At this point in its mission, NASA’s Mars Perseverance Rover has collected almost 50% of its samples. The rover is now building its first sample “depot” on the Martian surface. The depot is a flat, obstacle-free area with 11 separate landing circles, one for each sample tube and one for the descent module.
A future mission will retrieve these samples by helicopter.
Studying samples from Mars will be a highlight for eager planetary scientists. Even with everything we’ve learned from orbiters, landers, and rovers, having Martian samples in fully functional Earth labs will allow for comprehensive exploration that simply isn’t possible with robotics, even with Perseverance’s suite of advanced instruments.
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There is still a long time until the Perseverance rover’s samples are returned to Earth in 2033, but the rover is collecting samples and beginning to store them in a repository. Perseverance collected 18 of 38 samples or 47%. The majority of these are samples of rock grains, but there are also samples of regolith and atmosphere.
The vast majority of Perseverance’s 18 samples so far are rock samples. Image credit: NASA/JPL.
Placing the samples on the surface is a detailed process. Pipes are not simply left on the ground. Since they will be retrieved by helicopters at a later date, they should be positioned so that the helicopters can access them one at a time. This means that the entire landfill area must contain 11 separate landing sites.
Complex operations like this must be planned precisely, and without adequate room for maneuver, the entire undertaking can become far more complicated than necessary, and may even risk failure.
It is even more critical when the site is on another planet.
“So far, Mars missions have only required one good landing zone; we need 11,” said Richard Cook, manager of the Mars Sample Return Program at NASA’s Jet Propulsion Laboratory in Southern California. “The first one is for the sampler lander, but then we need another 10 nearby for our sampler helicopters to do take-off and landing as well as driving.”
“You can’t just drop them in a big pile because rescue helicopters are designed to only interact with one pipe at a time,” Cook said.
This map shows where NASA’s Perseverance rover will drop 10 samples that a future mission might pick up. Orange circles represent areas where a sample retrieval helicopter can safely operate to retrieve the sample tubes. Credit: NASA/JPL-Caltech
Perseverance collects duplicate samples from each of its sampling locations. One of each sample will be placed in a surface repository as a backup, and one will be stored in Perseverance. NASA and ESA refined the architecture of the Mars Sample Return mission over time. Previously, the plan included a rover to collect the samples and a lander to return the samples. But with the success of Ingenuity Helicopter, that plan changed.
This artist’s illustration shows what an example return helicopter might look like. The helicopters would collect the cached sample tubes with their robotic arms, one at a time, and return them to the sample return module. Image credit: NASA/JPL-Caltech.
The sample return mission will still include a sample return lander, but instead of a rover, two helicopters will collect the samples. But the helicopters and landfill samples are just a backup plan. NASA and ESA now plan to have Perseverance deliver the samples to the Sample Return Lander, where a small rocket will launch the samples into orbit. There they will be picked up by another spacecraft, the Earth Return Orbiter, which will send them back to Earth.
This is what the Mars Sample Return mission looked like in 2019. The updated plans eliminate the Fetch Rover (yellow ellipse) and will instead use sample retrieval helicopters to bring the samples to the Sample Return Module. Once they reach the lander, the samples will be launched into orbit by a rocket, then retrieved by an orbiter and sent back to Earth. Credit: ESA
The return of the samples is still a long way off, but the choice of a depot and the positioning of the samples is another milestone in the journey to that rewarding day in 2033. The site of the depot has been named Three Forks, and once the full set of samples has been collected, the samples in Three Forks will cover rehearsals at Perseverance.
“The samples for this depot — and the duplicates stored aboard Perseverance — are an incredible set representative of the area explored during the main mission,” said Meenakshi Wadhwa, principal scientist of the Mars Sample Return Program at Arizona State University . “Not only do we have igneous and sedimentary rocks that record at least two and possibly four or even more different styles of water alteration, but also regolith, atmosphere, and a witness pipe.”
Sample depot: 40% complete!
