Clues From Sky and Ground: teacher key

Aliens and UFOs, grade 4 edition, written for 4th grade. To ask if life exists elsewhere, people collect clues: lights in the sky, rivers on Mars and planets around other stars.

Read the book. Print this page for the key.

Questions and answers

1. What is the habitable zone?
   • The area around a star where a planet could have liquid water (answer)
   • The red rust on Mars
   • The place rovers are built
2. What clues show that Mars once had water?
   • River valleys, deltas and lakebeds (answer)
   • Red clouds
   • Moving lights
3. Which can be reported as a UFO?
   • A weather or research balloon (answer)
   • A rover on Mars
   • A telescope
4. Why is Mars red?
   • It is very hot
   • Its ground has rusty iron (answer)
   • It is covered in lakes
5. What do rovers send back from Mars?
   • Pictures and measurements (answer)
   • Tiny Mars creatures
   • Rain
6. What does unidentified mean?
   • Not yet known (answer)
   • Alien
   • Very fast

Words

• exoplanet: far-off planet
• habitable: fit to live
• deltas: river fans
• balloons: floating bags
• unidentified: not yet known