A Mars Sample-Return (MSR) mission is a proposed spaceflight mission to collect rock and dust samples on Mars and then return them to Earth. Sample-return would be a very powerful type of exploration, because the analysis is freed from the time, budget, and space constraints of spacecraft sensors.
According to Louis Friedman, Executive Director of The Planetary Society, a Mars sample-return mission is often described by the planetary science community as one of the most important robotic space missions, due to its high expected scientific return on investment and its ability to prove the technology needed for a human mission to Mars.
Over time, several concept missions have been studied, but none of them got beyond the study phase. The three latest concepts for an MSR mission are a NASA-ESA proposal, a Russian proposal (Mars-Grunt), and a Chinese proposal.
The return of Mars samples would benefit science by allowing more extensive analysis to be undertaken of the samples than could be done by instruments painstakingly transferred to Mars. Also, the presence of the samples on Earth would allow scientific equipment to be used on stored samples, even years and decades after the sample-return mission.
In 2006, MEPAG identified 55 important future science investigations related to the exploration of Mars. In 2008, they concluded that about half of the investigations "could be addressed to one degree or another by MSR", making MSR "the single mission that would make the most progress towards the entire list" of investigations. Moreover, it was found that a significant fraction of the investigations cannot be meaningfully advanced without returned samples.
One source of Mars samples is what are thought to be Martian meteorites, which are rocks ejected from Mars that made their way to Earth. As of April 2019, 266 meteorites have been identified as Martian, out of over 61,000 known meteorites. These meteorites are thought to be from Mars because they have elemental and isotopic compositions that are similar to rocks and atmosphere gases analyzed by spacecraft on Mars.
In 1996, the possibility of life on Mars was questioned again when apparent microfossils might have been found in a Mars meteorite (see ALH84001). This led to a renewed interest in a Mars sample-return, and several different architectures were considered. NASA administrator Goldin laid out three options for MSR: "paced", "accelerated", and "aggressive". It was thought that MSR could be done for less than US$100 million per year, with something similar to then-current Mars exploration budgets.
For at least three decades, Western scientists have advocated the return of geological samples from Mars. One concept was studied with the Sample Collection for Investigation of Mars (SCIM) proposal, which involved sending a spacecraft in a grazing pass through Mars upper atmosphere to collect dust and air samples without landing or orbiting.
The Soviet Union considered a Mars sample-return mission, Mars 5NM, in 1975 but it was cancelled due to the repeated failures of the N1 rocket that would have been used to launch it. A double sample-return mission, Mars 5M (Mars-79) planned for 1979, was cancelled due to complexity and technical problems.
One mission concept (provisionally named simply Mars Sample-Return) was originally considered by NASA's Mars Exploration Program to return samples by 2008, but was cancelled following a review of the program. In the summer of 2001, the Jet Propulsion Laboratory (JPL) requested mission concepts and proposals from industry-led teams (specifically Boeing, Lockheed Martin, and TRW). That following winter, JPL made similar requests of certain university aerospace engineering departments (namely both Massachusetts Institute of Technology (MIT) and the University of Michigan). A decade later, a NASA-ESA concept mission was aborted in 2012.
The United States' Mars Exploration Program, formed after Mars Observer's failure in September 1993, supported a Mars sample-return. One example of a mission architecture was the Groundbreaking Mars Sample-Return by Glenn J. MacPherson in the early 2000s.
In early 2011, the National Research Council (NRC)'s Planetary Science Decadal Survey, which laid out mission planning priorities for the period 2013–2022 at the request of NASA and the National Science Foundation (NSF), declared a MSR campaign its highest priority Flagship Mission for that period. In particular, it endorsed the proposed Mars Astrobiology Explorer-Cacher (MAX-C) mission in a "descoped" (less ambitious) form, although this mission plan was officially cancelled in April 2011.
The key mission requirement for the Perseverance rover was that it must help prepare NASA for its MSR campaign, which is needed before any crewed mission takes place. Such effort would require three additional vehicles: an orbiter, a fetch rover, and a two-stage, solid-fueled Mars ascent vehicle (MAV). In April 2020, an updated version of the mission was presented.
