMath Problem 264: Water on Planetary Surfaces. Students work with watts and Joules to study melting ice. [Topics: unit conversion, rates] https://spacemath.gsfc.nasa.gov/astrob/Astro3.pdf
8-10 SpaceMath Problem 263: Ice or Water? Whether a planetary surface contains ice or liquid water depends on how much heat is available. Students explore the concepts of specific heat and latent heat of fusion to better understand and quantify the energy required for liquid water to exist under various conditions. [Topics: unit conversion, scientific notation] https://spacemath.gsfc.nasa.gov/astrob/Astro1.pdf