In the grand scheme of things, cosmos-wise, Mars is relatively young (a mere 4.6 billion years old to the universe’s 13.7 billion), which means it could still be in its pimply phase, as it appears in new NASA images.
However, what may look like a spot of acne or a hormonal breakout on the Red Planet’s surface is actually something even more curious: an optical illusion.
Mars is no stranger to being the subject of humans’ curious propensity for pareidolia – seeing familiar shapes like cats or muppets or tombs where they definitely are not – but in this case, it’s not even that.
In this new image released this week taken by NASA’s High Resolution Imaging Experiment (HiRISE), what looks like white patches on red hills is the opposite – it’s seasonal carbon dioxide ice lying inside huge depressions in Mars’s South Pole.
It's not the first time the surface of Mars has played visual tricks on us. This elongated pit in the Ceraunius Fossae in the northern Tharsis region of Mars is also a depression rather than a raised feature, despite looking otherwise.
According to a HiRISE blog, the cluster of craters in the new image is unusual because most of the craters seen near the South Pole have been single ones. It's thought crater clusters form when an incoming space rock breaks up in Mars's atmosphere, creating a closely scattered group of impact craters rather than just one.
A more recent study found more than half of new small impacts detected by HiRISE are clusters, and that rather than Mars's atmosphere, it was the weakened state of the impactor rocks themselves that caused them to break up.
NASA's InSight recently recorded the largest meteor impact to hit Mars yet, and thanks to HiRISE they even managed to find and photograph the impact crater, measuring a whopping 150 meters (492 feet) across.