Discover opportunities to engage students in science, technology, engineering and math (STEM) with lessons and resources inspired by the latest happenings at NASA.
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Teachable Moments | May 18, 2018
NASA Mission Gets the View on Earth’s Water Resources from Space
In the News
A pair of Earth orbiters designed to keep track of the planet's water resources and evolving water cycle is scheduled to launch this month – no earlier than May 22, 2018. The Gravity Recovery and Climate Experiment Follow-On mission, or GRACE-FO, will pick up where its predecessor, GRACE, left off when it completed its 15-year mission in 2017. By measuring changes in Earth’s gravity, the mission will track water movement around the globe, identifying risks such as droughts and floods and revealing how land ice and sea level are evolving. The GRACE-FO mission is a great way to get students asking, and answering, questions about how we know what we know about some of the major components of Earth’s water cycle: ice sheets, glaciers, sea level, and ground-water resources.
How It Works
Earth Science Lessons
Explore a collection of standards-aligned lessons for grades K-12 all about our home planet.
The GRACE-FO mission, a partnership between NASA and the German Research Centre for Geosciences (GFZ), will measure small variations in Earth’s mass to track how and where water is moving across the planet. This is no easy task, as water can be solid, liquid or gas; it can be in plain sight (as in a lake or glacier); it can be in the atmosphere or hidden underground; and it’s always on the move. But one thing all this water has in common, regardless of what state of matter it is in or where it is located, is mass.
Everything that has mass exerts a gravitational force. It is this gravitational force that GRACE-FO measures to track the whereabouts of water on Earth. Most of Earth's gravitational force, more than 99 percent, does not change from one month to the next because it is exerted by Earth’s solid surface and interior. GRACE-FO is sensitive enough to measure the tiny amount that does change – mostly as a result of the movement of water within the Earth system.
GRACE-FO works by flying two spacecraft in tandem around Earth – one spacecraft trailing the other at a distance of about 137 miles (220 kilometers). By pointing their microwave ranging instruments at each other, the satellites can measure tiny changes in the distance between them – within one micron (the diameter of a blood cell) – caused by changes in Earth’s gravitational field. Scientists can then use those measurements to create a map of Earth’s global gravitational field and calculate local mass variations.
As the forward spacecraft travels over a region that has more or less mass than the surrounding areas, such as a mountain or low valley, the gravitational attraction of that mass will cause the spacecraft to speed up or slow down, slightly increasing or decreasing the relative distance between it and its trailing companion. As a result of this effect, GRACE-FO will be able to track water as it moves into or out of a region, changing the region’s mass and, therefore, its gravity. In fact, the previous GRACE spacecraft measured a weakening gravity field over several years in Central California, enabling an estimate of aquifer depletion, and in Greenland, providing accurate measurements of ice melt over more than 15 years.
Find out more about how the mission works in the video below, from JPL's "Crazy Engineering" video series:
Why It’s Important
Tracking changes in our water resources and the water cycle is important for everyone. The water cycle is one of the fundamental processes on Earth that sustains life and shapes our planet, moving water between Earth's oceans, atmosphere and land. Over thousands of years, we have developed our civilizations around that cycle, placing cities and agriculture near rivers and the sea, building reservoirs and canals to bring water to where it is needed, and drilling wells to pump water from the ground. We depend on this cycle for the water resources that we need, and as those resources change, communities and livelihoods are affected. For example, too much water in an area causes dangerous floods that can destroy property, crops and infrastructure. Too little water causes shortages, which require us to reduce how much water we use. GRACE-FO will provide monthly data that will help us study those precious water resources.
A map of groundwater storage trends for Earth's 37 largest aquifers using GRACE data shows depletion and replenishment in millimeters of water per year. Twenty-one aquifers have exceeded sustainability tipping points and are being depleted, and 13 of these are considered significantly distressed, threatening regional water security and resilience. Image credit: NASA/JPL-Caltech
Changes to Earth’s water over multiple years are an important indicator of how Earth is responding in a changing climate. Monitoring changes in ice sheets and glaciers, surface and underground water storage, the amount of water in large lakes and rivers, as well as changes in sea level and ocean currents, provides a global view of how Earth’s water cycle and energy balance are evolving. As our climate changes and our local water resources shift, we need accurate observations and continuous measurements like those from GRACE and GRACE Follow-On to be able to respond and plan.
As a result of the GRACE mission, we have a much more accurate picture of how our global water resources are evolving in both the short and long term. GRACE-FO will continue the legacy of GRACE, yielding up-to-date water and surface mass information and allowing us to identify trends over the coming years.
Teach It
Have students interpret GRACE data for themselves:
Get students learning about global water resources:
Teach students to read, interpret and compare “heat map” representations of Earth science data:
Explore More
Try these related resources for students from NASA's Space Place:
Teachable Moments | April 24, 2018
NASA InSight Lander to Get First Look at ‘Heart’ of Mars
In the News
A spacecraft designed to study seismic activity on Mars, or “marsquakes,” is scheduled to lift off on a nearly seven-month journey to the Red Planet on May 5, 2018.
NASA’s InSight Mars lander is designed to get the first in-depth look at the “heart” of Mars: its crust, mantle and core. In other words, it will be the Red Planet’s first thorough checkup since it formed 4.5 billion years ago. The launch, from Vandenberg Air Force Base in Central California, also marks a first: It will be the first time a spacecraft bound for another planet lifts off from the West Coast. It’s a great opportunity to get students excited about the science and math used to launch rockets and explore other planets.
How It Works
Mars Lessons
Explore our collection of standards-aligned, STEM lessons all about Mars and missions to the Red Planet.
NASA usually launches interplanetary spacecraft from the East Coast, at Cape Canaveral in Florida, to provide them with a momentum boost from Earth’s easterly rotation. It’s similar to how running in the direction you are throwing a ball can provide a momentum boost to the ball. If a spacecraft is launched without that extra earthly boost, the difference must be made up by the rocket engine. Since InSight is a small, lightweight spacecraft, its rocket can easily accommodate getting it into orbit without the help of Earth’s momentum.
Scheduled to launch no earlier than 4:05 a.m. PDT on May 5, InSight will travel aboard an Atlas V 401 launch vehicle on a southerly trajectory over the Pacific Ocean. (Here's how to watch the launch in person or online.) If the weather is bad or there are any mechanical delays, InSight can launch the next day. In fact, InSight can launch any day between May 5 and June 8, a time span known as a launch period, which has multiple launch opportunities during a two-hour launch window each day.
Regardless of the date when InSight launches, its landing on Mars is planned for November 26, 2018, around noon PST. Mission controllers can account for the difference in planetary location between the beginning of the launch window and the end by varying the amount of time InSight spends in what’s called a parking orbit. A parking orbit is a temporary orbit that a spacecraft can enter before moving to its final orbit or trajectory. For InSight, the Atlas V 401 will boost the spacecraft into a parking orbit where it will coast for a while to get into proper position for an engine burn that will send it toward Mars. The parking orbit will last 59 to 66 minutes, depending on the date and time of the launch.
