Compare the planets, and where liquid water could exist

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   A rocky planet orbits inside its star's habitable zone. What should Esme conclude?

   • Life is known to be there
   • It must look just like Earth, with blue oceans and white clouds
   • Liquid water could exist, so it is a good target to study
   • Its star is like the Sun
2. 2.

   Habitable-zone distance grows as √brightness; star 9 times as bright; planet at 1 AU. A planet sits at 1 AU from a star 9 times as bright as the Sun. Is it at that star's habitable-zone distance, by Jun's math?

   • Yes: brighter stars have closer zones
   • No: the zone is near 9 AU
   • Yes: 1 AU works for any star
   • No: the zone is near 3 AU, so 1 AU is too hot
3. 3.

   Luz's friend says any planet in a habitable zone must have life. Which response is best (NASA)?

   • Disagree: it means liquid water could exist, not that life does
   • Disagree: habitable zones have no water
   • Agree: NASA has already found living things on planets in such zones
   • Agree: water brings life

4. Read this first

   Planets (NASA Planetary Fact Sheet)

   Planet	Distance (million km)	Mean temperature (°C)	Density (kg/m³)
   Mercury	57.9	167	5,429
   Venus	108.2	464	5,243
   Earth	149.6	15	5,514
   Mars	228.0	−65	3,934
   Jupiter	778.5	−110	1,326
   Saturn	1,432.0	−140	687

5. 4.

   Milo's cousin says the closest planet to a star is always the hottest. Which response is best (NASA)?

   • Agree: Mercury, nearest the Sun, must be the hottest planet there is
   • Agree: distance alone sets temperature
   • Disagree: Venus is hotter than Mercury because its air traps heat
   • Disagree: the farthest planets are hottest
6. 5.

   Noah's friend says every star's habitable zone sits at Earth's distance, 1 AU. Which response is best?

   • Agree: Earth sets the rule
   • Disagree: the zone moves out for bright stars and in for dim ones
   • Disagree: brighter stars have closer zones
   • Agree: 1 AU is right for any star
7. 6.

   Four planet cards, labeled A to D. Which planet is the best target for studying possible liquid water, by Ren's reading?

   • A gas giant inside the zone
   • A rocky planet far outside the zone
   • A rocky planet where life was already found and studied
   • A rocky planet inside its star's habitable zone
8. 7.

   Dip = (planet diameter ÷ star diameter)²; dips 1% and 4%. Two stars show transit dips of 1% and 4%, and both stars are the same size. How do the planets' diameters compare, by Tala's math?

   • The second is 4 times as wide
   • The second is 16 times as wide
   • They are the same width
   • The second is twice as wide

9. Planets (NASA Planetary Fact Sheet)

   Planet	Distance (million km)	Mean temperature (°C)	Density (kg/m³)
   Mercury	57.9	167	5,429
   Venus	108.2	464	5,243
   Earth	149.6	15	5,514
   Mars	228.0	−65	3,934
   Jupiter	778.5	−110	1,326
   Saturn	1,432.0	−140	687

10. 8.

    Mars (−65 °C, thin air) and Earth (15 °C) both lie near the Sun's habitable zone. What best explains Mars's cold surface, by Zee's reading?

    • It is closer to the Sun than Earth, so its air is colder
    • It is farther out, and its thin air traps little heat
    • It is a gas giant
    • It is in a different star's zone
11. 9.

    More than 6,000 exoplanets are confirmed (NASA). Why are Earth-sized planets in wide orbits around Sun-like stars still rare in the list, by Ari's reading?

    • They are much harder to detect
    • Sun-like stars have no habitable zone
    • Transits of small planets are the deepest
    • They do not exist
12. 10.

    Four data cards, labeled A to D. Which data would help Bo judge whether a planet could hold liquid water?

    • Its distance, its star's brightness and its atmosphere
    • Just the planet's color
    • Whether life has been seen
    • Just its distance, since distance alone sets temperature