Another successful tuba drop adds to my growing collection here at the Three Forks location. Four of the 10 tubes I leave here as a spare set are not working. More about my samples: pic.twitter.com/UNjgtqSFh2
— NASA’s Mars Rover Perseverance (@NASAPersevere) January 4, 2023
The complexity of the Sample Return mission is fascinating on its own. It includes multiple launches from Earth, a surface rover and a surface lander, helicopters, an ascent and a return to Earth orbit. In a way, it’s a celebration of human ingenuity.
But in the end it all comes down to the samples and what they will tell us about Mars.
Mars is a puzzle that cannot be completed. It is remarkable that we have learned so much about the planet. But the missing piece is a set of samples from the planet that scientists can study on Earth.
Before Perseverance was released, a lot of work went into planning its rehearsals. These first samples are from the bottom of the Jezero crater. They form a set of samples of what is called the Séítah Formation and the Máaz Formation.
This image shows Perseverance’s route early in its mission, from Sol 0 to Sol 204. The Séítah Formation and the Máaz Formation are indicated. Image credit: Hamran et al. 2022
Scientists believe that the Séítah geological unit is similar to places on Earth where volcanic flows meet the ocean, such as Hawaii or Iceland. The igneous rocks of Séítah probably formed when a dense underground lava or magma chamber cooled. Jezero Crater is an ancient paleolake, so eventually this lava came into contact with water that filtered through the cracks created by whatever impact on Mars and created the crater. This may have led to life-supporting conditions.
Séítah contains a common mineral called olivine, a mineral that reacts more quickly with water than other minerals commonly found with it. And Perseverance has already shown us that olivine was slightly altered by water in at least two exposure phases. This means that water is probably slowly percolating through the bottom of Jezero Crater. During any exposure of olivine to water, water that migrates through cracks and fissures in the rock can support life. The activity would also form new minerals, and these minerals could contain evidence of ancient life, if it existed.
These annotated images from December 2021 show two views of the “Séítah” geological unit of Jezero Crater on Mars. The map on the left shows the crater’s terrain features with annotations depicting the rover’s route during its first science campaign. “Artuby” is a ridge running along part of the southern border of Séítah. “Dourbes” is the name of an abrasion target on a rock at South Séítah. The multicolored map on the right shows the variety of igneous (solidified by lava or magma) minerals in the same region. Olivine is shown in red. Calcium-poor pyroxene in green. Calcium-rich pyroxene is in blue. Image credit: NASA/JPL-Caltech/CRISM/CTX/HRSC/MSSS/USGS
But Perseverance also discovered some useless chemicals called perchlorates. They are rare on Earth and toxic to life. They contradict life in the Jezero crater, but not completely. Much remains to be unraveled.
This is why samples are so important. Perseverance is a remarkable machine, but it has its limitations. Only by returning these samples back to Earth and performing more rigorous studies than Perseverance is capable of can we hope to find deeper answers about Mars’ past. Maybe then we can confirm whether microbes lived there or not.
Perseverance’s main quest ends today, January 6th. So far, Perseverance has collected about half of its samples. After it finishes depositing samples at Three Forks Depot, it will head to the top of the nearby delta in its next science phase, which the Perseverance team is calling the Delta Top campaign.
This image is from NASA’s interactive map. It shows sampling sites in red, the rover in blue, and Ingenuity’s flight regions in blue. Perseverance will leave the bottom of Jezero Crater and climb to the top of the delta above it in this image. Will take his next samples from the delta. Image credit: NASA.
Sometime in February, Perseverance will climb the steep embankment to the top of the nearby delta. Delta Top samples will differ from crater floor samples.
Perseverance’s range is limited, but it can extend it by traveling to the top of the delta. There, ancient flowing water deposited rocks and rocks from elsewhere on Mars. By sampling this region, scientists can gather a more diverse collection of samples than is possible on the Jezero crater floor.
“The Delta Top campaign is our opportunity to peer into the geologic process beyond the walls of Jezero Crater,” said Katie Stack Morgan of JPL, deputy project scientist for Perseverance. “Billions of years ago, a raging river…
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