Using high-resolution electron microscopes, a team from Jilin University in northeastern China detected the straw-shaped, ultra-thin tubes in samples collected by the mission.

The researchers said the structures had probably formed under extreme conditions created jointly by micrometeorite impacts, solar wind exposure and ancient volcanic activity.

Although multilayered nanotubes that formed naturally have been found on Earth as a result of natural phenomena such as forest fires or ice cores, there had been a long debate about whether single-layer carbon nanotubes could form naturally.

Producing them in laboratories needed precisely controlled temperatures and catalysts, but the Chinese team’s findings, published online in the journal Nano Letters last month, have settled the debate.