Why It’s Important
Previous missions to Mars have investigated the history of the Red Planet’s surface by examining features like canyons, volcanoes, rocks and soil. However, many important details about the planet's formation can only be found by studying the planet’s interior, far below the surface. And to do that, you need specialized instruments and sensors like those found on InSight.
The InSight mission, designed to operate for one Mars year (approximately two Earth years), will use its suite of instruments to investigate the interior of Mars and uncover how a rocky body forms and becomes a planet. Scientists hope to learn the size of Mars’ core, what it’s made of and whether it’s liquid or solid. InSight will also study the thickness and structure of Mars’ crust, the structure and composition of the mantle and the temperature of the planet’s interior. And a seismometer will determine how often Mars experiences tectonic activity, known as “marsquakes,” and meteorite impacts.
Together, the instruments will measure Mars’ vital signs: its "pulse" (seismology), "temperature" (heat flow), and "reflexes" (wobble). Here’s how they work:
This labeled artist's concept depicts the NASA InSight Mars lander at work studying the interior of Mars.
InSight’s seismometer is called SEIS, or the Seismic Experiment for Interior Structure. By measuring seismic vibrations across Mars, it will provide a glimpse into the planet’s internal activity. The volleyball-size instrument will sit on the Martian surface and wait patiently to sense the seismic waves from marsquakes and meteorite impacts. These measurements can tell scientists about the arrangement of different materials inside Mars and how the rocky planets of the solar system first formed. The seismometer may even be able to tell us if there's liquid water or rising columns of hot magma from active volcanoes underneath the Martian surface.
The Heat Flow and Physical Properties Probe, HP3 for short, burrows down almost 16 feet (five meters) into Mars' surface. That's deeper than any previous spacecraft arms, scoops, drills or probes have gone before. Like studying the heat leaving a car engine, HP3 will measure the heat coming from Mars' interior to reveal how much heat is flowing out and what the source of the heat is. This will help scientists determine whether Mars formed from the same material as Earth and the Moon, and will give them a sneak peek into how the planet evolved.
InSight’s Rotation and Interior Structure Experiment, or RISE, instrument tracks tiny variations in the location of the lander. Even though InSight is stationary on the planet, its position in space will wobble slightly with Mars itself, as the planet spins on its axis. Scientists can use what they learn about the Red Planet’s wobble to determine the size of Mars’ iron-rich core, whether the core is liquid, and which other elements, besides iron, may be present.
When InSight lifts off, along for the ride in the rocket will be two briefcase-size satellites, or CubeSats, known as MarCO, or Mars Cube One. They will take their own path to Mars behind InSight, arriving in time for landing. If all goes as planned, as InSight enters the Martian atmosphere, MarCO will relay data to Earth about entry, descent and landing operations, potentially faster than ever before. InSight will also transmit data to Earth the way previous Mars spacecraft have, by using NASA’s Mars Reconnaissance Orbiter as a relay. MarCO will be the first test of CubeSat technology at another planet, and if successful, it could provide a new way to communicate with spacecraft in the future, providing news of a safe landing – or any potential problems – sooner.
Thanks to the Mars rovers, landers and orbiters that have come before, scientists know that Mars has low levels of geological activity – but a lander like InSight can reveal what might be lurking below the surface. And InSight will give us a chance to discover more not just about the history of Mars, but also of our own planet’s formation.
Teach It
When launching to another planet, we want to take the most efficient route, using the least amount of rocket fuel possible. To take this path, we must launch during a specific window of time, called a launch window. Use this lesson in advanced algebra to estimate the launch window for the InSight lander and future Mars missions.
SEIS will record the times that marsquake surface waves arrive at the lander. Try your hand, just like NASA scientists, using these times, a little bit of algebra and the mathematical constant π to determine the timing and location of a marsquake!
Take students on a journey to Mars with this set of 19 standards-aligned STEM lessons that can be modified to fit various learning environments, including out-of-school time.
Build, test and launch your very own air-powered rocket to celebrate the first West Coast interplanetary spacecraft launch!
Explore More
- InSight Launch Toolkit - Find out more about the launch, including how to watch in person or online
- InSight Mission website
- InSight Mission Roadshow
- NASA Mars Exploration website
- Marsquake lessons and resources for teachers from the British Geological Survey
- Modeling Seismic Waves with Slinkies from the Incorporated Research Institutions for Seismology (IRIS)
- Make a Human Wave from IRIS
- Make an Earthquake Machine from IRIS
Try these related resources for students from NASA's Space Place:
Teachable Moments | April 23, 2018
May the Force = mass x acceleration
This feature was originally published on May 3, 2016.
In the News
What do "Star Wars," NASA's Dawn spacecraft and Newton's Laws of Motion have in common? An educational lesson that turns science fiction into science fact using spreadsheets – a powerful tool for developing the scientific models addressed in the Next Generation Science Standards.
May the 4th Lessons
Celebrate Star Wars Day with these standards-aligned lessons in motion and forces for grades K-12.
The TIE (Twin Ion Engine) fighter is a staple of the "Star Wars" universe. Darth Vader flew one in "A New Hope." Poe Dameron piloted one in "The Force Awakens." And many, many Imperial pilots met their fates in them. While the fictional TIE fighters in "Star Wars" flew a long time ago in a galaxy far, far away, ion engines are a reality in this galaxy today – and have a unique connection to NASA’s Jet Propulsion Laboratory.
Launched in 1998, the first spacecraft to use an ion engine was Deep Space 1, which flew by asteroid 9969 Braille and comet Borrelly. Fueled by the success of Deep Space 1, engineers at JPL set forth to develop the next spacecraft that would use ion propulsion. This mission, called Dawn, would take ion-powered spacecraft to the next level by allowing Dawn to go into orbit twice – around the two largest objects in the asteroid belt: Vesta and Ceres.
How Does It Work?
Ion engines rely on two principles that Isaac Newton first described in 1687. First, a positively charged atom (ion) is pushed out of the engine at a high velocity. Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction, so then a small force pushes back on the spacecraft in the opposite direction – forward! According to Newton’s Second Law of Motion, there is a relationship between the force (F) exerted on an object, its mass (m) and its acceleration (a). The equation F=ma describes that relationship, and tells us that the small force applied to the spacecraft by the exiting atom provides a small amount of acceleration to the spacecraft. Push enough atoms out, and you'll get enough acceleration to really speed things up.
Why is It Important?
Compared with traditional chemical rockets, ion propulsion is faster, cheaper and safer:
- Faster: Spacecraft powered by ion engines can reach speeds of up to 90,000 meters per second (more than 201,000 mph!)
- Cheaper: When it comes to fuel efficiency, ion engines can reach more than 90 percent fuel efficiency, while chemical rockets are only about 35 percent efficient.
