A sample-return mission is a
spacecraft
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, ...
mission to collect and return samples from an extraterrestrial location to Earth for analysis. Sample-return missions may bring back merely atoms and molecules or a deposit of complex compounds such as loose material and rocks. These samples may be obtained in a number of ways, such as soil and rock excavation or a collector array used for capturing particles of solar wind or cometary debris. Nonetheless, concerns have been raised that the return of such samples to planet Earth may endanger Earth itself.
To date, samples of
Moon rock
Moon rock or lunar rock is rock originating from Earth's Moon. This includes lunar material collected during the course of human exploration of the Moon, and rock that has been ejected naturally from the Moon's surface and landed on Earth a ...
from Earth's
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
have been collected by robotic and crewed missions, the comet
Wild 2
Comet 81P/Wild, also known as Wild 2 (pronounced "vilt two") ( ), is a comet named after Swiss astronomer Paul Wild, who discovered it on January 6, 1978, using a 40-cm Schmidt telescope at Zimmerwald, Switzerland.
For most of its 4.5 billion- ...
and the asteroids
25143 Itokawa and
162173 Ryugu have been visited by robotic spacecraft which returned samples to Earth, and samples of the
solar wind have been returned by the robotic ''
Genesis
Genesis may refer to:
Bible
* Book of Genesis, the first book of the biblical scriptures of both Judaism and Christianity, describing the creation of the Earth and of mankind
* Genesis creation narrative, the first several chapters of the Book of ...
'' mission. Samples from the asteroid
101955 Bennu are en route back to Earth and are expected to arrive in September 2023.
In addition to sample-return missions, samples from three identified non-terrestrial bodies have been collected by other means: samples from the Moon in the form of
Lunar meteorite
A lunar meteorite is a meteorite that is known to have originated on the Moon. A meteorite hitting the Moon is normally classified as a transient lunar phenomenon.
Discovery
In January 1982, John Schutt, leading an expedition in Antarctica for ...
s, samples from
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
in the form of
Martian meteorites, and samples from
Vesta in the form of
HED meteorite
HED meteorites are a clan (subgroup) of achondrite meteorites. HED stands for "howardite– eucrite– diogenite".
These achondrites came from a differentiated parent body and experienced extensive igneous processing not much different from the ma ...
s.
Scientific use
Samples available on Earth can be analyzed in
laboratories
A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physi ...
, so we can further our understanding and knowledge as part of the
discovery and exploration of the Solar System. Until now, many important scientific discoveries about the
Solar System
The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
were made remotely with
telescope
A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to obse ...
s, and some Solar System bodies were visited by orbiting or even landing spacecraft with instruments capable of
remote sensing
Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Ear ...
or sample analysis. While such an investigation of the Solar System is technically easier than a sample-return mission, the scientific tools available on Earth to study such samples are far more advanced and diverse than those that can go on spacecraft. Further, analysis of samples on Earth allows follow up of any findings with different tools, including tools that can tell intrinsic extraterrestrial material from terrestrial contamination, and those that have yet to be developed; in contrast, a spacecraft can carry only a limited set of analytic tools, and these have to be chosen and built long before launch.
Samples analyzed on Earth can be matched against findings of remote sensing for more insight into the
processes that formed the Solar System. This was done, for example, with findings by the
''Dawn'' spacecraft, which visited the asteroid Vesta from 2011 to 2012 for imaging, and samples from
HED meteorite
HED meteorites are a clan (subgroup) of achondrite meteorites. HED stands for "howardite– eucrite– diogenite".
These achondrites came from a differentiated parent body and experienced extensive igneous processing not much different from the ma ...
s (collected on Earth until then), which were compared to data gathered by Dawn. These meteorites could then be identified as material ejected from the large impact crater
Rheasilvia on Vesta. This allowed deducing the composition of the crust,
mantle
A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that.
Mantle may refer to:
*Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear
**Mantle (vesture), an Eastern Orthodox ve ...
and core of Vesta. Similarly, some
differences in the composition of asteroids (and, to a lesser extent, different compositions of
comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...
s) can be discerned by imaging alone. However, for a more precise inventory of the material on these different bodies, more samples will be collected and returned in the future, to match their compositions with the data gathered through telescopes and
astronomical spectroscopy
Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars an ...
.