In mid-2006, the International Mars Architecture for the Return of Samples (iMARS) Working Group was chartered by the International Mars Exploration Working Group (IMEWG) to outline the scientific and engineering requirements of an internationally sponsored and executed Mars sample-return mission in the 2018–2023 time frame.
In October 2009, NASA and ESA established the Mars Exploration Joint Initiative to proceed with the ExoMars program, whose ultimate aim is "the return of samples from Mars in the 2020s". ExoMars' first mission would launch in 2018  with unspecified missions to return samples in the 2020–2022 time frame. The cancellation of the caching rover MAX-C, and later NASA withdrawal from ExoMars, pushed back a sample-return mission to an undetermined date. Due to budget limitations the MAX-C mission was cancelled in 2011, and the overall cooperation in 2012. The pull-out was described as "traumatic" for the science community.
In April 2018, a letter of intent was signed by NASA and ESA that may provide a basis for a Mars sample-return mission. In July 2019, a mission architecture was proposed to return samples to Earth by 2031: In April 2020, an updated version of the mission was presented.
In September 2012, NASA announced its intention to further study several strategies of bringing a sample of Mars to Earth – including a multiple launch scenario, a single-launch scenario, and a multiple-rover scenario – for a mission beginning as early as 2018. Dozens of samples would be collected and cached by the Mars 2020 rover, and would be left on the surface of Mars for possible later retrieval. A "fetch rover" would retrieve the sample caches and deliver them to a Mars ascent vehicle (MAV). In July 2018, NASA contracted Airbus to produce a "fetch rover" concept.
The MAV would launch from Mars and enter a 500 km orbit and rendezvous with a new Mars orbiter. The sample container would be transferred to an Earth entry vehicle (EEV) which would bring it to Earth, enter the atmosphere under a parachute and hard-land for retrieval and analyses in specially designed safe laboratories.
In this scenario, the sample-return mission would span two launches at an interval of about four years. The first launch would be for the orbiter, the second for the lander. The lander would include the two-stage, solid-fueled Mars Ascent Vehicle (MAV).
This concept would have the sample-return mission split into a total of three launches. In this scenario, the sample-collection rover (e.g. Mars 2020 rover) was launched separately to land on Mars first, and carry out analyses and sample collection over a lifetime of at least 500 Sols (Martian days).
Some years later, a Mars orbiter would be launched, followed by a lander carrying the two-stage, solid-fueled Mars Ascent Vehicle (MAV). The lander would bring a small and simple "fetch rover", whose sole function would be to retrieve the sample containers from the caches left on the surface or directly from the Perseverance rover, and return them to the lander where it would be loaded onto the MAV for delivery to the orbiter and then be sent to Earth.
This design would ease the schedule of the whole project, giving controllers time and flexibility to carry out the required operations. Furthermore, the program could rely on the successful landing system developed for the Mars Science Laboratory, avoiding the costs and risks associated with developing and testing yet another landing system from scratch.
SCIM (Sample Collection for Investigation of Mars) was a low-cost low-risk Mars sample-return mission design, proposed in the Mars Scout Program. SCIM would return dust and air samples without landing or orbiting, by dipping through the atmosphere as it collects Mars material. It uses heritage from the successful Stardust and Genesis sample-return missions.
Supports the development of the Mars Sample Return (MSR) mission that is planning to enter formulation (Phase A) as early as the summer of FY 2020. In FY 2021, MSR formulation activities include concept and technology development, and early design and studies in support of the Sample Return Lander and the Capture/Containment and Return System. It also supports a study of the facility required for the handling of returned samples. In developing concepts for a Mars Sample Return mission, the future budget supports an estimated MSR launch readiness date of 2026. Also included is funding for potential collaboration with Canada on the Mars Exploration Ice Mapper. The Mars Exploration Ice Mapper is a remote sensing mission under study intended to map and profile the near-surface (3–15 meters) water ice, particularly that which lies in the mid-latitude regions, in support of future science and exploration missions.
