For the Perseverance Rover team at NASA’s Jet Propulsion Laboratory (JPL), the hours before dawn on August 6 are like Christmas Eve. A few hours ago, scientists ordered the rover to drill into a rock in Mars’ Jezero Crater to extract and store the mission’s first Martian geological sample — one of as many as 43 samples, which will one day be Ship to the earth and check its signs of ancient life.
At around 2 in the morning, when they started looking at the new data sent by the rover from Mars, everything seemed to be going well: the sample appeared to have been collected and placed in one of the rover’s 43 storage tubes. But soon there was an annoying surprise, a probe designed to measure the volume of the first precious sample: the tube seemed to be empty. The subsequent pictures of the pipe confirmed the worst case: It was Christmas and Santa Claus forgot to bring some geological gifts to show up. “This is definitely an’oh damn’ moment,” said Ken Farley, Perseverance project scientist at the Jet Propulsion Laboratory.When the team ordered the rover to take a snapshot of its surroundings, the chaos reached its peak-including Inside the hole By itself-and still unable to find the missing rock sample. Where did it go? If Perseverance’s sample collection hardware has fatal flaws, what will happen to the multi-billion-dollar meticulous plan to retrieve rocks from Mars?
After a week of intense and urgent investigations, the team concluded that the problem is not the rover, its performance is flawless. On the contrary, the rock itself deceived the scientist. “Basically, the rock was crushed,” Farley said. Although it looks like a solid and solid stone, which is perfect for drilling, inside the rock, it is a grainy, fragile mess. When it is drilled, the sample will spread out. The “missing” core can be found at least partially in the form of fines in the tailings piles surrounding the borehole, although the final location of most samples is still unclear.
The good news is that most of Jezero’s rocks may not be equally deceptive, and no hardware accident is doomed to the grand mission of bringing Martian debris to Earth. “We have reason to believe that this is a one-off, strange rock, and we are attracted in some ways precisely because it is strange,” Farley said. People now hope that the next sample attempt, which may be carried out within a month, will prove successful.
At first glance, the target rock of the Perseverance’s or “Percy’s” groundbreaking ceremony looks too good to be true. Its surface is very flat: a simple appearance on which the drill can be started. The abrasive tool wipes away dust from a small surface and encounters sufficient resistance because it indicates that the rock is relatively hard. When the team members compared instrumental data studying the geochemical composition of the stone with photos of the shimmering crystals of worn-out plaques, they initially determined that it was a cold-resistant igneous rock called gabbro, when the magma slowly cooled deep underground form.
The team fully expects that the prize will provide a cohesive sample when drilling. Igneous rocks also contain radioactive compounds that can be used for precise geological dating—so this rock is one of Jezero’s oldest rocks and can be used to limit the time that the area was formed billions of years ago.
The team sent an order to drill on the evening of August 5. From then on, until the sample tube is sealed and stored, the whole process is autonomous. Scientists can only wait; those with nerves robbed of hours of sleep. “We wake up at 2 in the morning [the next morning] See if coring works, and it works,” said Jennifer Trosper, Perseverance project manager of JPL. The image shows a perfect borehole in the rock, and telemetry indicates that a sample tube has been processed and stored in a room at the bottom of the rover. After a few hours, an image of the sealed sample tube appeared. “We thought,’Wow, this is great,'” she said-at least, until the probe returns more data showing empty space than the stones inside.
The emotional whipping is serious. “We really thought we put it in the bag,” Farley said. “And we don’t.”
In retrospect, it is now clearer that gabbro will never get along with a core drill. The rock was covered with rust, surrounded by debris peeling off its surface, and seemed to have been altered and weakened by the water that once flowed through Jezero, when the crater had a lake fed by a river. It is worth noting that no one seems to have seen this turning point in the plot. Engineers performed more than 100 tests on the sampling device on Earth, in a room that simulated the temperature and pressure of the environment on the surface of Mars. The Percy core drilling rig is compared with the various rocks that geologists expect to find in Jezero, from loosely stacked sedimentary types to nail-hard volcanic basalts.
“We have never seen a failure mode where the core disappears,” Farley said. But in rare cases, “we have seen a failure mode where the core smashes and falls back into the hole.” This happens when the drill bit penetrates into a structurally fragile sedimentary rock, but not any igneous rock.
In future sampling attempts, it is not impossible that another naughty mushy rock may defeat Percy’s core drill. “There are many reasons why the core collapses into powder”, even though the rock looks hard, he said Manish Patel, A planetary scientist at the Open University of the United Kingdom. Any rock may look reasonable on the surface, but it turns out to be unstable and porous or cracked when drilling.
It is frustrating not to obtain a sample of this gabbro, but scientists have learned valuable lessons from short-lived failures. “We now have a better understanding of the physical properties of rocks on Mars, and this knowledge is essential to inform future Mars drilling work in Perseverance and other fields,” Patel said.
At least Percy’s team won the consolation prize.Throughout the mission, scientists have shown “great interest in obtaining samples of the Martian atmosphere,” said Maria-Pas Zorzano, A researcher at the Spanish Center for Astrobiology and a European return sample consultant for the Perseverance Team. Now, thanks to the faint wisp of Martian air in this tube, they have one.
Trosper said that the next sampling attempt will be more cautious. The automatic coring and storage process can be manually interrupted at some point—for example, before sealing and storage, the team can ask Percy to look at the sample tube to make sure it contains geological gold before continuing.
Farley said Percy may be led back to this place in the future to try to catch some igneous rocks.But for now, the rover is heading to a new location in Jezero: trying the boundary of the elusive geological unit of the first sample, called the crater floor fractured and rough, another layered unit in the crater is called SetaThe layers of the second unit may consist of ancient sediments or volcanic ash finishes. Either way, it is lithologically different from the gabbro that was once flooded-the team members are optimistic that this time, they will get their most important first sample.
“Continue playing, Mars. Continue playing,” Trosper said. “We will fix it. We will get our core.”