China’s Yutu-2 lunar rover has beamed back more images of the “colored mysterious substance” it discovered in a small crater on the dark side of the moon, which has captivated the scientific community since July.

The team behind China’s Chang’e-4 mission, which operates the Yutu-2 rover, claimed the unusual “gel-like” material’s “shape and color is significantly different from the surrounding lunar soil” after Yutu-2’s second pass by the crater in August (the first examination was deemed unsatisfactory as there were too many shadows in the images).

The latest images were taken by the rover’s obstacle-avoidance camera as it carefully approached the seven-foot-wide (two-meter) crater, the source of the unusual substance.

The red and green tinges in the image are as a result of the instrument used, a Visible and Near-Infrared Spectrometer (VNIS), which detects light as it is scattered or reflected off materials to reveal their chemical makeup, as opposed to the color emanating from the substance itself.

Though the second pass was carried out in August, the results were not released until this week.

While it’s too early to tell exactly what the substance is, researchers like Clive Neal, a lunar scientist at the University of Notre Dame, speculate that the substance could be fragments of minerals cemented together to form black shiny glass as a result of high-speed impacts on the lunar surface, which would make sense, given that the substance is located in a crater.

So far, Yutu-2 has traveled some 934 feet (285 meters) since touching down on the far side of the moon on January 2. The Chinese mission completed its ninth lunar day on September 5. Lunar day 10 will begin around September 22 for Yutu-2 and the following day for the lander. A lunar day lasts roughly two weeks.