One further focus of such investigation—besides the basic composition and
geologic history of the various Solar System bodies—is the presence of the
building blocks of life on comets, asteroids,
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
or the moons of the
gas giants. Several sample-return missions to asteroids and comets are currently in the works. More samples from asteroids and comets will help determine whether life formed in space and was carried to Earth by meteorites. Another question under investigation is whether
extraterrestrial life
Extraterrestrial life, colloquially referred to as alien life, is life that may occur outside Earth and which did not originate on Earth. No extraterrestrial life has yet been conclusively detected, although efforts are underway. Such life might ...
formed on other Solar System bodies like Mars or on
the moons of the gas giants, and whether life might even exist there. The result of NASA's last "Decadal Survey" was to prioritize a Mars sample-return mission, as Mars has a special importance: it is comparatively "nearby", might have harbored life in the past, and might even continue to sustain life.
Jupiter's moon
Europa
Europa may refer to:
Places
* Europe
* Europa (Roman province), a province within the Diocese of Thrace
* Europa (Seville Metro), Seville, Spain; a station on the Seville Metro
* Europa City, Paris, France; a planned development
* Europa Clif ...
is another important focus in the search for life in the Solar System. However, due to the distance and other constraints, Europa might not be the target of a sample-return mission in the foreseeable future.
Planetary protection
Planetary protection aims to prevent biological contamination of both the target
celestial body
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...
and the
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
in the case of sample-return missions. A sample return from Mars or other location with the potential to host life is a
category V mission under COSPAR, which directs to the containment of any unsterilized sample returned to Earth. This is because it is unknown what the effects such hypothetical life would be on humans or the
biosphere of Earth.
[Joshua Lederberg]
Parasites Face a Perpetual Dilemma
(PDF). Volume 65, Number 2, 1999 / ''American Society for Microbiology News'' 77. For this reason,
Carl Sagan
Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. His best known scientific contribution is research on ex ...
and
Joshua Lederberg argued in the 1970s that we should do sample-return missions classified as category V missions with extreme caution, and later studies by the NRC and ESF agreed.
[Preliminary Planning for an International Mars Sample Return Mission Report]
of the International Mars Architecture for the Return of Samples (iMARS) Working Group June 1, 2008.[European Science Foundation – Mars Sample Return backward contamination – Strategic advice and requirements]
July, 2012, – see Back Planetary Protection section. (for more details of the document se
abstract
.[Mars Sample Return: Issues and Recommendations]
Task Group on Issues in Sample Return. National Academies Press, Washington, DC (1997).
Sample-return missions
First missions
The
Apollo program returned over of
lunar rocks and
regolith (including
lunar 'soil') to the
Lunar Receiving Laboratory in
Houston
Houston (; ) is the most populous city in Texas, the most populous city in the Southern United States, the fourth-most populous city in the United States, and the sixth-most populous city in North America, with a population of 2,304,580 ...
.
[ Orloff 2004]
"Extravehicular Activity"
/ref> Today, 75% of the samples are stored at the Lunar Sample Laboratory Facility
The Lunar Sample Laboratory Facility (LSLF) is a repository and laboratory facility at NASA's Lyndon B. Johnson Space Center in Houston, Texas, opened in 1979 to house geologic samples returned from the Moon by the Apollo program missions to t ...
built in 1979. In July 1969, Apollo 11
Apollo 11 (July 16–24, 1969) was the American spaceflight that first landed humans on the Moon. Commander Neil Armstrong and lunar module pilot Buzz Aldrin landed the Apollo Lunar Module ''Eagle'' on July 20, 1969, at 20:17 UTC, ...
achieved the first successful sample return from another Solar System body. It returned approximately of Lunar surface material. This was followed by of material and Surveyor 3 parts from Apollo 12
Apollo 12 (November 14–24, 1969) was the sixth crewed flight in the United States Apollo program and the second to land on the Moon. It was launched on November 14, 1969, by NASA from the Kennedy Space Center, Florida. Commander Charles ...
, of material from Apollo 14
Apollo 14 (January 31, 1971February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to land on the Moon, and the first to land in the lunar highlands. It was the last of the " H missions", landings at ...
, of material from Apollo 15
Apollo 15 (July 26August 7, 1971) was the ninth crewed mission in the United States' Apollo program and the fourth to land on the Moon. It was the first J mission, with a longer stay on the Moon and a greater focus on science than ear ...
, of material from Apollo 16
Apollo 16 (April 1627, 1972) was the tenth human spaceflight, crewed mission in the United States Apollo program, Apollo space program, administered by NASA, and the fifth and penultimate to Moon landing, land on the Moon. It was the second o ...
, and of material from Apollo 17
Apollo 17 (December 7–19, 1972) was the final mission of NASA's Apollo program, the most recent time humans have set foot on the Moon or traveled beyond low Earth orbit. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walke ...
.
