Mars sample-return mission

A Mars sample-return (MSR) mission is a proposed mission to collect rock and dust samples on Mars and return them to Earth. Such a mission would allow more extensive analysis than that allowed by onboard sensors. Risks of cross-contamination of the Earth biosphere from returned Martian samples have been raised, though the risk of this occurring is considered to be low. Some of the most recent concepts are a NASA-ESA proposal; a CNSA proposal, Tianwen-3; and a Roscosmos proposal, Mars-Grunt. In addition, a JAXA proposal, Martian Moons eXploration (MMX,) is aimed at returning samples from Phobos. Although NASA and ESA's plans to return the samples to Earth are still in the design stage as of 2024, samples have been gathered on Mars by the Perseverance rover.

Scientific value

Once returned to Earth, stored samples can be studied with the most sophisticated science instruments available. Thomas Zurbuchen, associate administrator for science at NASA Headquarters in Washington, expects such studies to allow several new discoveries at many fields. Samples may be reanalyzed in the future by instruments that do not yet exist. In 2006, the Mars Exploration Program Analysis Group identified 55 important investigations related to Mars exploration. 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 reported that a significant fraction of the investigations could not 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 August 2023, 356 meteorites had been identified as Martian, out of over 79,000 known meteorites. These meteorites are believed to be from Mars because their elemental and isotopic compositions are similar to rocks and atmospheric gases analyzed on Mars.

History

Before 1990

Returning from Mars appeared in technical literature when Apollo was still in development and the first spacecraft to fly past Mars had not yet launched, with an expectation that people would be on board for Mars ascent. The density of the Mars atmosphere remained unknown at that time, so the Lockheed engineering author reported the analysis of trajectory options over a range of aerodynamic drag conditions for a 15-ton launch vehicle to reach a rendezvous orbit. At NASA, returning samples from Mars was studied jointly by the Langley Research Center and the Jet Propulsion Laboratory in the early 1970s during the time that the Viking Mars lander mission was in development, and a Langley author noted that the "Mars surface-to-orbit launch vehicle" would need high performance because its mass would "have a substantial impact on the mass and systems requirements" for earlier mission phases, delivery of that vehicle to Mars and launch preparations on Mars. 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 launched it. Another sample-return mission, Mars 5M (Mars-79), planned for 1979, was cancelled due to complexity and technical problems. In the mid-1980's, JPL mission planners noted that MSR had been "pushed by budgetary and other pressures into the '90s," and that the round trip would "impose large propulsion requirements." They presented a notional mass budget for a concept that would launch a 9.5-metric-ton payload from Earth, including a Mars orbiter for Earth return, and a lander having a 400-kg rover and a "Mars return vehicle" that would mass over 2 metric tons. A 20-kg sample canister would arrive at Earth containing 5 kg of samples including scientific-quality cores drilled from every type of Mars terrain. In the late 1980s, multiple NASA centers contributed to a proposed Mars Rover Sample Return mission (MRSR). As described by JPL authors, one option for MRSR relied on a single launch of a 12-ton package including a Mars orbiter and Earth return vehicle, a 700-kg rover, and a 2.7-ton Mars ascent vehicle (MAV) which would use pump-fed liquid propulsion for a significant mass saving. A 20-kg sample package on the MAV was to contain 5 kg of Mars soil. A Johnson Space Center author subsequently referred to a launch from Earth in 1998 with a MAV mass in the range 1400 to 1500 kg including a pump-fed first stage and a pressure-fed second stage.

1990 onward

… excerpt ends here. Continue reading the full article.