Directions: After students read the article “Kuiper belt dust may be sprinkled in our atmosphere,” have them answer the questions below.

1. Based on the text of the article, where is the Kuiper Belt? Can you infer any additional information about the Kuiper Belt’s location from the image that accompanies the article?

The Kuiper Belt is located beyond Neptune’s orbit. The image suggests that the Kuiper Belt rings our solar system and passes through Pluto’s orbit.

2. What evidence from the Kuiper Belt do scientists think they have found here at Earth?

Scientists think that some grains of dust collected from Earth’s stratosphere might have originated from the Kuiper Belt.

3. How do scientists try to determine the original home of a dust grain from space?

Grains of space dust have microscopic tracks where heavy charged particles from solar flares have punched through. More tracks suggest that a grain has wandered through space for longer and thus probably originated farther from Earth.

4. What other object from space did scientists use in the study? What data were known that made the object useful and why?

A moon rock collected during one of the Apollo missions provided a sample with a known age and known track density, allowing scientists to have a reference measurement of how many tracks a typical grain picks up per year.

5. Name at least two scientific tools mentioned in the article and explain what they were used for.

Scientists have used balloons and aircraft to collect dust samples from the stratosphere.

Scientists used an electron microscope to look for microscopic tracks in dust grains from space.

6. Why do the scientists’ measurements of the rate at which dust grains pick up tracks differ from previous measurements? How do the old and new rate compare?

The last track rate measurements were made in 1975 with instruments that are less precise than today’s instruments. The new rate is about one-twentieth of the old rate.

7. Name one large and one small measurement given in the article. Explain what these are measurements of, and why they are so different in scale.

One possible student response: 10 million years is the approximate amount of time it would take for space dust from the Kuiper Belt to reach Earth. The amount of time is so large because the Kuiper Belt is so far from Earth.

A few tens of micrometers is the approximate width of some dust grains from space. These dust particles are microscopic.

8. Why do you think this article has the label “RETHINK”?

Scientists had thought that some dust particles in Earth’s stratosphere came from comets and asteroids between Jupiter’s orbit and the sun, but it now appears that a portion of that dust may have come from the more-distant Kuiper Belt. Scientists are rethinking their understanding of the source of this dust.