NASA's Perseverance rover will save this original sample and other samples in order to return to Earth, which will "change everything in Mars science."

With the hum of the drilling rig, robotic geologists about 244 million miles away made history, collecting the first Mars sample to return to Earth. The sample is sealed in a sealed ultra-clean tube, which is an important milestone in the final answer to this question at a cost of billions of dollars: Has there ever been life on this red planet?

The successful maneuver of NASA's Perseverance rover came after the failure of the first sampling attempt last month, when a piece of fragile weathered rock at the bottom of the crater shattered. This time, the team tried in different locations and grabbed a finger-sized, more durable rock cylinder from a boulder along the nearly half-mile-long ridge.

"For all of NASA's science, this is indeed a historic moment," NASA Deputy Director of Science Thomas Zurbuchen said in a press release.

However, this process is not without problems. Although early images showed tan, speckled rocks nestled in its tube, the sample disappeared from sight after the rover shook the tube to remove dust. An extra day’s analysis revealed that the prize simply slipped into the depth of the tube, and Perseverance then safely closed the lid and stored it in its abdomen.

This sample is only the first of dozens of samples collected in the coming months. The rover will eventually store its cache on the surface of Mars, and future missions will pick it up and transport the rocks to enthusiastic geoscientists.

"It feels a bit surreal," said Vivian Sun of NASA's Jet Propulsion Laboratory (JPL), who was the co-leader of the mission's first scientific event. "What we are doing now will affect Mars science for a long time."

In addition to sampling, Perseverance is also equipped with the ability to sniff, taste, and observe the Martian landscape in more detail than ever before, helping scientists unravel the planet’s water past and find clues to Martian microbes, which may have been there. The now-disappeared rivers and lakes thrive. The stage for this dramatic search is Jezero Crater, a 28-mile wide basin carved from meteorite impacts billions of years ago.

In February 2021, Perseverance experienced a painful 7-minute fall in the thin atmosphere of Mars and landed near the edge of the crater in February 2021. Although the ground under the six wheels of the rover is now dry, the rosy rocks and sand can still provide clues that water has been washed over in the past. The scientific team will use the rover's advanced instrument suite to explore the area, selecting samples from the bottom of the volcano to the ancient river delta and beyond.

"We will be surprised," said Nina Lanza, a planetary scientist and head of the space and planetary exploration team at Los Alamos National Laboratory. "We will learn things we can't imagine."

Scientists believe that Mars was once covered by a thick atmosphere, which helped to absorb enough heat to prevent water from freezing, and to generate enough pressure to prevent the liquid from evaporating and escaping as a gas. But at some point, the atmosphere thinned and the Martian climate changed dramatically. By 3 billion years ago, the earth had dried up, and Mars became the red dust ball we see today.

Exactly why and how this happened is still unknown. Jezero's rocks provide an opportunity to study this dramatic transformation, capturing the critical period of great dryness. Kathryn Stack Morgan, deputy project scientist at NASA's Jet Propulsion Laboratory, said: "As we explore different parts of the crater inside Jezero, we may travel through time and space."

Jezero is a crater in a volcano. This planetary pit is located on the western edge of the Isidis Basin-a huge crater about 750 miles wide that was blown up by a huge space rock about 3.9 billion years ago. Later influences carved the inner rock bowl now known as Jezero. Then the water came.

The winding river overflowed from the rim of the volcano, forming an ancient lake. The water flowing into the basin slows down, causing the suspended sand and mud to sink to the bottom of the lake, forming a pair of deltas that fan out around the bifurcated waterways.

The rover will explore the dry remains of the larger delta of the crater, which lies on the western edge of Jezero. Before the river dried up about 3.5 billion years ago, the rapid accumulation of sediments in this delta could easily bury and preserve the characteristics of life if it did exist.

There is a gap on the opposite edge of this sand fan, called Pliva Vallis, which marks that water once flowed out of the lake. The presence of inlets and outlets indicates that the lake is constantly renewed, preventing the accumulation of salt to a level that may be harmful to many life forms, and may make Jezero the main place for microorganisms to multiply. 

"As a geologist, I can't help but get excited about learning about the history of Mars," said Bethany Ehlmann, a planetary scientist at the California Institute of Technology.

To collect Jezero's geological resources, Perseverance's sampling system consists of three robots that work together to drill out rock cylinders, seal them in sealed tubes, and then store them in storage racks on the belly of the rover. "This is the spacecraft in the spacecraft," said Ian Clark, a systems engineer at the Jet Propulsion Laboratory, who is part of the Perseverance team.

In Perseverance's first sampling attempt, the rover aimed at the interlocking mosaic of light reddish-brown stones that formed a large area at the bottom of the crater-this may be the oldest rock that the rover will find in Jezero. The hints from the orbit and the analysis of the rover on the ground indicate the volcanic origin of these "paving stones", as the team puts it. If this is the case, sending these rocks back to Earth will enable scientists to accurately date them using radioactive elements, helping to piece together the complex past of the region.

But the first sampling attempt left the team empty-handed. Although the rover’s sampling system initially appeared to be working as planned, the sealed tube was still empty. Later analysis showed that the interaction between the rock and the ancient water took away most of the geological glue that held it together, which caused the sample to break into pieces under the impact of the core drill.