- Safer: Ion thrusters are fueled by inert gases. Most of them use xenon, which is a non-toxic, chemically inert (no risk of exploding), odorless, tasteless and colorless gas.
These properties make ion propulsion a very attractive solution when engineers are designing spacecraft. While not every spacecraft can use ion propulsion – some need greater rates of acceleration than ion propulsion can provide – the number and types of missions using these efficient engines is growing. In addition to being used on the Dawn spacecraft and communication satellites orbiting Earth, ion propulsion could be used to boost the International Space Station into higher orbits and will likely be a part of many future missions exploring our own solar system.
Teach It
Newton’s Laws of Motion are an important part of middle and high school physical science and are addressed specifically by the Next Generation Science Standards as well as Common Core Math standards. The lesson "Ion Propulsion: Using Spreadsheets to Model Additive Velocity" lets students study the relationship between force, mass and acceleration as described by Newton's Second Law as they develop spreadsheet models that apply those principles to real-world situations.
This lesson meets the following Next Generation Science and Common Core Math Standards:
NGSS Standards:
- MS-PS2-2: Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.
- HS-PS2-1: Analyze data to support the claim that Newton’s second law of motion describes the mathematical relationship among the net force on a macroscopic object, its mass, and its acceleration.
- HS-PS2-1: Use mathematical representations to support the claim that the total momentum of a system of objects is conserved when there is no net force on the system.
Common Core Math Standards:
Grade 8: Expressions and Equations A.4: Perform operations with numbers expressed in scientific notation, including problems where both decimal and scientific notation are used. Use scientific notation and choose units of appropriate size for measurements of very large or very small quantities (e.g., use millimeters per year for seafloor spreading). Interpret scientific notation that has been generated by technology.
High School: Algebra CED.A.4: Rearrange formulas to highlight a quantity of interest, using the same reasoning as in solving equations.
High School: Functions LE.A: Construct and compare linear, quadratic, and exponential models and solve problems.
High School: Functions BF.A.1: Write a function that describes a relationship between two quantities.
High School: Statistics and Probability ID.C: Interpret linear Models
High School: Number and Quantity Q.A.1: Use units as a way to understand problems and to guide the solution of multi-step problems; choose and interpret units consistently in formulas; choose and interpret the scale and the origin in graphs and data displays."
Explore More
- Website: Dawn Mission
- Blog: Dawn Journal
- Video: Crazy Engineering - Ion Propulsion
- Ion propulsion interactives
- Eyes on the Solar System: Dawn Mission Tour (scroll to "Solar System Tours" and click the "Dawn" link)
TAGS: May the Fourth, Star Wars Day, F=ma, ion propulsion, Dawn, Deep Space 1, lesson, classroom activity, NGSS, Common Core Math
Teachable Moments | March 9, 2018
Pi Goes the Distance at NASA
Update: March 15, 2018 – The answers to the 2018 NASA Pi Day Challenge are here! View the illustrated answer key
In the News
The 2018 NASA Pi Day Challenge
Can you solve these stellar mysteries with pi? Click to get started.
Pi Day, the annual celebration of one of mathematics’ most popular numbers, is back! Representing the ratio of a circle’s circumference to its diameter, pi has many practical applications, including the development and operation of space missions at NASA’s Jet Propulsion Laboratory.
The March 14 holiday is celebrated around the world by math enthusiasts and casual fans alike – from memorizing digits of pi (the current Pi World Ranking record is 70,030 digits) to baking and eating pies.
JPL is inviting people to participate in its 2018 NASA Pi Day Challenge – four illustrated math puzzlers involving pi and real problems scientists and engineers solve to explore space, also available as a free poster! Answers will be released on March 15.
Why March 14?
Pi is what’s known as an irrational number, meaning its decimal representation never ends and it never repeats. It has been calculated to more than one trillion digits, but NASA scientists and engineers actually use far fewer digits in their calculations (see “How Many Decimals of Pi Do We Really Need?”). The approximation 3.14 is often precise enough, hence the celebration occurring on March 14, or 3/14 (when written in U.S. month/day format). The first known celebration occurred in 1988, and in 2009, the U.S. House of Representatives passed a resolution designating March 14 as Pi Day and encouraging teachers and students to celebrate the day with activities that teach students about pi.
NASA’s Pi Day Challenge
Lessons: Pi in the Sky
Explore the entire NASA Pi Day Challenge lesson collection, including free posters and handouts!
To show students how pi is used at NASA and give them a chance to do the very same math, the JPL Education Office has once again put together a Pi Day challenge featuring real-world math problems used for space exploration. This year’s challenge includes exploring the interior of Mars, finding missing helium in the clouds of Jupiter, searching for Earth-size exoplanets and uncovering the mysteries of an asteroid from outside our solar system.
Here’s some of the science behind this year’s challenge:
Scheduled to launch May 5, 2018, the InSight Mars lander will be equipped with several scientific instruments, including a heat flow probe and a seismometer. Together, these instruments will help scientists understand the interior structure of the Red Planet. It’s the first time we’ll get an in-depth look at what’s happening inside Mars. On Earth, seismometers are used to measure the strength and location of earthquakes. Similarly, the seismometer on Insight will allow us to measure marsquakes! The way seismic waves travel through the interior of Mars can tell us a lot about what lies beneath the surface. This year’s Quake Quandary problem challenges students to determine the distance from InSight to a hypothetical marsquake using pi!
Also launching in spring is NASA’s Transiting Exoplanet Survey Satellite, or TESS, mission. TESS is designed to build upon the discoveries made by NASA’s Kepler Space Telescope by searching for exoplanets – planets that orbit stars other than our Sun. Like Kepler, TESS will monitor hundreds of thousands of stars across the sky, looking for the temporary dips in brightness that occur when an exoplanet passes in front of its star from the perspective of TESS. The amount that the star dims helps scientists determine the radius of the exoplanet. Like those exoplanet-hunting scientists, students will have to use pi along with data from Kepler to find the size of an exoplanet in the Solar Sleuth challenge.
Jupiter is our solar system’s largest planet. Shrouded in clouds, the planet’s interior holds clues to the formation of our solar system. In 1995, NASA’s Galileo spacecraft dropped a probe into Jupiter’s atmosphere. The probe detected unusually low levels of helium in the upper atmosphere. It has been hypothesized that the helium was depleted out of the upper atmosphere and transported deeper inside the planet. The extreme pressure inside Jupiter condenses helium into droplets that form inside a liquid metallic hydrogen layer below. Because the helium is denser than the surrounding hydrogen, the helium droplets fall like rain through the liquid metallic hydrogen. In 2016, the Juno spacecraft, which is designed to study Jupiter’s interior, entered orbit around the planet. Juno’s initial gravity measurements have helped scientists better understand the inner layers of Jupiter and how they interact, giving them a clearer window into what goes on inside the planet. In the Helium Heist problem, students can use pi to find out just how much helium has been depleted from Jupiter’s upper atmosphere over the planet’s lifetime.
