NASA’s Mars Reconnaissance Orbiter (MRO) first recorded a “smiley photo” in 2011, using the powerful High-Resolution Science Imaging Experiment (HiRISE) camera.
The researchers compared the image of the crater from October 2011 to an image from December 13, 2020, and reported that it is larger.
The growing “smile” is actually caused by thermal erosion, as carbon dioxide evaporates and more soil is exposed. The “nose” on the face has also grown from two small points to a large depression.
MRO began analyzing Mars shortly after arriving in 2006.
“You can see how nine years of this thermal erosion made the face ‘mouth’ bigger,” said Ross Bayer, a planetary scientist at the Sagan Center at the SETI Institute. By 2020, the two lows “grew and merged,” Bayer noted.
“Measuring these changes over the course of the Martian year helps scientists understand and eliminate the annual precipitation of Arctic frost,” Bayer said. Monitoring these sites over long periods helps us understand long-term climate trends on the Red Planet.
The “smile” on the figure appears larger due to the amount of frost lost due to thermal erosion, revealing more of the surface.
And although it is evaporating elsewhere on the planet, carbon dioxide ice is forming near the poles – and shifting throughout the year with climate change – which makes some “features” appear.
The facial features we see actually represent different heights and different densities of ice at the surface.
Bayer explained that the “blobby” features of the polar cap are due to the sun’s removal of carbon dioxide into these circular patterns.
This means that carbon dioxide moves directly from a solid state to a gaseous state without turning into a liquid, causing further soil erosion.
Seeing human faces and other familiar images in landscapes, and on inanimate objects is called pareidolia, and is rare when it comes to Mars.
And in late December, the European Space Agency’s Mars Express satellite captured an image of what looks like an angel, complete with a halo and wings, near the south pole of the red planet.
The angelic figure was visible due to the pattern and composition of the nearby dune fields, rich in dark, rocky minerals such as pyroxene and olivine.