Hosting Center(s)
  • Glenn Research Center
Subject Category
  • Earth Science
Unit Correlation
  • Exploring Space
Grade Level
  • K-04
  • 05-08
  • 09-12
Minimum Delivery Time
  • 030 min(s)
Maximum Connection Time
  • 060 min(s)

Event Focus

There are more than a 6,000 near-earth asteroids (NEAs) with a diameter larger than 50 meters. Asteroids of this size can penetrate our atmosphere. Of these there are 1,106 known potentially hazardous asteroids (PHAs) which have the possibility of making a close Earth approach. Because of popular movies and television programs, many people expect the earth to be hit by killer asteroids. What potential danger do they really pose, and is there anything we can do to avoid or prevent contact?



This module is appropriate for video conference AND web conference presentation.

Asteroids present a mysterious, ancient, and potentially Earth-damaging threat within our Solar System. Many formed during the beginnings of our Solar System, 4.5 billion years ago, and some of them have very different, and sometimes eccentric, egg-shaped orbits. Occasionally their paths do cross the Earth's orbit, and at times they enter the atmosphere where they either burn up as meterors or land as meteorites. Asteroids have created large features on the Earth, such as craters and water basins. This modules helps students learn about NASA missions to study asteroids so they can gauge for themselves the threat of future asteroid collisions.


Instructional Objectives




Learners will describe what they know about asteroids and what kind of a threat they think might pose.



Learners will investigate the size, number, location, and composition of asteroids as well as evidence of past strikes on earth.


Learners will discover why asteroids may become a threat to earth



Learners will expand their knowledge by considering several cases of close asteroid encounters as well as future predictions



Learners will evaluate their learning by looking at ways to avoid encounters with asteroids.


Sequence of Events


Pre-Conference Activities


Edible Asteroids is a fun and interesting way to introduce the topic of asteroid study.


Ask students what questions they have about asteroids. If needed or available, read a story, provide an article or show a movie clip to encourage more student questions. Post the questions so they can be addressed before, during, and after the videoconference.




Asteroid: any of the several million small solar-system bodies of from 480 miles (775 km) to 50 meters in diameter that revolve about the sun in orbits lying mostly between those of Mars and Jupiter. They are also called minor planets and planetoids.

Asteroid Belt: a region of space lying between the orbits of Mars and Jupiter in which almost all of the asteroids in the solar system orbit.

AU: an astronomical unit equal to the average distance from the earth to the sun, about 93 million miles. Asteroids less than 1.3 AU at their closest approach to earth are called near earth asteroids.

Orbit: the curved path, usually elliptical, described by an asteroid as it goes around the sun.

NEA: Near Earth Asteroids are asteroids whose orbits bring them within at least 1.3 AU to Earth's orbit. NASA has a congressional mandate to catalog all NEAs that are at least 1 kilometer (0.6 miles) wide.

PHA: A Potentially Hazardous Asteroid is a Near-Earth asteroid with a size and an orbit such that it has a potential to make threatening close approaches to the Earth. An asteroid is considered a PHA if its Minimum Orbit Intersection Distance (MOID) with respect to Earth is less than 0.05 AU and its diameter at least 150 m (nearly 500 ft). This is big enough to cause unprecedented regional devastation for a land impact or the threat of a major tsunami for an ocean impact, if it were to hit the Earth. Such impact events occur on average once per 10,000 years or less.

Satellite: An object that revolves around a larger primary body. All asteroids are satellites of the Sun, and some asteroids have smaller asteroids as their own satellites.


Videoconference Activities


At the beginning of this videoconference, the facilitator will question the students concerning their thoughts about asteroids, their origin,  size, and  role in the solar system. The facilitator will discuss the question, "Do you think asteroids could be a problem to Earth?"  The facilitator will use pictures, drawings, movies, and other graphics to help students develop an understanding about asteroids.