In October 2017, astronomers spotted a uniquely-shaped object traveling in our solar system. Its path and high velocity led scientists to believe ‘Oumuamua, as it has been dubbed, is actually an object from outside of our solar system – the first ever interstellar visitor to be detected – that made its way to our neighborhood thanks to the Sun’s gravity. In addition to its high speed, ‘Oumuamua is reflecting the Sun’s light with great variation as the asteroid rotates on its axis, causing scientists to conclude it has an elongated shape. In the Asteroid Ace problem, students can use pi to find the rate of rotation for ‘Oumuamua and compare it with Earth’s rotation rate.
Explore More
Join the Conversation
- Join the conversation and share your Pi Day Challenge answers with @NASAJPL_Edu on social media using the hashtag #NASAPiDayChallenge
- Pi Day: What’s Going ‘Round – Tell us what you’re up to this Pi Day and share your stories and photos with NASA.
Standards-Aligned Lessons
- Pi in the Sky 5
- Pi in the Sky 4
- Pi in the Sky 3
- Pi in the Sky 2
- Pi in the Sky
- Pi in the Sky Challenge (slideshow for students)
Multimedia
- 18 Ways NASA Uses Pi – Whether it's sending spacecraft to other planets, driving rovers on Mars, finding out what planets are made of or how deep alien oceans are, pi takes us far at NASA. Find out how pi helps us explore space.
- Kepler-186f Travel Poster
- Video: First Interstellar Asteroid Wows Scientists
- Planet Pi
Facts and Figures
Missions
Websites
TAGS: Pi Day, Math, Science, Engineering, NASA Pi Day Challenge, K-12, Lesson, Activity, Slideshow, Mars, Jupiter, Exoplanets, Kepler, Kepler-186f, Juno, InSight, TESS, ‘Oumuamua, asteroid, asteroids, NEO, Nearth Earth Object
Teachable Moments | January 18, 2018
How to Watch a Total Lunar Eclipse and Get Students Observing the Moon
In the News
A full moon is always a good reason to go outside and turn your head toward the sky, but those who do so early on January 31 will be treated to the sight of what’s being called the super blue blood moon! Super, because the moon will be closest to Earth in its orbit during the full moon (more on supermoons here); blue, because it’s the second full moon in a calendar month; and blood, because there will be a total lunar eclipse that will turn the moon a reddish hue. It’s the only total lunar eclipse (blood moon) visible from North America in 2018, so it’s a great opportunity for students to observe the Moon – and for teachers to make connections to in-class science content.
How It Works
These side-by-side graphics show how the Moon, Sun and Earth align during a lunar eclipse (left) versus a non-eclipse full moon (right). Credit: NASA Goddard Visualization Studio | + Enlarge image
Eclipses can occur when the Sun, the Moon and Earth align. Lunar eclipses can only happen during the full moon phase, when the Moon and the Sun are on opposite sides of Earth. At that point, the Moon could move into the shadow cast by Earth, resulting in a lunar eclipse. However, most of the time, the Moon’s slightly tilted orbit brings it above or below the shadow of Earth.
The time period when the Moon, Earth and the Sun are lined up and on the same plane – allowing for the Moon to pass through Earth’s shadow – is called an eclipse season. Eclipse seasons last about 34 days and occur just shy of every six months. When a full moon occurs during an eclipse season, the Moon travels through Earth’s shadow, creating a lunar eclipse.
When a full moon occurs during an eclipse season, the Moon travels through Earth's shadow, creating a lunar eclipse. Credit: NASA/JPL-Caltech | + Enlarge image
Unlike solar eclipses, which require special glasses to view and can only be seen for a few short minutes in a very limited area, a total lunar eclipse can be seen for about an hour by anyone on the nighttime side of Earth – as long as skies are clear!
Why It’s Important
Lessons About the Moon
Explore our collection of standards-aligned lessons for grades 1-12.
Lunar eclipses have long played an important role in understanding Earth and its motions in space.
In ancient Greece, Aristotle noted that the shadows on the Moon during lunar eclipses were round, regardless of where an observer saw them. He realized that only if Earth were a spheroid would its shadows be round – a revelation that he and others had many centuries before the first ships sailed around the world.
Earth wobbles on its axis like a spinning top that’s about to fall over, a phenomenon called precession. Earth completes one wobble, or precession cycle, over the course of 26,000 years. Greek astronomer Hipparchus made this discovery by comparing the position of stars relative to the Sun during a lunar eclipse to those recorded hundreds of years earlier. A lunar eclipse allowed him to see the stars and know exactly where the Sun was for comparison – directly opposite the Moon. If Earth didn’t wobble, the stars would appear to be in the same place they were hundreds of years earlier. When Hipparchus saw that the stars’ positions had indeed moved, he knew that Earth must wobble on its axis!
Additionally, modern-day astronomers have used ancient eclipse records and compared them with computer simulations. These comparisons helped scientists determine the rate at which Earth’s rotation is slowing.
What to Expect
During a total lunar eclipse, the Moon first enters into the penumbra, or the outer part of Earth's shadow, where the shadow is still penetrated by some sunlight. Credit: NASA | + Enlarge image
As the Moon starts to enter into the umbra, the inner and darker part of Earth's shadow, it appears as if a bite has been taken out of the Moon. This "bite" will grow until the Moon has entered fully into the umbra. Credit: NASA | + Enlarge image
The total lunar eclipse starts once the moon is completely inside the umbra. And the moment of greatest eclipse happens with the Moon is halfway through the umbra as shown in this graphic. Credit: NASA | + Enlarge image
As the Moon moves completely into the umbra, it turns a reddish-orange color. Credit: NASA | + Enlarge image
The Moon passes through two distinct parts of Earth’s shadow during a lunar eclipse. The outer part of the cone-shaped shadow is called the penumbra. The penumbra is less dark than the inner part of the shadow because it’s penetrated by some sunlight. (You have probably noticed that some shadows on the ground are darker than others, depending on how much outside light enters the shadow; the same is true for the outer part of Earth’s shadow). The inner part of the shadow, known as the umbra, is much darker because Earth blocks additional sunlight from entering the umbra.
At 2:51 a.m. PST on January 31, 2018, the edge of the Moon will begin entering the penumbra. The Moon will dim very slightly for the next 57 minutes as it moves deeper into the penumbra. Because this part of Earth’s shadow is not fully dark, you may only notice some dim shading (if anything at all) on the Moon near the end of this part of the eclipse. Should you decide to sleep in during this time, you won’t miss much.
At 3:48 a.m. PST, the edge of the Moon will begin entering the umbra. As the Moon moves into the darker shadow, significant darkening will be noticeable. Some say that during this part of the eclipse, the Moon looks as if it has had a bite taken out of it. That “bite” gets bigger and bigger as the Moon moves deeper into the shadow. If you will be on the East Coast of the United States, you might still be able to see the Moon just as it moves into the umbra before the Moon sets and the Sun rises.
