The American space agency NASA says its Mars explorer, or rover, has successfully collected its first Martian rock sample. The rover, called Perseverance, used a drill attached to its robotic arm to remove a small, circular sample -- also called a core -- from a larger rock on the surface of Mars. NASA confirmed the successful collection in a statement on Monday. The agency also released pictures of the sample, which it said appears to be about as thick as a writing instrument. After the drilling was completed, Perseverance took additional pictures of the sample as well as the tube it was kept in. The images are useful to scientists back on Earth who study the sample. In the final step, Perseverance moved the tube to a storage area inside the rover and hermetically sealed the container. Hermetic sealing is a process that completely closes off the container so that no air can flow in or out. The Perseverance team shared the news on Twitter. “It’s official: I’ve now captured, sealed, and stored the first core sample ever drilled on another planet, in a quest to return samples to Earth.” The tweet added that the sample was “the first in a one-of-a-kind Martian rock collection