Mars sample-return mission
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A Mars sample-return (MSR) mission is a proposed spaceflight mission to collect rock and dust samples on Mars and return them to Earth. A sample return would be a very powerful type of exploration allowing the analysis to be freed from the time, budget, and space constraints of spacecraft sensors.
Many concept missions have been studied, but none of them have gone beyond the study phase. The three most recent concepts for an MSR mission are a NASA-ESA proposal, a Chinese proposal, and a Russian proposal, Mars-Grunt. Although NASA and ESA's plans to return the samples to Earth are still at a very early stage, as of 2021, samples are being gathered on Mars by the Perseverance rover.
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. Additionally, the presence of the samples on Earth would allow scientific equipment to be used on stored samples even decades after the sample-return mission.
In 2006, the Mars Exploration Program Analysis Group identified 55 important future scientific 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 believed 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 raised when apparent microfossils were thought to have been found in a Mars meteorite, ALH84001. This hypothesis was eventually rejected, but at the time the discovery, it led to a renewed interest in a Mars sample return, and several different architectures were considered.
For at least three decades, scientists have advocated the return of geological samples from Mars. One early concept was the Sample Collection for Investigation of Mars (SCIM) proposal, which involved sending a spacecraft in a grazing pass through Mars's 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. Another sample-return mission, Mars 5M (Mars-79), planned for 1979, was cancelled due to complexity and technical problems.
A mission concept was 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 (Boeing, Lockheed Martin, and TRW). That following winter, JPL made similar requests of certain university aerospace engineering departments (MIT and the University of Michigan). In 2012, a NASA-ESA concept mission was cancelled.
The United States' Mars Exploration Program, formed after Mars Observer's failure in September 1993, supported a Mars sample return. One architecture was proposed by Glenn J. MacPherson in the early 2000s.
In early 2011, the US National Research Council's Planetary Science Decadal Survey, which laid out mission planning priorities for the period 2013–2022, declared an 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. This mission plan was officially cancelled in April 2011. In September 2012, the Mars Program Planning Group endorsed a sample return after evaluating long-term Mars plans.
The key mission requirement for the Mars 2020 Perseverance rover mission was that it must help prepare NASA for its MSR campaign. This effort will require three additional vehicles: an orbiter, a fetch rover, and a two-stage, solid-fueled Mars Ascent Vehicle (MAV).
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's 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 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, which will have flexible wheels for fast retrieval of samples.
The MAV will launch from Mars and enter a 500 km orbit. It will remain stowed inside a cylinder on the lander and will have a thermal protective coating. The rocket will have the first stage run by a single updated STAR-20 burning for first 70 seconds of flight, and the second stage will have a single updated STAR-15 engine burning for another 27 seconds. Both will be separated by a coast phase, after which it will release the sample container in orbit. The sample will then rendezvous with a new Mars orbiter. The sample container will be caught by the orbiter using the NASA built Capture and Containment and Return System payload on it. It will then be transferred and stowed in an Earth entry vehicle (EEV), which will bring it to Earth, entering the atmosphere with a parachute, and hard-land for retrieval and analyses in specially designed safe laboratories.
Some years later, a Mars orbiter will be launched, followed by a lander carrying the two-stage, solid-fueled Mars Ascent Vehicle (MAV). The lander will bring a small and simple "fetch rover", whose sole function will 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 will be loaded onto the MAV for delivery to the orbiter and then be sent to Earth.
This design will ease the schedule of the whole project, giving controllers time and flexibility to carry out the required operations. Furthermore, the program can 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.
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:
- The Mars 2020 Perseverance rover launched on 30 July 2020 and landed on 18 February 2021 in Jezero Crater will collect samples and store them in 43 cylindrical tubes, leaving them behind on the surface for later retrieval.
