Odd One Out

Space objects

Activity overview

15 mins
Ages 9 – 11

Science topics:


Put your class’ observation skills to the test with these three objects found in space. This activity is great for promoting observation and discussion skills.

Run the activity

1. Show the three images above and ask everyone to come up with as many similarities and differences as they can. If they get stuck, prompt them to think about:

  • appearance
  • what they do
  • where they might be found

2. Then, everyone needs to decide which one is the odd one out and why. Encourage a reason for every answer and there is no wrong answer!

Background science

Background science 

The objects are the International Space Station (ISS), the Moon, and a comet. The ISS is the size of a football pitch and over 240 people from 17 countries have visited it since 2000. It is an artificial satellite which orbits the Earth. There's more information on the ISS for children on Nasa's website.  

The comet was visited by the European Space Agency's Rosetta mission in 2014. Comets are pieces of dust and ice left over from when the solar system formed. When a comet gets closer to the Sun it warms up and emits gases that produce a visible atmosphere and sometimes a fiery tail. 

The Moon is Earth's natural satellite and it orbits the Earth once approximately every 28 days (a lunar month). The Moon has been visited by only 12 humans between 1969 and 1972 but there are plans by NASA and the European Space Agency for astronauts to return during this decade. The Moon rotates in synchrony with the Earth which is why we only ever see the same side of the Moon. 


Watch out for 

Some children may believe that the Moon appears to change shape because clouds move in front of it, rather than as a result of light from the Sun falling on different regions of it. Some can also think that its shape changes several times in one night. 

Children can believe that the Moon is moving across the night sky, rather than understanding that the Earth is spinning which affects where we see the Moon. Children often don’t think you can see the Moon in the sky during the day – it only comes out at night. It is bright enough to be seen during the day, but only just, and it is so faint that many people do not notice it.   

For a detailed guide to children’s misconceptions and a guide to questions to assess prior knowledge look at these BEST resources.    

Take it further

STEM  has a huge range of primary science teaching ideas based on the ISS and Rosetta mission, while the Royal Observatory Greenwich has some great resources on the phases of the Moon!

If you're doing a topic on space or rockets, check out the Astro Science Challenge. It's free, features Tim Peake and is designed to support English and maths too!  

Linked Explorify activities- our recommendations: 

Try more of our Moon activities: Black hole, Have you ever looked at the Moon and noticed how it appears to be different shapes at different times? 


Watch this useful video which explains why satellites don’t fall out of the sky. In this ESA film, Paxi finds out more about the Rosetta mission and comets. 

Image credit:

NASA via European Space Agency CC BY-NC

NASA via Goddard Space Flight Center CC BY-NC