The facilitator will get students thinking about what asteroids are really like. He will help them develop a concept of space through asking questions and using models, movies, and pictures to answer their questions. To build on student's preconceptions, help them extend their ideas, and develop a more accurate picture of asteroids the facilitator may ask questions like the following:

What is an asteroid? Where are they in the solar system? (show images of the solar system and asteroid belt) Do all asteroids orbit in the asteroid belt? Could a spacecraft pass through the asteroid belt without crashing? ( display some incorrect images from science fiction and use analogy of crossing a country road as opposed to running across a freeway) How big are they? Why are they oddly shaped instead of being round like planets? (show images of asteroids take by various space probes) Do they ever come close to earth? Will we ever be hit by an asteroid? (show map of Earth's craters)

The facilitator will use this time to model questioning, thinking through issues, and to praise the students for asking good questions to build their confidence. He will often answer questions with questions, then show models, make diagrams, or show movies. Here are some questions we have heard in other video conferences and the way the facilitator takes the key idea from the student's question and helps them develop an accurate idea.

1) Is an asteroid going to hit the earth? (they have in the past and we can only calculate the odds of it happening again. Show pictures of the 1908 Tunguska incident)

2) Could we live on an asteroid? (even large asteroids don't create much gravity, so it is hard to even land on them. None have an atmosphere and all are barren, cold, and cratered. Show images of asteroids close up)

3) How do we know if an asteroid is going to hit the earth? (first you have to find them in the sky using telescopes which is hard to do because they are small and don't reflect much light. Then you need to track them to determine their orbit to see if they will come close. Show some tracking images)

4) Where did they come from? (most scientists think they are left over from the time that the solar system formed and just are big enough to clump together by gravity to make a planet. Jupiter's gravity pull also keeps this from happening.)

5) Why do some of them come towards Earth instead of staying out in the asteroid belt? (Even though they are very far apart in the asteroid belt, collisions do occur that send them out on different orbit, some of which cross the orbit of earth. Jupiter's gravitational influence also causes some to change their orbits.)

6) If an asteroid hits the earth, will it wipe us out? (It depends on the size of the asteroid and where it lands. Show images of past events and of Meteor crater)

7) What can we do to keep an asteroid from hitting us? (Scientists have ideas, but nothing has ever been tried. Students asked for suggestions and then discuss the pro's and con's of each)

8) Why are they shaped so differently? ( It depends on their o.rigin and mass)

9) Can the space shuttle fly out to an asteroid and destroy it? (The shuttle is only designed to fly in low-earth orbit, no farther than about 300 miles up.)

10) What means do we have to deflect or destroy a dangerous asteroid today? (None. Maybe you could become the scientist or engineer to develop one. Discuss careers)


Post-Conference Activities


Ask students to return to their questions from the pre-conference and work in groups to answer their original questions based on what they have learned. Let them present to each other their ideas, compare them, and compare their sources and ways they learned about their ideas.  Hold a class discussion about Asteroids and their possible impact to our Earth.


Follow the tracking of NEA's via this NASA website. http://neo.jpl.nasa.gov/index.html




Further information about asteroids can be found at the following:


NASA information about asteroids and missions to asteroids can be found at



Take a look at the current NASA missions to the asteroids Vesta and Ceres, DAWN




NSTA Science Content Standards 5-8:





  • Most objects in the solar system are in regular and predictable motion. Those motions explain such phenomena as the day, the year, phases of the moon, and eclipses. Asteroids orbiting in the asteroid belt between Mars and Jupiter will be compared to near-Earth asteroids.





  • Risk analysis on Near Earth Asteroids considers the type of hazard and estimates the number of people that might be exposed and the number likely to suffer consequences based on the size of the asteroid. The results are used to determine the options for reducing or eliminating risks.


NSTA Science Content Standards: 9-12






  • Gravitation is a universal force that each mass exerts on any other mass. The strength of the gravitational attractive force between two masses is proportional to the masses and inversely proportional to the square of the distance between them. A balance between the gravity effect of Jupiter and the Sun keep the asteroids in orbit between Jupiter and Mars.

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Page Last Updated: August 29th, 2014
Page Editor: NASA Administrator