The Curiosity rover has revealed many surprises on the surface of Mars, but its most recent one is of a totally different kind.
It started like any other drilling attempt.
On 25 April 2026, the rover plunged its rotary-percussive drill into a rock named Atacama, hoping to pulverize the material into powder that can then be examined in greater detail; so far, standard.
However, when Curiosity extracted the drill, the entire 13-kilogram (28.6-pound) slab of rock just… came up with it. Oops.
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This has never happened before in Curiosity’s 13.5 years on Mars, NASA noted in a blog post.
“Drilling has fractured or separated the upper layers of rocks in the past, but a rock has never remained attached to the drill sleeve,” the agency explained.
The fact is that, even with all the stress-testing in the world, Earth’s engineers can never predict all the problems a rover is going to face on another planet, hundreds of millions of kilometers away.
Even small differences in rock structure – tiny fractures, variations in hardness, or how layers are bonded together – can change how it behaves under stress.
On Earth, these properties can be studied directly. On Mars, they often only reveal themselves the moment a drill makes contact.
A hole drilled by the Curiosity rover in a rock named Nevado Sajama in December 2025. (NASA/JPL-Caltech/MSSS)
Curiosity has had something of a troubled relationship with the terrain of Mars since it arrived on the red planet in 2012 – and its drill in particular has had several setbacks.
The tool combines the rotary motion usually associated with drilling with percussive (hammering) force, designed to chip the rock apart into a fine powder.
That powder is then collected by the rover and delivered to onboard instruments that analyze its chemistry and mineral composition.
The 42 holes Curiosity had drilled by August 2024. (NASA/JPL-Caltech/MSSS)
Problems surfaced as early as 2015, when electrical shorts emerged in the percussive mechanism. In late 2015, another issue arose: a suspected piece of debris hampering the brake.
Then, in November 2016, the drill feed stalled, related to the same brake issue, and, after degradation that continued into mid-2017, drilling was suspended indefinitely.
After extensive testing, NASA engineers devised a workaround, and drilling recommenced in 2018.
Since then, its drilling operations have yielded several major discoveries, including long-chain alkanes in the Martian mudstone, which are difficult to explain using some known non-biological processes, according to NASA.
A selfie Curiosity took next to a hole it drilled in February 2020. (NASA/JPL-Caltech/MSSS)
Luckily, the Atacama rock did not remain stuck on Curiosity’s arm for too long.
Initially, the Earth-based Curiosity team tried vibrating the drill to try to shake the rock loose. It remained stuck.
On April 29, they tried again. Sand fell off Atacama, but the rock still did not budge.
Finally, on May 1, the rock was dislodged.
“Curiosity’s team tried again, tilting the drill more, rotating and vibrating the drill, and spinning the drill bit,” NASA wrote.
“The team planned to perform these actions multiple times, but the rock came off on the first round, fracturing as it hit the ground.”
Curiosity’s mission was initially only planned for a duration of about two years.
The discoveries the rover has enabled have revolutionized our understanding of Mars, from its water history to its geology to possible signs of ancient microbial life.
Related: Life on Mars? NASA’s Stunning Discovery Is The Best Evidence Yet
Over the years, the rover has climbed Mount Sharp, analyzed ancient lakebed sediments in the Gale Crater, and detected organic molecules preserved in Martian rock.
It’s starting to show signs of wear, but Curiosity is still going strong – thanks in no small part to the engineers on Earth who keep finding ways to adapt when Mars throws something unexpected its way.