Spacefaring bacteria in the spotlight

This exercise is a part of Educator Guide: Bacteria Can Survive for Years in Space / View Guide

Directions for teachers: After your students read the online Science News article “If bacteria band together, they can survive for years in space,” ask them to answer the following questions. A version of the story, “Bacteria can survive for years in space,” can be found in the September 26, 2020 issue of Science News.    

1. Why is outer space not friendly to most known life-forms?

The extreme conditions of outer space, including temperature, pressure and radiation, could damage an organism’s DNA and kill the organism.

2. What type of bacteria did scientists use in an experiment on the International Space Station? Why did scientists choose to study these bacteria?

Scientists studied Deinococcus. It thrives in extreme environments on Earth and is resistant to radiation damage, making it a good test subject for an outer space experiment.

3. What was the purpose of the experiment? Describe the experimental procedure in your own words.

Scientists wanted to determine how long Deinococcus could survive in outer space, so they sent up dried pellets of the bacteria to the International Space Station. An astronaut attached plates containing the pellets to the exterior of the station, where the pellets were exposed to the harsh environment. Each year, samples were sent back to Earth where scientists rehydrated the samples and monitored them for bacterial growth.  

4. What were the independent and dependent variables of the experiment? Explain how you know.

The independent variable was the pellet thickness and the dependent variable was the survival rate of the bacteria. The scientists varied the size/thickness of the bacteria pellets that were sent to space to see if it affected the bacteria’s rate of survival in space.

5. What were the results of the experiment? Explain.

Deinococcus in pellets that were at least 500 micrometers thick could survive in outer space for up to three years. Bacteria on the outside of the pellets died, but those dead bacteria protected microbes in the pellets’ interiors. About 4 percent of microbes in the pellets survived.       

6. What is the maximum estimated time the bacteria in 1,000-micrometer pellets could survive in outer space, according to the researchers’ estimates?

Eight years.

7. How might bacteria unintentionally end up in outer space, according to the researchers? Can you think of another way bacteria could end up in outer space?

Scientists say clumps of bacteria could be launched into space by meteorite impacts or by storm-induced disturbances in Earth’s magnetic field. Bacteria also might hitch a ride to outer space on the surface of spacecraft. 

8. What implications do the findings have for life elsewhere in the universe?

If clumps of microbes can survive in outer space, they may be able to spread from Earth to other planets or space rocks.

9. Find a word or concept in the story that is new to you. Define it using the context given in the article.

Panspermia is new to me. It is the concept that life can travel throughout the universe, spreading from place to place.

10. What makes the experiment an example of a successful collaboration in science, technology, engineering and math (STEM)?

A scientist designed the experiment and prepared the necessary materials, but had to rely on an astronaut on the space station to conduct part of the experiment. The scientist on Earth and the astronaut had to trust each other to make the collaboration successful.