SPACE — China's Chang'e 4 mission has found an unusually colored gel-like substance on the far side of the moon.

Space.com reports that on July 28, the Yutu-2 lunar rover had been exploring the far side of the moon. While reviewing the rover's images, a Chang'e 4 team member noticed that one crater seemed to contain a material distinct from the rest of the lunar surface.

The Yutu-2 was directed to approach the crater and examine its inside with its Visible and Near-Infrared Spectrometer.

Mission scientists have not revealed what the substance is, describing it only as gel-like and with an unusual color.

Outside researchers have suggested that one possible explanation is that the substance is melted glass created from meteorites striking the surface of the moon.

China's Chang'e 4 spacecraft successfully made the first-ever soft landing on the far side of the moon on January 3. The Yutu-2 rover is now on its ninth lunar day, with each day equivalent to two Earth weeks.

In May, Chinese scientists also announced that they'd found evidence of material from the lunar mantle in the regolith of the moon's Von Karman crater.