The schoolgoers were using the THEMIS to find lava tubes on the Red Plant when they came across a small black feature straddling one of the tubes.
The feature, identified as a cave or "skylight", near the Pavonis Mons volcano was a hole, punched in the top of a hollow tube.
The students, from Evergreen Middle School in Cottonwood, California, were participating in the Mars Student Imaging Program (MSIP), a part of Arizona State University's Mars Education Program.
"This pit is certainly new to us," Discovery News quoted Glen Cushing, a US Geological Survey scientist, as saying.
He added: "And it is only the second one known to be associated with Pavonis Mons."
Cushing believes the new skylight is around 190×160 meters wide and at least 115 meters deep.