Shortly after Japan’s Hayabusa2 probe returned to Earth, JAXA showed off some of the samples it collected from asteroid Ryugu. Those rocks came from the “A” chamber of the probe’s sample capsule, which means they were collected during the mission’s first touchdown in February 2019. Now, JAXA has released photos showing the contents of the capsule’s “C” chamber, which it opened on December 21st.

In JAXA’s tweet, it said the agency opened both chambers “B” and “C.” The “B” chamber is empty since it wasn’t used for collection, but the “C” chamber was used to collect samples during Hayabusa2’s second touchdown in July 2019. JAXA fired an explosive into the asteroid before the second touchdown to create a crater and be able to gather samples from deeper underground. Scientists are hoping that the subsurface samples can offer more clues about the solar system’s formation and early period, since they hadn’t been exposed to the harsh environment of space.

JAXA says the largest particles in chamber “C” were about a centimeter in size. If you take a look at the photos, the agency marked one of the particles as “???” or “artificial object.” It has yet to confirm where that object came from, but JAXA believes it could be “aluminum separated from the sampler horn” when it used an explosive on asteroid Ryugu’s surface.