Edited Mars Reconnaissance Orbiter image of a field of sand dunes being monitoring by the USGS. Color variant.

Edited Mars Reconnaissance Orbiter image of terrain south of Mangala Fossa. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of sand dune alcoves in Chasma Boreale on Mars. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of part of Coprates Chasma, itself part of Valles Marineris. Color variant.

Edited Mars Reconnaissance Orbiter image of sand dunes on the floor of Renaudot Crater. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of a field of sand and buttes in Ophir Chasma.

Edited Mars Reconnaissance Orbiter image of a dust devil seen from the top soon after it formed on Mars.

Edited Mars Reconnaissance Orbiter image of channels and sand dunes in Aram Chaos on Mars. Color/processing variant.

Heavily processed image of Assam. I used a Mars Reconnaissance Orbiter image of Danielson Crater as the seed image.

Edited Mars Reconnaissance Orbiter image of an eroding edge of a crater in Maadim Valls. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of gullies exposing layers of different-colored bedrock on Mars.

Edited Mars Reconnaissance Orbiter image of layers in Hellas Planitia on Mars.

Edited Mars Reconnaissance Orbiter image of an interesting part of Mars from a mineralogical view point.

Edited Mars Reconnaissance Orbiter image of a crater in polar terrain.

Edited Mars Reconnaissance Orbiter image of rocky ground and sand dunes.

Edited Mars Reconnaissance Orbiter image of terrain west of Mclaughlin Crater.

Edited Mars Reconnaissance Orbiter image of a field of sand dunes being monitoring by the USGS.

Edited Mars Reconnaissance Orbiter</b image of atypical landforms in polar erg sand dunes. Color variant.

Edited Mars Reconnaissance Orbiter image of layered bedrock in the Meridiani Region. Processing variant.

Edited Mars Reconnaissance Orbiter image of part of a crater in Tempe Terra.

Edited Mars Reconnaissance Orbiter image of a steep scarp on the edge of the north polar layer on Mars. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of rocky outcroppings in Mawrth Vallis on Mars. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of sand dunes buried by water ice. Color variant.

Edited Mars Reconnaissance Orbiter image of dunes in Jeans Crater.

Edited Mars Reconnaissance Orbiter image of a candidate landing site for NASA's Mars 2020 rover mission, in Gusev Crater (the same crater where Spirit Landed in 2004).

Edited Mars Reconnaissance Orbiter image of low albedo (low reflectance) slopes in Coprates Chasma.

Edited Mars Reconnaissance Orbiter image of a 144 meter circular feature in the south polar region of Mars.

Edited Mars Reconnaissance Orbiter image of a circular feature (not necessarily a crater) in the residual ice cap of the South Pole of Mars.

Edited Mars Reconnaissance Orbiter image of dunes named Tleilax. Color variant.

Edited Mars Reconnaissance Orbiter image of an eastern watershed for Jezero Crater on Mars.

Edited Mars Reconnaissance Orbiter image of sand dunes in Nili Patera. Color variant.

Edited Mars Reconnaissance Orbiter image of dust devil tracks in Brazos Basin.

Edited Mars Reconnaissance Orbiter image of sand dunes in Nili Patera. Color variant.

Edited Mars Reconnaissance Orbiter image of "colorful" gullies in Krupac Crater. Color variant.

Edited Mars Reconnaissance Orbiter image of sand dunes (continuing the Martian circuit board theme) rich in gypsum in a Martian north polar erg.

Edited Mars Reconnaissance Orbiter image of gullies on the side of Heaviside Crater.

Edited Mars Reconnaissance Orbiter image of the colors at the top of Coprates Chasma on Mars. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of part of Mawrth Vallis on Mars.

Edited Mars Reconnaissance Orbiter image of sand dunes in Nili Patera.

Edited MRO image of defrosting patterns on ridges in an area of Mars known (colloquially) as "Inca City."

Edited Mars Reconnaissance Orbiter image of a dune field in east Endeavour Crater, which is where Opportunity is currently operating. Color variant.

Edited Mars Reconnaissance Orbiter image of West Ladon Valles on Mars. Color/processing variant.

Edited Mars Reconnaissance Orbiter image of part of Aram Chaos.

Edited Mars Reconnaissance Orbiter image of an impact crater and lava channel south of Noctis Labyrinthus on Mars.

Edited Mars Reconnaissance Orbiter image of ejecta from sublimating carbon dioxide in the Martian south polar area.

Edited Mars Reconnaissance Orbiter image of a crater in the south polar region of Mars that appears to be smiling for the camera. Color/processing variant.

Image source: www.uahirise.org/hipod/ESP_067414_0945

Original caption: We’ve monitored the so-called Happy Face Crater in the south polar region of Mars for almost a decade. Two images that we took, one in 2011 and the other in 2020, at roughly the same season, show color variations that are due to different amounts of bright frost over darker red ground.

The “blobby” features in the polar cap are due to the sun sublimating away the carbon dioxide into these round patterns. You can see how nine years of this thermal erosion have made the “mouth” of the face larger. The “nose” consisted of a two circular depressions in 2011, and in 2020, those two depressions have grown larger and merged.

Measuring these changes throughout the Martian year help scientists understand the annual deposition and removal of polar frost, and monitoring these sites over long periods helps us understand longer term climate trends on the Red Planet.

ID: ESP_067414_0945

date: 13 December 2020

altitude: 247 km

NASA/JPL/UArizona

uahirise.org/hipod/ESP_067414_0945

Edited Mars Reconnaissance Orbiter image of a pit south of Arsia Mons.

Edited Mars Reconnaissance Orbiter image of sand dunes in Nili Patera on Mars.

Edited Mars Reconnaissance Orbiter image of the floor of a crater located near Voeykov Crater.