By Stacy Palen

Summary: Hayabusa2 has been investigating the asteroid Ryugu. This is a sample-return mission, which has implications for Solar System formation and may cast light on the origins of life on Earth.

Article: Japan (Very Carefully) Drops Elastic Explosives Onto an Asteroid

1. Consider what you know about the origin of the Solar System. What are astronomers hoping to learn from Hayabusa2’s mission to Ryugu?

Answer: They are hoping to learn about the composition of matter in the Solar System when it formed. This could confirm or refute our ideas about Solar System formation and the formation of the asteroid belt. The precursor molecules for life are also present on the asteroid, which may give us clues about the origins of life on Earth.

2. The article states that Hayabusa2 “physically touched down” on Ryugu in February 2019, and took a sample of dust kicked up. Go online and read more about it. Describe this event in more detail. Do you consider “physically touched down” to be an accurate characterization of what happened?

Answer: The spacecraft approached the surface and shot a small projectile into the asteroid. A sampler horn collected the kicked up dust and the spacecraft moved on. This is not quite what’s implied by the summary sentence in the news article.

3. Ryugu is less than a mile across, in an orbit between Earth and Mars. Using an average orbital radius between those two planets (1.25 AU), find the orbital period of Ryugu. Convert this orbital period to seconds.

Answer: This is a review of Kepler’s third law. The period is 1.16 years, which equals 3.7 X 10⁷ seconds.

4. The circumference of Ryugu’s orbit is 1.2 X 10¹² Divide this distance traveled by the period to find the speed of the asteroid in its orbit. This is the speed that Hyabusu2 must be traveling in order to rendezvous with the asteroid.

Answer: This is a reminder of the definition of the properties of an orbit (what is the circumference, and what is the period). The speed is 32,000 m/s.

5. When was the spacecraft launched, and when is the sample return mission expected to arrive back here on Earth?

Answer: The spacecraft launched in December 2014, and will return a capsule to Earth in December 2020.

Image Contributor: Mark Garlick/Science Photo Library, 1 March 2013