At 4:51 a.m. PST, the Moon will be completely inside the umbra, marking the beginning of the total lunar eclipse. The moment of greatest eclipse, when the Moon is halfway through the umbra, occurs at 5:31 a.m. PST.
As the Moon moves completely into the umbra, something interesting happens: The Moon begins to turn reddish-orange. The reason for this phenomenon? Earth’s atmosphere. As sunlight passes through it, the small molecules that make up our atmosphere scatter blue light, which is why the sky appears blue. This leaves behind mostly red light that bends, or refracts, into Earth’s shadow. We can see the red light during an eclipse as it falls onto the Moon in Earth’s shadow. This same effect is what gives sunrises and sunsets a reddish-orange color.
A variety of factors affect the appearance of the Moon during a total lunar eclipse. Clouds, dust, ash, photochemical droplets and organic material in the atmosphere can change how much light is refracted into the umbra. Additionally, the January 2018 lunar eclipse takes place when the full moon is at or near the closest point in its orbit to Earth (popularly known as a supermoon). This means it is deeper inside the umbra shadow and therefore may appear darker. The potential for variation provides a great opportunity for students to observe and classify the lunar eclipse based on its brightness. Details can be found below in the “Teach It” section.
At 6:07 a.m. PST, the edge of the Moon will begin exiting the umbra and moving into the opposite side of the penumbra. This marks the end of the total lunar eclipse.
At 7:11 a.m. PST, the Moon will be completely outside of the umbra. It will continue moving out of the penumbra until the eclipse ends at 8:08 a.m.
Teach It
Ask students to observe the lunar eclipse and evaluate the Moon’s brightness using the Danjon Scale of Lunar Eclipse Brightness. The Danjon scale illustrates the range of colors and brightness the Moon can take on during a total lunar eclipse and is a tool observers can use to characterize the appearance of an eclipse. View the lesson guide here. After the eclipse, have students compare and justify their evaluations of the eclipse.
Use these standards-aligned lessons and related activities to get your students excited about the eclipse, moon phases and Moon observations.
- *NEW* Evaluating a Lunar Eclipse (Grades 3-12) - Students use the Danjon Scale of Lunar Eclipse Brightness to illustrate the range of colors and brightness the Moon can take on during a total lunar eclipse.
- Observing the Moon (Grades K-6) - Students identify the Moon’s location in the sky and record their observations in a journal over the course of the moon-phase cycle.
- Moon Phases (Grades 1-6) - Students learn about the phases of the Moon by acting them out. In 30 minutes, they will act out one complete, 30-day, Moon cycle.
- Measuring the Supermoon (Grades 5-12) - Students take measurements of the Moon during its full phase over multiple Moon cycles to compare and contrast results.
- Modeling the Earth-Moon System (Grades 6-8) – Students learn about scale models and distance by creating a classroom-size Earth-Moon system.
- Make a Moon Phases Calendar and Calculator – Like a decoder wheel for the Moon, this calendar will show you where and when to see the Moon and every moon phase throughout the year!
Explore More
- Try these related resources for students from NASA's Space Place:
- Lunar Eclipses and Solar Eclipses – This guide for kids provides an overview of lunar and solar eclipses.
- Why Does the Moon Have Craters? – Check out NASA's Space Place for the answer, written just for kids.
- NASA Moon Website – Find out more about the Moon and the NASA robots and humans who have visited it.
TAGS: Lunar Eclipse, Moon, Super Blue Blood Moon, Observe the Moon, Eclipse, K-12, Classroom Activities, Teaching
Teachable Moments | January 12, 2018
Explorer 1 Anniversary Marks 60 Years of Science in Space
In the News
This month marks the 60th anniversary of the launch of America’s first satellite, Explorer 1. The small, pencil-shaped satellite did more than launch the U.S. into the Space Age. With its collection of instruments, or scientific tools, it turned space into not just a new frontier, but also a place of boundless scientific exploration that could eventually unveil secrets of new worlds – as well as the mysteries of our own planet.
A poster highlights the main characteristics of Explorer 1 and the Jupiter C rocket that launched it into space. Image credit: NASA
How They Did It
At the height of competition for access to space, the U.S. and the Soviet Union were both building satellites that would ride atop rockets in a quest to orbit Earth. The Soviets launched Sputnik 1 on October 4, 1957. Shortly thereafter, on January 31, 1958, the U.S. launched Explorer 1, the satellite that would begin a new age of scientific space exploration.
Using rockets to do science from orbit was a brand-new option in the late 1950s. Before this time, rockets had only been used for military operations and atmospheric research. Still, rockets of that era weren’t very reliable and none had been powerful enough to place an object into Earth orbit.
Rocket Activities
Explore our collection of standards-aligned lessons for grades K-9.
In order to lift Explorer 1 to its destination in Earth orbit, an existing U.S. Army rocket, the Jupiter C, was fitted with a fourth stage, provided by the Jet Propulsion Laboratory in Pasadena, California. For this stage, a rocket motor was integrated into the satellite itself. The new, four-stage rocket was called “Juno 1.”
Prior to these first orbiting observatories, everything we knew about space and Earth came from Earth-based observation platforms – sensors and telescopes – and a few atmospheric sounding rockets. With the success of Explorer 1 and the subsequent development of more powerful rockets, we have been able to send satellites beyond Earth orbit to explore planets, moons, asteroids and even our Sun. With a space-based view of Earth, we are able to gain a global perspective and acquire a wide variety and amount of data at a rapid pace.
Why It’s Important
This photograph shows the scientific instruments mounted inside Explorer 1 alongside its outer case. Image Credit: James A. Van Allen Papers (RG 99.0142), University Archives, The University of Iowa Libraries
This graphic shows the various components and science instruments aboard Explorer 1, including its primary science instrument, a cosmic ray detector. Image credit: NASA/JPL-Caltech
This graphic shows a cutaway diagram of the Van Allen belts along with the locations of a few Earth-orbiting spacecraft, including the Van Allen Probes. Image credit: NASA
The primary science instrument on Explorer 1 was a cosmic ray detector designed to measure the radiation environment in Earth orbit – in part, to understand what hazards future spacecraft (or space-faring humans) might face. Once in space, this experiment, provided by James Van Allen of the University of Iowa, revealed a much lower cosmic ray count than expected. Van Allen theorized that the instrument might have been saturated by very strong radiation from a belt of charged particles trapped in space by Earth's magnetic field. The existence of the radiation belts was confirmed over the next few months by Explorer 3, Pioneer 3 and Explorer 4. The belts became known as the Van Allen radiation belts in honor of their discoverer.
Although we discovered and learned a bit about the Van Allen belts with the Explorer missions, they remain a source of scientific interest. The radiation belts are two (or more) donut-shaped regions encircling Earth, where high-energy particles, mostly electrons and ions, are trapped by Earth's magnetic field. The belts shrink and swell in size in response to incoming radiation from the Sun. They protect Earth from incoming high-energy particles, but this trapped radiation can affect the performance and reliability of our technologies, such as cellphone communication, and pose a threat to astronauts and spacecraft. It’s not safe to spend a lot of time inside the Van Allen radiation belts.
