A small tributary of the Grand Canyon of Mars, Hebes Chasma is pictured in this high-resolution image taken by the European Space Agency's Mars Express orbiter on October 10.
Nearly 8 kilometers deep, Hebes Chasma forms a giant trough of Valles Marineris, the largest canyon system in the solar system.
Some 125 kilometers across at its widest point, the feature stretches to a length of roughly 315 kilometers. Mars scientists believe that flowing water may have carved out the entire canyon system more than a billion years ago.
Photograph courtesy G. Neukum, ESA/DLR/FU Berlin
Beneath a canopy of stars, Indonesian villagers huddle around the flames of a campfire on a cold night in Java, in this striking October 8 photograph submitted to National Geographic Your Shot.
While the Milky Way glows bright in the pristine skies, two volcanic mountains, Mount Bromo (smoking on the left) and Mount Batok loom in the distance.
Photograph by Vinay Balla, National Geographic Your Shot
Like giant ghostly wings, green auroras fly across the sky in this mountain scene taken near Anchorage, Alaska, on October 10.
These brilliant auroras were triggered by a coronal mass ejection that hit our planet early Thursday morning. A coronal mass ejection is a cloud of superheated gas and charged particles hurled off the sun.
When such an ejection hits the Earth, the solar particles can interact with charged particles caught in our planet's magnetic field to produce the northern and southern lights.