By the Sankei Shimbun
The whereabouts of Ryugu Castle is one of the well-entrenched mysteries of Japanese mythology. The castle is mentioned in the story “Urashima Taro,” which is detailed in Otogi-zoshi, a collection of literature written during the Muromachi Period (17th–18th century).
According to this story, the castle was located off the shores of Tango Province, which is now part of Kyoto Prefecture. Urashima Taro rescues a turtle, which transforms into a beautiful wife and brings him on a journey “which would take about ten days by boat.”
The asteroid Ryugu is named after this mysterious castle. Located about 300 million kilometers away from earth, it is far out in the universe.
The explorer Hayabusa2 left Earth three and a half years ago on its own journey in search of Ryugu, finally arriving safely on June 27—after traveling 3.2 billion kilometers while orbiting the sun.
In mythology, Urashima Taro lives happily in Ryugu castle with his wife for three years. Hayabusa2 will stay at its own Ryugu for a year and a half, during which time it will attempt a total of three landings on the asteroid. The space exploration vehicle will collect mineral samples from the surface and deeper, and should return to Earth around the end of 2020.
The explorer Hayabusa2 is a successor to the discovery vehicle Hayabusa, which gathered samples from asteroid Itokawa and returned to Earth in 2010. Itokawa is an asteroid made entirely of rocks, while Ryugu, it is believed, contains organic matter and minerals, including water—the ingredients for life.
How did our blue planet get its water in the first place?
I explained in a column I wrote in Sankei in May 4 (only in Japanese) that the leading theory is that an asteroid from distant space brought water to Earth. The mineral samples from Ryugu may verify this theory.
In fact, some propose that Urashima Taro’s journey to Ryugu Castle was actually space travel, because hundreds of years had passed by the time he came back home. Proponents argue that this can be explained by Einstein’s theory that time slows down inside an extremely fast rocket.
At the end of the story in the myth, Urashima Taro goes home with a tamatebako (jeweled box) he had received as a souvenir. Upon opening the box, he instantaneously becomes a very old man.
Now, with great anticipation, we wait for Hayabusa2 to bring us its own tamatebako. After all, the tamatebako from asteroid Ryugu may contain clues to solving the origin of life on earth.
Click here to read the original article in Japanese.