Perseverance project scientist Ken Farley wrote in a blog post that the team did not give up hope of sampling the bottom of the crater, and they plan to eventually find paving stones with a lower degree of weathering for drilling.

But for their second and most recent drilling attempt, the team instructed the rover to look westward for rocks that were "as different as possible" from the paving stones. The rover aimed at a boulder on the ridge of the Atubi Mountains nearly half a mile long. The boulder stands high above the landscape and seems to have withstood numerous impacts, which shows that it is strong enough to withstand drilling.

Roger Wiens, planetary scientist at Los Alamos National Laboratory and principal investigator of Perseverance's SuperCam, said the boulders sampled looked similar to other rocks emerging from the bottom of the crater and are sometimes called "tall rocks." Earlier, the team planned to sample one of these towering rocks and paving stones. "But we want to start with what we think is the easiest, which is softer - and, uh, oops," Vince said with a smile.

Now, the newly deposited core confirms that the first sample was “just underperforming rock”, as Farley suspected, rather than the rover drilling and core storage mechanism.

After the first sample is safely stored, the rover will quickly turn back east and then move north to the delta to study the rock formations along the way. One feature that scientists are eager to study carefully is finely layered rocks. Such stacks can be found in sediments deposited by water, wind, or sometimes volcanoes on the earth.

In the water, the mud is slowly deposited layer by layer and accumulated in layers, which may retain the traces of Jezero’s life and the chemical composition of the now-disappeared lake—providing the “real archive” of the Natural History Museum in London Keyron Hickman-Lewis, a geobiologist and return sample scientist on the Perseverance mission in China, said the rock formed. 

Strata are common in deltas, including those of Jezero, but the rover also found promising stacks in the rock unit at the bottom of the crater. At a press conference on July 21, Farley took out a photo of the sediment at the bottom of the crater, which looked like a stack of uneven brown paper. "This is the kind of rock we are most interested in investigating," he said. But scientists are still studying the process by which these rocks are formed, whether they are sediments, volcanic rocks, or a mixture of the two, Wiens said.

On the Delta, two other attractive targets are clays and carbonate minerals. Ehlmann of the California Institute of Technology and her colleagues first discovered these targets in Jezero using orbital data more than a decade ago. On the earth, carbonates are usually closely related to life and can preserve delicate structures, such as the finely wrinkled layers of ancient microbial mats called stromatolites. Clay can quickly bury organic matter, and if there is any organic matter on Mars, they may protect it from the destructive cosmic radiation that hits the surface of the planet.

Another interesting possible research target is manganese-rich rocks. Manganese minerals can be formed in many ways, but microorganisms sometimes participate in it.

Lanza of Los Alamos and her colleagues proposed in a recent study that cyanobacteria can produce manganese-rich varnishes that usually cover rocks found in deserts around the world. Microbes can use minerals as a sunscreen to protect themselves from strong ultraviolet radiation.

Manganese was previously found in Gale Crater near Mars, and the Curiosity rover is busy with its own investigation. The team thinks they may have found some in Jezero, but they are still working to confirm its existence and determine how many there are. Manganese on Mars takes many forms and may form similar finishes on the rocks in the crater.

"If we see anything like rock varnish, we should really stop and take a closer look," Lanza said.

Once dozens of samples have been collected and cached, another mission will have to land on Earth to collect them. NASA and the European Space Agency are designing a lander equipped with an "acquisition rover" that can be launched as early as 2026.

The small rocket on the lander will bring the precious rocks into orbit around Mars, where the orbiter will grab them and bring them back to Earth, releasing the samples into a small probe, which will crash in Utah State desert.

After the samples are safely returned to Earth, scientists will use sophisticated tools to unlock any secrets in the rocky remains. But even so, the search for ancient alien life still faces severe challenges. Experts debate what kind of evidence is sufficient to identify very early life forms, even on earth. Life that existed on our planet billions of years ago claimed to have fueled years of discord and reduced disagreements among scientists.

A recent debate involved a series of 3.7 billion-year-old rocks on the southwest coast of Greenland. In 2016, a group of scientists announced that a set of wrinkled triangles in the rock were traces of microbial activity, which would make them the earliest known fossil life. But Abigail Allwood, a geologist at the Jet Propulsion Laboratory, and her colleagues are skeptical. When they returned to research outcrops, a different picture appeared. These wrinkles are not caused by microbial agitation, but by the geological process of squeezing the stone.

"There is nothing like standing in front of the head to let you know what's going on. You can't do this through a camera lens," Allwood said. When she realized what she was saying, her words were caught, and she added with a smile, "This is exactly what we are trying to do on Mars."

Since the human team cannot stand on Mars in person, Perseverance allows them to observe rocks on multiple scales-from panoramic images to chemical analysis of the size of rock spikes. Allwood is the lead researcher of Perseverance's PIXL instrument, which can take images of tiny features and use X-rays to measure the chemical composition of Martian rocks.

Nevertheless, so much can only be inferred from a distance, which is why sampling is so important. When these samples come back, they will observe the original matter of the red planet up close for the first time. As Lanza said: "This will change everything about Mars science."

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