Most spacecraft are not designed to withstand high levels of particle radiation and wouldn’t last a day in the Van Allen belts. As a result, most spacecraft travel quickly through the belts toward their destinations, and non-essential instruments are turned off for protection during this brief time.
To conquer the challenge of extreme radiation in the belts while continuing the science begun by Explorer 1, NASA launched a pair of radiation-shielded satellites, the Van Allen Probes, in 2012. (The rocket that carried the Van Allen Probes into space was more than twice as tall as the rocket that carried Explorer 1 to orbit!)
The Van Allen Probes carry identical instruments and orbit Earth, following one another in highly elliptical, nearly identical orbits. These orbits bring the probes as close as about 300 miles (500 kilometers) above Earth’s surface, and take them as far out as about 19,420 miles (31,250 kilometers), traveling through diverse areas of the belts. By comparing observations from both spacecraft, scientists can distinguish between events that occur simultaneously throughout the belts, those that happen at only a single point in space, and those that move from one point to another over time.
Watch the video above to learn more about the Van Allen Probes and a discovery they made shortly after starting their mission. Credit: NASA Goddard
The Van Allen Probes carry on the work begun by Explorer 1 and, like all successful space missions, are providing answers as well as provoking more questions. NASA continues to explore Earth and space using spacecraft launched aboard a variety of rockets designed to place these observatories in just the right spots to return data that will answer and inspire questions for years to come.
Teach It
- *NEW* Build a Satellite (Grades 5-8) – Students will use the engineering design process to design, build, test and improve a model satellite intended to investigate the surface of a planet.
- Rocket Lessons and Activities (Grades K-9) – Use these exciting lessons to help your students experience the thrill of building their own rockets using the engineering design process!
- Earth Science Lessons and Activities (Grades K-12) – Use these lessons to engage your students in studying Earth from space!
- Build Your Own Space Mission – Have younger students play this game to place instruments aboard a spacecraft and launch it into space!
- Download the GLOBE Observer app and have students be citizen scientists in support of NASA Earth science missions! Learn more about how to participate.
Explore More
TAGS: Explorer 1, STEM, NASA in the Classroom, Lessons, Activities, Teachable Moments
Teachable Moments | November 15, 2017
What’s a Supermoon and Just How Super Is It?
The term “supermoon” has been popping up a lot in the news and on social media over the past few years. But what are supermoons, why do they occur and how can they be used as an educational tool. Plus, are they really that super?
There’s a good chance you’ll hear even more about supermoons in the new year. There will be two supermoons in a row in January 2018! Now is a great time to learn about these celestial events and get students exploring more about Earth’s only natural satellite.
Lessons About the Moon
Explore our collection of standards-aligned lessons for grades 1-12.
How it Works
As the Moon orbits Earth, it goes through phases, which are determined by its position relative to Earth and the Sun. When the Moon lines up on the opposite side of Earth from the Sun, we see a full moon. The new moon phase occurs when the Moon and the Sun are lined up on the same side of Earth.
The Moon doesn’t orbit in a perfect circle. Instead, it travels in an ellipse that brings the Moon closer to and farther from Earth in its orbit. The farthest point in this ellipse is called the apogee and is about 405,500 kilometers from Earth on average. Its closest point is the perigee, which is an average distance of about 363,300 kilometers from Earth. During every 27-day orbit around Earth, the Moon reaches both its apogee and perigee.
Full moons can occur at any point along the Moon’s elliptical path, but when a full moon occurs at or near the perigee, it looks slightly larger and brighter than a typical full moon. That’s what the term “supermoon" refers to.
What makes a supermoon super? Watch this short animation to find out. Credit: NASA/JPL-Caltech
Because supermoon is not an official astronomical term, there is no definition about just how close to perigee the full moon has to be in order to be called “super." Generally, supermoon is used to refer to a full moon 90 percent or closer to perigee. (When the term supermoon was originally coined, it was also used to describe a new moon in the same position, but since the new moon isn’t easily visible from Earth, it’s rarely used in that context anymore.)
A more accurate and scientific term is “perigee syzygy.” Syzygy is the alignment of three celestial bodies, in this case the Sun, Moon and Earth. But that doesn’t quite roll off the tongue as easily as supermoon.
Why It’s Important
Make a Moon Phases Calendar
Use this Moon "decoder wheel" to see where and where to view the Moon all year!
As the largest and brightest object in the night sky, the Moon is a popular focal point for many amateur and professional astronomers pointing their telescopes to the sky, and the source of inspiration for everyone from aspiring space scientists to engineers to artists.
The supermoon is a great opportunity for teachers to connect concepts being taught in the classroom to something students will undoubtedly be hearing about. Students can practice writing skills in a Moon journal, study Moon phases and apply their math skills to observing the supermoon. (Click here for related activities from JPL’s Education Office.)
Incorrect and misleading information about the Moon (and supermoons) can lead to confusion and frustration. It’s important to help students understand what to expect and be able to identify inaccurate info.
What to Expect
Size
As with anything that moves closer to the person viewing it, the supermoon will appear bigger than an average full moon. At its largest, it can appear 14% larger in diameter than the smallest full moon. Keep in mind that a 14% increase in the apparent size of something that can be covered with a fingernail on an outstretched arm won’t seem significantly bigger. Unlike side-by-side comparisons made in science and everyday life, students will not have seen the full moon for at least 30 days, and won’t see another for at least 30 more days. Comparing a supermoon with a typical full moon from memory is very difficult.
While they make for great photographs, images like this one that rely on a special photographic technique aren't an accurate representation of what the supermoon will look like to the naked eye. Credit: NASA/Bill Ingalls | Full image and caption on Flickr
A supermoon looks bigger than a "micromoon" (when the full moon is at apogee) because it's about 40,000 kilometers closer to Earth on average. Credit: NASA/JPL-Caltech
It's nearly impossible to compare the apparent size of the supermoon with a micromoon from memory, but when seen side-by-side as in this graphic, it becomes clear. Credit: NASA/JPL-Caltech
Leading up to a supermoon, there are often misleading images on popular media. A technique that involves using a long telephoto lens to take photographs of the Moon next to buildings or other objects makes the Moon look huge compared with its surroundings. This effect can make for great photographs, but it has nothing to do with the supermoon. In fact, these photos can be taken during any Moon phase, but they will likely be used in stories promoting the supermoon.
There are also images that have been edited to inaccurately dramatize the size of the supermoon. Both of these can lead students, and adults, taking pictures with their cell phone to think that they’ve done something wrong or just aren’t cut out for observing the sky, which isn’t true!
Your students may have noticed that when they see a full moon low on the horizon, it appears huge and then seems to shrink as it rises into the night sky. This can happen during any full moon. Known as the Moon Illusion, it has nothing to do with a supermoon. In fact, scientists still aren’t sure what causes the Moon Illusion.
