It’s another first for NASA.
In early September, the Perseverance rover successfully used its robotic arm and drill to drill into a rock and extract a sample. It extracted a rock core about 6 cm (2 in) long and placed it inside a sealed tube. This is the first time a robotic spacecraft has collected a sample from another planet destined for a return to Earth on a separate spacecraft.
Now we wait for the eventual return of the sample to Earth.
Missions to Mars keep getting more and more complex. It’s been about 45 years since Viking 1, the first lander on Mars, made it to the surface of the planet. It sat there at Chryse Planitia for over six years, taking soil samples and searching for signs of life. Almost all scientists agree that it didn’t find any signs of life (some still think that Viking 1’s labelled release experiment showed signs of life.) But it did characterize the Martian soil and atmosphere. It also found striking evidence of liquid water flowing over the planet’s surface in the ancient past.
Look at how far Mars exploration has come since then.
The Perseverance mission is a triumph of complex engineering, technology, and mission design. It was built on the shoulders of previous successful NASA rover missions to Mars, especially MSL Curiosity. But it’s more ambitious than even its most recent predecessors because it’s collecting samples and caching them on the surface for eventual return to Earth.
Altogether, Perseverance is carrying 43 sample tubes. 38 of them are designated for samples, and the other five are witness tubes. The witness tubes were filled with materials prior to launch and are used to capture molecular and particulate contaminants at sampling sites. They’re designed to “… catalogue any impurities that may have travelled with the tube from Earth or contaminants from the spacecraft that may be present during sample collection,” according to NASA. Each of the rest of the 38 sample tubes can carry a sample of a solid or a sample of a gas.
Martian rock is ancient rock. The planet isn’t geologically active, so it doesn’t make any new rock. Its volcanoes are all inactive, and there is no plate tectonics. Jezero Crater, where Perseverance is working, is in the Isidis Planitia impact basin. The rocks there date back to Mars’ Noachian period, which spans from about 4.1 billion to 3.7 billion years ago. Rocks from that time period are prime targets in the search for life because Mars was much different then.
The atmosphere was thicker, and the climate was warmer. There may even have been rainfall. The rover’s first sample is from the “South Séítah” region of Mars’ Jezero Crater, and according to NASA it may contain some of the deepest, and potentially oldest, rocks in the giant crater. If there is fossilized evidence of ancient microbial life on Mars, it could very well be in the rocks that Perseverance is sampling at South Séítah.
Getting samples from Mars back to Earth is a huge deal to geologists. Earthly laboratories are far better equipped than the Perseverance rover when it comes to studying samples. And we’ll keep developing better, cutting-edge technologies while the Perseverance rover continues on its mission. By the time the samples ever get to Earth, technology will have advanced even further. Who knows what exactly we’ll learn from the Martian samples?
It’ll be several years before the samples ever land on Earth. The sample-return mission is still being designed, and Perseverance will be collecting samples for years.
But getting the precious samples back to Earth is not a done deal. The separate mission to retrieve the samples and bring them to Earth is extremely complex. It involves multiple spacecraft and multiple space agencies. And at this point, it’s only a proposed mission.
The ESA and NASA are working together on the sample return mission. Many details are yet to be worked out, but the agencies have agreed on the overall architecture. In July 2026 a spacecraft would be launched to Mars that consisted of a lander, a rover, and an ascent rocket. Once on the surface in 2028, the lander would deploy the sample gathering rover to collect the samples. If Perseverance is still operating at that time, it could retrieve samples too.
Once the samples are all gathered, they’ll be placed inside a sample return capsule in the ascent rocket. An additional spacecraft, designed and built by the ESA and called the Earth-return orbiter, will be launched from Earth in 2026. It’ll enter a low Martian orbit by July 2028. Then, the ascent rocket carrying the sample return capsule will be launched into orbit, too.
The rocket and the Earth-return orbiter will rendezvous in low Mars orbit, and a robotic arm on the return orbiter will take the sample return capsule from the rocket. The samples will be placed in an Earth return capsule and returned to Earth during the 2031 Mars-Earth transfer window.
A lot has to go right for all of this to work. Getting all the spacecraft launched and landed safely is a challenge in itself. So is the rendezvous between the ascent rocket and the orbiter. But there are a whole host of other obstacles that may not be obvious.
One of the obstacles involves extreme temperatures. The return capsule has to be sealed and sterilized to protect the samples from contamination. The team designing the system is looking at brazing the capsule shut. Brazing uses heat to join pieces of metal together, and the heat also sterilizes everything. But, the samples themselves have to be protected from extreme heat. The idea is to never subject the samples to temperatures higher than they were subjected to on Mars, for obvious reasons.
“Among our biggest technical challenges right now is that inches away from metal that’s melting at about 1,000 degrees Fahrenheit (or 538 degrees Celsius) we have to keep these extraordinary Mars samples below the hottest temperature they might have experienced on Mars, which is about 86 degrees Fahrenheit (30 degrees Celsius),” said Brendan Feehan, the Goddard systems engineer for the system that will capture, contain, and deliver the samples to Earth aboard ESA’s orbiter. “Initial results from the testing of our brazing solution have affirmed that we’re on the right path.”
Scientists like Meenakshi Wadhwa, who is the principal scientist for the Mars Sample Return program, are very excited to get these ancient samples into labs here on Earth. In a press release, Wadhwa said, “I have dreamed of having Mars samples to analyze since I was a graduate student. The collection of these well-documented samples will eventually allow us to analyze them in the best laboratories here on Earth once they are returned.”
Once on Earth, the samples will likely be analyzed and re-analyzed for decades to come. That’s what’s happened with lunar rocks brought back from the Moon in the Apollo missions. As we keep developing new technological tools to study them with, scientists keep learning more and more from them.
The same will be true of these Martian samples. If the sample return mission succeeds.