Asteroid last weekend.
The robots took small jumps, making it the first time it has ever been asteroid.
The two machines, called rovers, landed on the asteroid Ryugu on September 21. The Japan Space Exploration Agency says they were lowered to the surface by an unmanned spacecraft called the Hayabusa2.
Asteroids are small, rocky objects orbiting around the sun. They have been described as minor planets.
The Japanese spacecraft first arrived at Ryugu last June. It flew as close as 55 meters to the asteroid before it releases the rovers. Hayabusa2  The next day, Japan's space agency, known as JAXA, has released some pictures of the rovers. Japan shows the surface of the asteroid's surface.
JAXA project manager Yuichi Tsuda arrived in a statement after the robots arrived.
The rovers are named MINERVA-II 1a and 1b. They are about the size of a can cookies . Their movements are powered by solar energy from the sun.
They will continue to move across the surface, taking pictures and collecting information about temperature.
Why larger asteroids?
A large rover and lander wants to be released onto the surface from Hayabusa2 in the coming months.
You may be wondering why send a spacecraft millions of miles away to land on an ancient piece of rock traveling through space? Scientists believe that asteroids may provide information about the earliest days of our solar system, some 4 billion years.
Ryugu orbits the Sun between Earth and Mars, and is a C-type asteroid-the most common type of asteroid in our solar system. Scientists believe some asteroids may contain organic matter and water.
JAXA hopes to find out just what they are doing. [Ryugu may give researchers a look at the beginning of life.]
Hyabusa2 is set to try three letter landings on Ryugu to collect rock samples . The first attempt is to be released in October.
Later this week, the spacecraft is set to release another lander onto the asteroid. The device is a project of the German and French space agencies. Known as MASCOT, it wants to carry four surveillance devices. The spacecraft will release a larger rover, called Minerva-II-2, in 2019.
Hyabusa2 wants to stay at Ryugu until late next year. Then it wants to fly back to earth with the asteroid samples. JAXA expects the spacecraft to return home by 2020.
Scientists want to study the samples to understand more about how planets were formed around the Sun in the early days of our solar system.
In time, these samples will be compared to ones the American space agency NASA hopes to get from the asteroid Bennu. NASA's spacecraft was launched two years ago. Bennu in early December.
NASA's spacecraft wants to take samples from the asteroid in 2020, and three years later they return to Earth for scientists to study.
I'm Anne Ball.  Anne Ball wrote this story for VOA Learning English with information from The Associated Press. George Grow was the editor.
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Words in This Story
asteroid – n . any one of thousands of small planets that circle around the sun
cookie – n.
organic – adj. a sweet baked food that is usually small, flat, and made from flour and sugar
sample – n. a small amount of something that gives you information about the thing it was taken from