Brightness
The full moon is bright and the supermoon is even brighter! Sunlight reflecting off the Moon during its full phase is bright enough to cast shadows on the ground. During a supermoon, that brightness can increase up to 30 percent as a result of the Moon being closer to Earth, a phenomenon explained by the inverse square law. (Introduce students to the inverse square law with this space-related math lesson for 6th- through 8th-graders.) As with the size of the Moon, students may not remember just how bright the last full moon was or easily be able to compare it. Powerful city lights can also diminish how bright a supermoon seems. Viewing it away from bright overhead street lights or outside the city can help viewers appreciate the increase in brightness.
What Not to Expect
A supermoon will not cause extreme flooding, earthquakes, fires, volcanic eruptions, severe weather, nor tsunamis, despite what incorrect and non-scientific speculators might suggest. Encourage your students to be good scientists and research this for themselves.
Teach It
The excitement and buzz surrounding a supermoon is a great opportunity to teach a variety of Moon topics with these lessons from JPL’s Education Office:
- *NEW* Observing the Moon (Grades K-6) – Students identify the Moon’s location in the sky and record their observations over the course of the moon-phase cycle in a journal.
- *NEW* Measuring the Supermoon (Grades 5-12) – Students take measurements of the Moon during its full phase over multiple Moon cycles to compare and contrast results.
- *NEW* Moon Phases Calendar and Calculator – Like a decoder wheel for the Moon, this calendar will show you where and when to see the Moon and every moon phase throughout the year!
- *NEW* Look at the Moon! Journaling Project – Draw what you see in a Moon Journal and see if you can predict the moon phase that comes next.
- Moon Phases (Grades 1-6) – Students learn about the phases of the Moon by acting them out. In 30 minutes, they will act out one complete Moon cycle.
- Whip Up a Moon-Like Crater (Grades 1-6) – Whip up a Moon-like crater with baking ingredients as a demonstration for students.
- Modeling the Earth-Moon System (Grades 6-8) – Using an assortment of playground and toy balls, students will measure diameter, calculate distance and scale, and build a model of the Earth-Moon system.
Explore More
- Learn more about the Moon on NASA's Moon website.
For the record: This story originally stated a supermoon would be visible in January and February 2018. The two supermoons of 2018 are both in January.
TAGS: Supermoon, Moon Phases, Moon, Earth's Moon, What's Up, Astronomy, K-12, Educators
Teachable Moments | October 3, 2017
Modeling Gravitational Waves
Update – Oct. 3, 2017: Researchers Kip Thorne and Barry Barish of Caltech and Rainer Weiss of MIT have been awarded the 2017 Nobel Prize in Physics for their “decisive contributions to the LIGO detector and the observation of gravitational waves.”
Thorne, Barish and Weiss played key roles in making the LIGO project a reality through their research, leadership and development of technology to detect gravitational waves.
In a statement to Caltech, Thorne said the prize also belongs to the more than 1,000 scientists and engineers around the world who play a part on LIGO, the result of a long-term partnership between Caltech, MIT and the National Science Foundation.
› Read the Caltech press release
This story was originally published on March 23, 2016.
In the News
A century ago, Albert Einstein theorized that when objects move through space they create waves in spacetime around them. These gravitational waves move outward, like ripples from a stone moving across the surface of a pond. Little did he know that 1.3 billion years earlier, two massive black holes collided. The collision released massive amounts of energy in a fraction of a second (about 50 times as much as all of the energy in the visible universe) and sent gravitational waves in all directions. On September 14, 2015 those waves reached Earth and were detected by researchers at the Laser Interferometer Gravitational-Wave Observatory (LIGO).
Why It's Important
Einstein published the Theory of General Relativity in 1915. In it, he predicted the existence of gravitational waves, which had never been directly detected until now. In 1974, physicists discovered that two neutron stars orbiting each other were getting closer in a way that matched Einstein’s predictions. But it wasn’t until 2015, when LIGO’s instruments were upgraded and became more sensitive, that they were able to detect the presence of actual gravitational waves, confirming the last important piece of Einstein’s theory.
It's also important because gravitational waves carry information about their inception and about the fundamental properties of gravity that can’t be seen through observations of the electromagnetic spectrum. Thanks to LIGO’s discovery, a new field of science has been born: gravitational wave astronomy.
How They Did It
LIGO consists of facilities in Washington and Louisiana. Each observatory uses a laser beam that is split and sent down 2.5-mile (4-kilometer) long tubes. The laser beams precisely indicate the distance between mirrors placed at the ends of each tube. When a gravitational wave passes by, the mirrors move a tiny amount, which changes the distance between them. LIGO is so sensitive that it can detect a change smaller than 1/10,000 the width of a proton (10-19 meter). Having two observatories placed a great distance apart allows researchers to approximate the direction the waves are coming from and confirm that the signal is coming from space rather than something nearby (such as a heavy truck or an earthquake).
Teach It
Creating a model that demonstrates gravitational waves traveling through spacetime is as simple as making a gelatin universe!
Middle school students can develop a model that shows gravitational waves traveling through spacetime while working toward the following Next Generation Science Standard:
- MS-PS4-2 - Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials.
Explore More
- Gravitational waves news, videos and resources
- Laser Interferometer Gravitational-Wave Observatory (LIGO) Website
TAGS: Gravitational Waves, Teachable Moment, LIGO, Black Holes, Einstein
Teachable Moments | September 12, 2017
A Moment You Won't Want to Miss: Cassini's Mission Finale at Saturn
Update – Sept. 11, 2017: This feature (originally published on April 25, 2017) has been updated to reflect Cassini's current mission status, as well as new lessons and activities.
- Visit the Cassini website's Grand Finale Toolkit for a timeline, resources and more information about the final phase of the mission.
- Follow along with NASA via live stream during the Grand Finale on September 15 and in the days leading up to the event. Programming begins on September 13 at 10 a.m. PDT.
- Get the latest news and updates for the Cassini mission on the JPL News website.
- Explore these standards-aligned lessons and out-of-school activities to bring the wonder of NASA's Cassini mission and science at Saturn to students.
In the News
After almost 20 years in space, NASA's Cassini spacecraft has begun the final chapter of its remarkable story of exploration. This last phase of the mission has delivered unprecedented views of Saturn and taken Cassini where no spacecraft has been before – all the way between the planet and its rings. On Friday, Sept. 15 Cassini will perform its Grand Finale: a farewell dive into Saturn’s atmosphere to protect the environments of Saturn’s moons, including the potentially habitable Enceladus.
Lessons All About Saturn
Explore our collection of standards-aligned lessons about NASA's Cassini mission.
How It Works
On April 22, Cassini flew within 608 miles (979 km) of Saturn’s giant moon Titan, using the moon’s gravity to place the spacecraft on its path for the ring-gap orbits. Without this gravity assist from Titan, the daring, science-rich mission ending would not be possible.