- NASA's sample retrieval lander with a 3-meter long, two-stage, solid-fueled Mars ascent rocket (developed by NASA) and a sample collection fetch rover (developed by ESA) will launch in July 2026. It will land near the Mars 2020 rover Octavia E. Butler Landing site in August 2028. The new rover will collect the samples left behind by Mars 2020 with a robotic arm and will deliver them to the lander. If Mars 2020 is still operational, it could also deliver sample tubes to the landing site.
- The lander will then use its robotic arm to take the sample tubes from the rover and load them into the sample Return Capsule inside the rocket’s payload fairing by its own systems. Once loaded with the samples, the Mars ascent rocket will launch with the sample return canister in spring 2029 and reach a low Mars orbit.
- The ESA-built Earth-return orbiter will launch on an Ariane 6 rocket in October 2026 and will arrive at Mars in 2027, using ion propulsion and a separate propulsion element to gradually lower its orbit to the proper low Martian orbit by July 2028. The orbiter will retrieve and seal the canister with the samples in orbit and use a NASA built orbiter robotic arm to place the sealed container into an Earth-entry capsule. It will raise its orbit, release the propulsion element, and return it to Earth during the 2031 Mars-to-Earth transfer window.
- The sample return canister, encapsulated within the Earth re-entry capsule, will land on Earth in 2031.
Samples gathered by Perseverance rover
The 2020 Mars rover Perseverance landed in the crater Jezero in February 2021, which appears to be an ancient lakebed, making it suitable for ground sampling which hopefully will reveal whether or not Mars harbored life in ancient times.
- In the beginning of August 2021, the 2020 Mars rover Perseverance made the first attempt to collect a ground sample by drilling out a finger-size core of Martian rock to return to Earth. This attempt did not succeed. A drill hole was produced, as indicated by instrument readings, and proven by a clear photograph of the drill hole. However, the sample container turned out to be empty. This was interpreted as indicating that the rock sampled was not robust enough to produce an intact core.
- A new attempt with a target rock judged to have better chances to yield a sufficiently robust sample was made at the end of August and the beginning of September 2021. After abrasing the target rock, cleaning away the dust produced by means of puffs of high pressurized nitrogen, and inspecting the resulting rock surface, a hole was drilled on September 1. A rock sample appeared to be in the tube, but it was not immediately placed in a sample container. A new procedure of inspecting the tube optically was performed. This procedure was introduced in order to avoid setbacks as with the earlier attempt. On September 6, the process was completed and the first sample placed in a closed titanium container.
|Samples Taken||Date||Contents||Rock Name||Location||Notes|
|Tube 1||7 July 2021||Witness Tube||N/A||North Séítah Unit||This was taken as a dry-run in preparation for later sampling attempts, and did not aim to sample a rock.|
|Tube 2||5 August 2021||Atmospheric Gas||Roubion||Cratered Floor Fractured Rough Unit||Attempted to sample the rock but did not succeed|
|Tube 3||1 September 2021||Soil Sample||Rochette||Citadelle, South Séítah Unit||First successful sample.|
||8 September 2021||Soil Sample||Rochette||Citadelle, South Séítah Unit||Sampled from same rock as previous.|
||15 November 2021||Soil Sample|
China is considering a Mars sample-return mission by 2030. As of 2017, the plan was 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 have required the super-heavy-lift Long March 9 launch vehicle. The needed technologies were tested during the Tianwen-1 mission launched in 2020. There was also a plan that involved using the 2020 HX-1 mission to cache the samples for retrieval in 2030.
In 2019, an alternative plan was announced (and subsequently adopted in 2021) where the samples would be retrieved by a sample collection lander with a Mars ascent vehicle within an aeroshell attached to a propulsion module (not another orbiter like Tianwen-1 mission) launched in November 2028 on a Long March 3B, and collected in Mars orbit using an Earth Return Orbiter and re-entry capsule 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. The launch from the Earth is planned for September 2024, with a return to the Earth in 2029. 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.
Potential for back contamination
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.
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