The world's first basalt flag is placed on the far side of the moon on June 4. [Photo/Changjiang Daily]

On the morning of June 4, the national flag of China, carried by the Chang'e 6 lander, was successfully unfurled on the moon's far side. This marked China's first independent display of the national flag on the moon's far side, and the flag, made in Wuhan, is the world's first basalt flag.

The Chang'e 6 national flag was developed over the course of four years by a team led by Academician Xu Weilin at the State Key Laboratory of New Textile Materials and Advanced Processing Technologies of Wuhan Textile University. The flag is mainly made of basalt, measures 200 millimeters by 300mm, and weighs only 11.8 grams.

The fiber made of basalt. [Photo/Changjiang Daily]

Unlike the spray-painted flags used on Chang'e 3 and Chang'e 4 missions, the Chang'e 5 flag was made from a new composite material primarily consisting of aramid. The Chang'e 6 flag, however, is made from a basalt-based composite material. Both the Chang'e 5 and Chang'e 6 flags are wrinkle-free, colorfast, and resistant to extreme temperatures. However, the Chang'e 6 flag is stronger and lighter, and it does not discolor even under lunar surface radiation conditions.

Basalt is a type of volcanic rock, usually black, and is a significant component of both the lunar surface and Earth's crust. Future lunar base construction will require local materials, and using lunar basalt to make sheet or tubular building materials for construction would significantly reduce costs compared to sourcing materials from Earth.