When NASA designed the Perseverance mission, which aimed to collect samples of Martian soil, it was immediately clear that bringing them back to Earth for in-depth analysis would be a feat more than epic – for many, almost impossible. So far, the only analyzed samples of Martian soil have been transported by asteroids that have fallen on our planet.
These fragments, generated by powerful impacts on Mars, have reached Earth and allowed us to make preliminary but very rough analyses of the composition of Martian soil. This is how the so-called acondritic meteorites were born, which originated from the red planet. But how will it be possible to bring the rocks collected by the rover on the surface of Mars back to our planet?
The Mars Sample Return Program
The answer lies in the acronym MSRP (Mars Sample Return Program). NASA has finally completed the review of the program’s system requirements, which is about to complete the conceptual design phase. The team has evaluated and refined the architecture for returning scientifically selected samples. They are currently being collected by the Perseverance rover in the Jezero crater on the red planet.
Campaign architecture, which also includes the contribution of the European Space Agency (ESA) and Italy’s Leonardo, should reduce the complexity of the mission and increase the chances of success. “The conceptual design phase is when every aspect of a mission plan is examined under a microscope” said Thomas Zurbuchen, scientific administrator at NASA. “There are some significant and advantageous changes to the initial plan that can be directly attributed to the recent successes of Perseverance at Jezero and the incredible performance of our Mars helicopter”.
Mission architecture takes into account a recently updated analysis of the expected longevity of the Perseverance rover. The complex mission will involve three vehicles: the Sample Retrieval Lander (SRR), which carries the Mars Ascent Vehicle (MAV) and the Earth Return Orbiter, provided by the ESA.
Phase 1: Landing and Sample Collection
The first phase will be very complex. Everything needed to collect the samples must be brought to Mars, leave the Martian atmosphere, and return to Earth. The payload will be cumbersome, and it won’t be easy to delicately land about 2400 kg of lander on the Martian surface, about twice the weight of the Perseverance rover. To be clear, we’re talking about the heaviest payload ever landed on the surface of another planet. The retro-rockets that are usually used to land rovers alone will not be enough. They will inevitably have to be aided by cushioned legs, which are currently being tested at JPL (Jet Propulsion Laboratory).
Once the Sample Retrieval Lander has landed, two helicopters based on the Ingenuity helicopter design, will be launched for sample recovery. The Perseverance rover will place the delicate rock core samples in a predetermined collection point to facilitate the work of the helicopters. It will transport the load back to the lander. This is where the Sample Transfer Arm (STA) comes into play, designed and built by Leonardo. This robotic arm will be able to see, feel and make autonomous decisions, and finally, identify, collect, and transfer the tubes into the Mars Ascent Vehicle.
Phase 2: Rocket Launch
If phase one was complex, the second is truly something out of science fiction: bringing the sample payload into orbit. The Sample Retrieval Lander weighs over two tons because it also contains the Mars Ascent Vehicle, a two-stage rocket about 2.8 meters tall, in addition to the helicopters. While the planet’s lower gravity should reduce the fuel needed to put the rocket into orbit. The lack of an atmosphere makes controlling the vehicle in flight more complex as it can easily tilt.
Furthermore, since there is no traditional launch platform, even the simple ignition of the rocket will become terribly complicated on Mars. To solve this complex challenge, JPL engineers have developed a system that will be used for the first time on this mission and will become the first rocket to launch from another planet. The Mars Ascent Vehicle will be thrown into the air before the engines ignite. The system, still in the testing phase on Earth, is called VECTOR (Vertically Ejected Controlled Tip-off Release). In this way, it will be possible to launch the vehicle at a height of about 3.3 meters.
Phase 3: Return to Earth
After completing the first two phases, the mission will become much simpler. The payload will be attached to the orbiter built by ESA: the Earth Return Orbiter. The vehicle will seal the samples in a bio-containment system to prevent contamination on Earth with non-sterilized material, before they are moved into a terrestrial entry capsule. At that point, the payload will safely land on our planet. With launch dates planned for the Earth Return Orbiter and Sample Retrieval Lander in the fall of 2027 and the summer of 2028 respectively, the samples should arrive safely on Earth in 2033.
The State of the Mars Sample Return Program
With the architecture now decided during the conceptual design phase, the program is expected to enter the preliminary design phase in October 2022. During this period, expected to last about 12 months, the program will complete technological development and create the first engineering prototypes of the three components of the mission. The refined Mars Sample Return project was presented to delegates from the 22 participating states in the space exploration program in May 2022.
“ESA is proceeding full steam ahead with the development of both the Earth Return Orbiter. It will make the historic round trip, and the Sample Transfer Arm, which will robotically position the tubes inside the Orbiting Sample Container before its launch from the surface of the Red Planet” said David Parker, Director of Human and Robotic Exploration at ESA. The first step of the sample return campaign is thus already underway. Since landing at Jezero Crater on February 18, 2021, the Perseverance rover has collected 11 scientifically compelling rock core samples and one atmospheric sample.
This mission will allow scientists to examine the Martian samples using sophisticated instruments that are too large and complex to be sent to Mars. It will also enable future generations to study them. Caring for the samples on Earth will allow the scientific community to test new theories and models.