Your Guide to Mars Sample Return

An international project to bring Mars to Earth

At a Glance

  • Mars Sample Return is a series of missions by NASA and the European Space Agency to return samples from Mars’ surface to Earth by 2031.
  • Despite advances in space technology, certain science questions—including whether or not a Mars rock sample contains signs of ancient life—can only be answered in Earth-based laboratories.
  • This will be the most ambitious Mars mission in history and require sustained public support to succeed. Making the mission happen is one of The Planetary Society’s top priorities, and you can help.

Why do we need Mars Sample Return?

Humans have been exploring Mars with robotic spacecraft since the 1960s. We have learned that liquid water once existed on the surface, and that the planet had a warm, wet environment that could have supported life as we know it.

Was Mars warm and wet for long periods during which life could have arisen, or mostly cold and dry with only brief intervals that could have supported life? What was its early atmosphere like? Can we find direct evidence of past life there, such as fossilized microbes or ancient chemical signatures that resemble life as we know it?

These answers can be found in Mars’ rocks and soil, which lock in atmospheric gases, preserve signs of past life, and carry clues revealing the environment in which they formed. Despite impressive advances in miniaturizing science instruments for space missions, certain questions can only be answered by tools that are too large, heavy, and power-hungry to fly on spacecraft. Fortunately, there’s a way around this limitation: rather than bringing our tools to Mars, we can bring Mars samples back to Earth.

Your Guide to Mars

Mars, the Red Planet, once had liquid water on the surface and could have supported life. We don't know how it changed to the cold, dry desert-world it is today.

What are the specific benefits of bringing space samples back to Earth?

Precision. Some space-bound experiments can’t be done very precisely. One example is determining the origin and age of a rock, which is extremely important as we try to piece together just how long Mars may have been warm and wet for life to arise.

Reproducibility. Science is all about being able to reproduce your results, especially when those results could be something as astonishing as life on Mars. Even if a spacecraft found what looked like a microscopic fossilized cell, or a chemical signature that was identical to life on Earth, we need to reproduce those results using more than one science instrument in more than one laboratory.

Duration. When NASA returned samples from the Moon during the Apollo program, it knew technology would improve over time, so it stored some samples aside and even kept some sealed. Bringing Mars samples back from Earth would mean being able to pull them out for future generations.

How Mars Sample Return will work

Mars Sample Return Launch
Mars Sample Return Launch This artist's concept shows a rocket blasting tubes of rock and soil samples off the Martian surface towards orbit, where they would be collected by another spacecraft for return to Earth. NASA/JPL-Caltech

To date, humans have only returned samples to Earth from 3 other bodies in the solar system: the Moon, asteroid Itokawa, and the tailings of comet Wild 2. NASA’s Genesis mission collected and returned samples of solar wind, and samples from asteroids Ryugu and Bennu are scheduled to arrive back on Earth in 2020 and 2023, respectively.

Mars is a far more challenging destination than any of the above examples. It is farther away, with a thin atmosphere that complicates landings and a gravity field almost 40% as strong as Earth’s, which makes it harder to blast back off the surface. Only in the past decade have Mars landing technologies improved enough for us to be confident that we can land in the same spot multiple times—an ability needed for multi-spacecraft sample return missions.

Your Guide to NASA's Perseverance Rover

NASA's Perseverance rover will seek signs of life in Jezero crater, and store samples for future return to Earth.

NASA’s Perseverance rover, which launches to Mars in July 2020 and arrives in February 2021, is the first step of sample return. It will explore Jezero crater, the site of an ancient lake and river delta. There, the rover will use its onboard drill to collect samples from rocks that formed in Mars’ warm, wet past. It will seal the samples in small tubes and leave them on the surface for a future mission to return to Earth.

Getting those samples back to Earth will take 2 additional missions, for which NASA and the European Space Agency (ESA) will team up to share expertise and costs. As early as 2026, NASA and ESA will launch 2 new missions to Mars. The first will include a lander, a so-called “fetch rover,” and a launch system that will land together near Perseverance. The fetch rover will collect the samples dropped by Perseverance, bring them to the lander, and place them in a sample capsule inside a rocket. The rocket will launch the samples into Mars orbit.

Mars Sample Return Infographic
Mars Sample Return Infographic This infographic shows NASA and the European Space Agency's general plans for returning samples from Mars. The Planetary Society
Mars Sample Return components (ESA concept)
Mars Sample Return components (ESA concept) This artist's impression shows multiple components of the proposed NASA-ESA Mars Sample Return program: NASA's Mars Ascent Vehicle (left), ESA's Earth Return Orbiter (center), the Mars sample canister (top), and the Earth entry capsule (right). ESA/ATG Medialab

What happens if the fetch rover breaks down?

It’s always good to have a backup plan. Just in case something happens to the fetch rover, Perseverance also has the ability to carry the samples back to the lander and place them in the rocket.

The second mission will be a Mars orbiter that will support telecommunications for Perseverance, the lander, and the fetch rover. Once the sample capsule is launched, the orbiter will locate and dock with it, place it into a small capsule with a heat shield capable of surviving a trip through Earth’s atmosphere, and return home. If all goes well, the spacecraft will release the precious Mars samples to land in the Utah desert in 2031.

NASA and ESA have yet to decide where the Mars samples will be stored and studied, but it will be under the strictest possible quarantine protocols. We don’t want any Earth microbes contaminating the samples, or any Mars microbes contaminating us—however unlikely that may be. If life still exists on Mars, it’s probably under the surface, since Mars has no internally generated magnetic field or thick atmosphere to shield the planet from harmful solar radiation.

Planetary protection: keeping both worlds safe from contamination

NASA and many other space agencies have planetary protection offices that provide guidance and oversight that keeps space probes from contaminating other worlds, and vice versa.

What you can do to support Mars Sample Return

Getting Perseverance’s samples back to Earth will require the most ambitious Mars missions in history and require sustained public support to succeed. NASA and the European Space Agency have crafted an outline for those missions, but they are still in their early planning stages and not yet a certainty. We recently laid out specific steps Congress can take to make the missions happen. You can sign up for our Space Advocate newsletter and we’ll let you know when there are specific actions you can take. Want to learn the inner works of NASA, how Congress develops space legislation, and how to engage with your elected officials? Take our free Space Advocacy 101 course.

In the meantime, you can follow the excitement of NASA’s Perseverance rover mission by signing up for The Downlink, our weekly toolkit that contains news, announcements, and actions you can take to support space science and exploration. We couldn’t do any of this work without support from our members—consider joining today!

Finally, the world’s space agencies have sent dozens of missions to Mars over the years, resulting in a wealth of beautiful images that can be found in our space image library. Share those images and this page widely to help others get excited about Mars Sample Return and build public support for future Mars missions.