China National Space Administration

China's Yutu-2 rover, launched as part of the Chang'e 4 mission, is the first-ever robot to explore the far side of the moon. Since landing in January, it's snapped gorgeous views of the lunar surface and made one unexpected discovery. Now, it's made another surprising find: an unusual substance with a "gel-like" appearance hidden inside a crater.

According to a report by Space.com, the rover's surprise discovery was made during exploration activities on lunar day 8, which began on July 25. Each lunar day lasts for two Earth weeks and during this time the solar-powered rover carries out scientific observations, measures radiation and surveys its surroundings.

Three days into day 8, a member of the Chang'e 4 team was reviewing images taken during by the rover and noticed a strangely colored material, distinct from the gray soil around it. So, the team instead turned its attention toward the substance and sent the rover towards the crater for a better look. The Yutu-2 "drive diary" says the team commanded the rover to point its spectrometer, a device which can evaluate the composition of materials, towards the unusual substance.

China National Space Administration

The team didn't indicate what the substance might be and they haven't shared an image of the weird material. The team did, however, share an image of the rover heading for the crater to have a gander at what's inside.

I know you're thinking aliens but Andrew Jones, a journalist reporting on the Chinese space program, wrote that one possible explanation is that the gel-like substance is melted glass, created after a meteor strike.

China's Chang'e 4 spacecraft landed on the moon on Jan. 3. Shortly after it sent back the very first photos of moon's far side. The Yutu-2 rover is now in it's ninth lunar day, which began on Aug. 25.