China is considering a Mars sample-return mission by 2030. The plan as of 2017 is to launch a large spacecraft that can carry out all phases of the mission, including sample collection, ascent from Mars, rendezvous in Mars orbit, and a flight back to Earth. Such a mission would require the super-heavy-lift Long March 9 launch vehicle. The needed technologies are to be tested during the Tianwen-1 mission launched in 2020. An alternative plan announced in 2019 involves using the 2020 HX-1 mission to cache the samples for retrieval in 2030. These samples would be retrieved by a sample collection lander with Mars ascent vehicle launched in November 2028 on a Long March 3B, and collected in Mars orbit using an Earth Return Orbiter launched on a Long March 5 also in November 2028, with return to Earth in September 2031.
France has worked towards a sample-return for many years. This included concepts of an extraterrestrial sample curation facility for returned samples, and numerous proposals. They worked on the development of a Mars sample-return orbiter, which would capture and return the samples as part of a joint mission with either the United States or other European countries.
On 9 June 2015, the Japanese Aerospace Exploration Agency (JAXA) unveiled a plan named Martian Moons Exploration (MMX) to retrieve samples from one of the moons of Mars. This mission will build on the expertise to be gained from the Hayabusa2 and SLIM missions. Of the two moons, Phobos's orbit is closer to Mars and its surface may have adhered particles blasted from the red planet; thus the Phobos samples collected by MMX may contain material originating from Mars itself. Japan has also shown interest in participating in an international Mars sample-return mission.
A Russian Mars sample-return mission concept is Mars-Grunt. It is meant to use Fobos-Grunt design heritage. Plans as of 2011 envisioned a two-stage architecture with an orbiter and a lander (but no roving capability), with samples gathered from the immediate surroundings of the lander by a robotic arm.
Since it is currently unknown whether life forms exist on Mars, the mission could potentially transfer viable organisms resulting in back contamination — the introduction of extraterrestrial organisms into Earth's biosphere. The scientific consensus is that the potential for large-scale effects, either through pathogenesis or ecological disruption, is extremely small. Returned samples from Mars will be treated as potentially biohazardous until scientists can determine that the returned samples are safe. The goal is to reduce the probability of release of a Mars particle to less than one in a million.
The proposed NASA Mars sample-return mission will not be approved by NASA until the National Environmental Policy Act (NEPA) process has been completed. Furthermore, under the terms of Article VII of the Outer Space Treaty and probably various other legal frameworks, were a release of organisms to occur, the releasing nation or nations would be liable for any resultant damages.
Part of the sample-return mission would be to prevent contact between the Martian environment and the exterior of the sample container. In order to eliminate the risk of parachute failure, the current plan is to use the thermal protection system to cushion the capsule upon impact (at terminal velocity). The sample container will be designed to withstand the force of the impact. To receive the returned samples, NASA proposed a specially designed Biosafety Level 4 containment facility, the Mars Sample-Return Receiving facility (MSRRF). Not knowing what properties (e.g., size) any Martian organisms might exhibit is a complication in design of such a facility.
Other scientists and engineers, notably Robert Zubrin of the Mars Society, argued in the fringe Journal of Cosmology that contamination risk is functionally zero and there is little need to worry. They cite, among other things, lack of any verifiable incident although trillions of kilograms of material have been exchanged between Mars and Earth due to meteorite impacts.
The International Committee Against Mars Sample Return (ICAMSR) is a small advocacy group led by Barry DiGregorio, who campaigns against a Mars sample-return mission. While ICAMSR acknowledges a low probability for biohazards, it considers the proposed containment measures insufficient, and unsafe at this stage. ICAMSR is demanding more in situ studies on Mars first, and preliminary biohazard testing at the International Space Station before the samples are brought to Earth. DiGregorio supports the conspiracy theory of a NASA coverup regarding the discovery of microbial life by the 1976 Viking landers. DiGregorio also supports a fringe view that several pathogens - such as common viruses - originate in space and probably caused some of the mass extinctions, and deadly pandemics. These claims connecting terrestrial disease and extraterrestrial pathogens have been rejected by the scientific community.
The Sample-Return Robot Challenge, as part of NASA's Centennial Challenges program, offered a total US$1.5 million to teams that can build fully autonomous robots that can find, retrieve, and return up to 10 different sample types within a large outdoor environment (80,000 m2). The challenge started in 2012 and ended in 2016. Over 50 teams competed during the 5-year duration of the competition. A robot named Cataglyphis, developed by Team Mountaineers from West Virginia University completed the final challenge in 2016.