The "Happy Face Crater" on Mars Has Been Changing Right Before Our Eyes

By Nancy Atkinson January 22, 2021
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Who has an even bigger grin than ten years ago? This goofy-looking crater on Mars.

These two images were taken by the HiRISE camera (High Resolution Imaging Science Experiment) on board the Mars Reconnaissance Orbiter and shows how Mars’ surface is changing over time – in this case, due to thermal erosion.

The smiley face crater on Mars in December 2020, as seen by the HiRISE camera on the Mars Reconnaissance Orbiter. Credit: NASA/JPL/U of Arizona

The first of these images was taken in 2011 and the other in December of 2020, at roughly the same season, and show a few different changes. There are color variations that are due to different amounts of bright frost over darker red ground, according to the HiRISE team.

You’ll also see some of the “blobby” features have changed shape due to the heat of the Sun causing sublimation -- when a solid turns directly into a gas, bypassing the liquid phase.  This thermal erosion has made the “mouth” of the face larger, and the “nose” -- which consisted of two circular depressions in 2011, have now grown larger and merged.

MRO is one of NASA’s oldest and longest-lasting spacecraft. The mission launched in 2005, arrived at Mars in 2006 and has been monitoring Mars ever since. HiRISE is the most powerful camera ever sent to another planet, and it has provided a plethora of incredibly detailed images of Mars's features. Some of our favorites over the years have been avalanches in progress, dark flows that may or may not be briny material seeping to the surface, images of our own spacecraft and rovers on Mars’ surface, and many more.

An avalanche on Mars captured by the HiRISE camera on the Mars Reconnaissance Orbiter on November 27, 2011. Credit: NASA/JPL/University of Arizona.

But one major benefits of long-lasting spacecraft is being able to monitor changes in what is being observed. The HiRISE team has been documenting this “smiley face” feature for over a decade, which means we now have good side-by-side comparisons of surface changes, right before our eyes.

“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,” wrote HiRISE Co–Investigator Ross Beyer.

Check out more amazing Mars imagery on the HiRISE website.

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com