Cassini is almost out of the propellant that fuels its main engine, which is used to make large course adjustments. A course adjustment requires energy. Because the spacecraft does not have enough rocket fuel on board, Cassini engineers have used an external energy source to set the spacecraft on its new trajectory: the gravity of Saturn’s moon Titan. (The engineers have often used Titan to make major shifts in Cassini’s flight plan.)
Titan is a massive moon and thus has a significant amount of gravity. As Cassini comes near Titan, the spacecraft is affected by this gravity – and can use it to its advantage. Often referred to as a “slingshot maneuver,” a gravity assist is a powerful tool, which uses the gravity of another body to speed up, slow down or otherwise alter the orbital path of a spacecraft.
In this installment of the "Crazy Engineering" video series from NASA's Jet Propulsion Laboratory, host Mike Meacham talks to a Cassini engineer about astrodynamics and how it was used to design the Saturn mission's Grand Finale.
When Cassini passed close by Titan on April 22, the moon’s gravity pulled strongly on the spacecraft. The flyby gave Cassini a change in velocity of about 1,800 mph (800 meters per second) that sent the spacecraft into its first of the ring-gap orbits on April 23. On April 26, Cassini made its first of 22 daring plunges between the planet and its mighty rings.
This graphic illustrates Cassini's trajectory, or flight path, during the final two phases of its mission. The 20 Ring-Grazing Orbits that Cassini made between November and April 2017 are shown in gray; the 22 Grand Finale Orbits are shown in blue. The final partial orbit is colored orange. + Enlarge image
Clouds on Saturn take on the appearance of strokes from a cosmic brush thanks to the wavy way that fluids interact in Saturn's atmosphere. This images used in this false-color view were taken with the Cassini spacecraft narrow-angle camera on May 18, 2017. Image credit: NASA-JPL/Caltech/SSI | › Full image and caption
This animated image of Saturn's moon Enceladus is a composite of six images taken by the Cassini spacecraft on Aug. 1, 2017. Image credit: NASA-JPL/Caltech/SSI | › Full image and caption
These are the highest-resolution color images of any part of Saturn's rings, to date, showing a portion of the inner-central part of the planet's B Ring. The view is a mosaic of two images that show a region that lies between 61,300 and 65,600 miles (98,600 and 105,500 kilometers) from Saturn's center. Image credit: NASA-JPL/Caltech/SSI | › Full image and caption
As Kepler’s third law indicates, Cassini traveled faster than ever before during these final smaller orbits. Cassini's orbit continued to cross the orbit of Titan during these ring-gap orbits. And every couple of orbits, Titan passed near enough to give the spacecraft a nudge. One last nudge occured on September 11, placing the spacecraft on its final, half-orbit, impact trajectory toward Saturn.
Because a few hardy microbes from Earth might have survived onboard Cassini all these years, NASA has chosen to safely dispose of the spacecraft in the atmosphere of Saturn to avoid the possibility of Cassini someday colliding with and contaminating moons such as Enceladus and Titan that may hold the potential for life. Cassini will continue to send back science measurements as long as it is able to transmit during its final dive into Saturn.
Why It’s Important
Flying closer than ever before to Saturn and its rings has provided an unprecedented opportunity for science. During these orbits, Cassini’s cameras have captured ultra-close images of the planet’s clouds and the mysterious north polar hexagon, helping us to learn more about Saturn’s atmosphere and turbulent storms.
The cameras have been taking high-resolution images of the rings, and to improve our knowledge of how much material is in the rings, Cassini has also been conducting gravitational measurements. Cassini's particle detectors have sampled icy ring particles being funneled into the atmosphere by Saturn's magnetic field. Data and images from these observations are helping bring us closer to understanding the origins of Saturn’s massive ring system.
Cassini has also been making detailed maps of Saturn's gravity and magnetic fields to reveal how the planet is structured internally, which could help solve the great mystery of just how fast Saturn is rotating.
On its first pass through the unexplored 1,500-mile-wide (2,400-kilometer) space between the rings and the planet, Cassini was oriented so that its high-gain antenna faced forward, shielding the delicate scientific instruments from potential impacts by ring particles. After this first ring crossing informed scientists about the low number of particles at that particular point in the gap, the spacecraft was oriented differently for the next four orbits, providing the science instruments unique observing angles. For ring crossings 6, 7 and 12, the spacecraft was again oriented so that its high-gain antenna faced forward.
Fittingly, Cassini's final moments will be spent doing what it does best, returning data on never-before-observed regions of the Saturnian system. On September 15, just hours before Cassini enters Saturn's atmosphere for its Grand Finale dive, it will collect and transmit its final images back to Earth. During its fateful dive, Cassini will be sending home new data in real time informing us about Saturn’s atmospheric composition. It's our last chance to gather intimate data about Saturn and its rings – until another spacecraft journeys to this distant planet.
Explore the many discoveries made by Cassini and the story of the mission on the Cassini website.
Teach It
Use these standards-aligned lessons to get your students excited about the science we have learned and have yet to learn about the Saturnian system.
- NEW! Activity Collection: Jewel of the Solar System – Explore Saturn and the Cassini mission with this eight-part series of activities targeting after-school settings.
- Jewel of the Solar System Activity Guide
- What Do I See When I Picture Saturn?
- Where Are We in the Solar System?
- Discovering Saturn: The Real "Lord of the Rings"
- Saturn's Fascinating Features
- My Spacecraft to Saturn
- All About Titan and Huygens Probe
- Drop Zone! Design and Test a Probe
- Celebrating Saturn and Cassini
- Lesson: Flying By Saturn's Moon Enceladus – Teach students about Saturn's scientifically intriguing moon Enceladus and investigate its fascinating features, including its ocean and plumes, using math.
- Video Lesson: Bouncing Radio Waves Off Titan's Lakes – Learn about one way we study Titan in this educational video.
- Problem Set: Pi in the Sky – Have older students use mathematics to calculate Cassini's fuel reserves.
- Problem Set: Pi in the Sky 4 – Students can also calculate the date of the spacecraft's Grand Finale dive into Saturn.
- Download a poster of Saturn and the Cassini mission timeline.
- Download these Cassini retro posters.
Explore More
- Cassini Lessons for Educators
- Cassini Activities for Students
- Cassini Mission Website
- Cassini Grand Finale Toolkit
- Cassini Mission Overview
- Interactive Cassini Mission Timeline
- Video: NASA VR: Cassini's Grand Finale (360 Video)
- Slideshow for Students (includes a free poster!): 8 Real World Space Facts About Saturn's Moon Enceladus
- Slideshow for Students (includes a free poster!): Ocean Worlds
- Explore the Cassini Spacecraft in 3-D
- The Saturn System Through the Eyes of Cassini (e-book)
TAGS: Saturn, Titan, Cassini, Grand Finale, Teachable Moments, Kepler's Laws, K-12, Lessons,