One of the most significant advances in sample-return missions occurred in 1970 when the robotic Soviet
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
mission known as Luna 16 successfully returned of lunar soil. Likewise, Luna 20 returned in 1974, and Luna 24 returned in 1976. Although they recovered far less than the Apollo missions, they did this fully automatically. Apart from these three successes, other attempts under the Luna programme failed. The first two missions were intended to outstrip Apollo 11 and were undertaken shortly before them in June and July 1969: Luna E-8-5 No. 402 failed at start, and Luna 15 crashed on the Moon. Later, other sample-return missions failed: Kosmos 300 and Kosmos 305 in 1969, Luna E-8-5 No. 405 in 1970, Luna E-8-5M No. 412 in 1975 had unsuccessful launches, and Luna 18 in 1971 and Luna 23 in 1974 had unsuccessful landings on the Moon.
In 1970, the Soviet Union planned for a 1975 first Martian sample-return mission in the Mars 5NM
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atmosph ...
project. This mission was planned to use an N1 rocket, but as this rocket never flew successfully, the mission evolved into the Mars 5M Mars 5M, also known as Mars 79 (russian: Марс-5М, or ) was a cancelled Mars sample return mission that the Soviet Union was planning in the 1970s.
History
Mars 5M grew out of the Mars 5NM and Mars 4NM missions that were canceled along with ...
project, which would use a double launch with the smaller Proton
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...
rocket and an assembly at a Salyut space station. This Mars 5M mission was planned for 1979, but was canceled in 1977 due to technical problems and complexity; all hardware was ordered destroyed.
1990s
The Orbital Debris Collection (ODC) experiment deployed on the Mir space station for 18 months in 1996–97 used aerogel
Aerogels are a class of synthetic porous ultralight material derived from a gel, in which the liquid component for the gel has been replaced with a gas, without significant collapse of the gel structure. The result is a solid with extremely low ...
to capture particles from low Earth orbit, including both interplanetary dust and man-made particles.
2000s
The next mission to return extraterrestrial samples was the ''Genesis
Genesis may refer to:
Bible
* Book of Genesis, the first book of the biblical scriptures of both Judaism and Christianity, describing the creation of the Earth and of mankind
* Genesis creation narrative, the first several chapters of the Book of ...
'' mission, which returned solar wind samples to Earth from beyond Earth orbit in 2004. Unfortunately, the ''Genesis'' capsule failed to open its parachute while re-entering the Earth's atmosphere and crash-landed in the Utah desert. There were fears of severe contamination or even total mission loss, but scientists managed to save many of the samples. They were the first to be collected from beyond lunar orbit. ''Genesis'' used a collector array made of wafers of ultra-pure silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
, gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
, sapphire
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived via the Latin "sa ...
, and diamond
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, b ...
. Each different wafer was used to collect a different part of the solar wind.
''Genesis'' was followed by NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeedin ...
's ''Stardust
Stardust may refer to:
* A type of cosmic dust, composed of particles in space
Entertainment Songs
* “Stardust” (1927 song), by Hoagy Carmichael
* “Stardust” (David Essex song), 1974
* “Stardust” (Lena Meyer-Landrut song), 2012
* ...
'' spacecraft, which returned comet samples to Earth on January 15, 2006. It safely passed by Comet Wild 2 and collected dust samples from the comet's coma
A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...
while imaging the comet's nucleus. ''Stardust'' used a collector array made of low-density aerogel (99% of which is space), which has about 1/1000 of the density of glass. This enables the collection of cometary particles without damaging them due to high impact velocities. Particle collisions with even slightly porous solid collectors would result in the destruction of those particles and damage to the collection apparatus. During the cruise, the array collected at least seven interstellar dust particles.
2010s and 2020s
In June 2010 the Japan Aerospace Exploration Agency
The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...
(JAXA) Hayabusa probe returned asteroid samples to Earth after a rendezvous with (and a landing on) S-type asteroid
S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the secon ...
25143 Itokawa. In November 2010, scientists at the agency confirmed that, despite failure of the sampling device, the probe retrieved micrograms of dust from the asteroid, the first brought back to Earth in pristine condition.
The Russian Fobos-Grunt was a failed sample-return mission designed to return samples from Phobos, one of the moons of Mars. It was launched on November 8, 2011, but failed to leave Earth orbit and crashed after several weeks into the southern Pacific Ocean.
The Japan Aerospace Exploration Agency
The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...
(JAXA) launched the improved ''Hayabusa2
is an asteroid sample-return mission operated by the Japanese state space agency JAXA. It is a successor to the '' Hayabusa'' mission, which returned asteroid samples for the first time in June 2010. ''Hayabusa2'' was launched on 3 December ...
'' space probe on December 3, 2014. ''Hayabusa2'' arrived at the target near-Earth C-type asteroid 162173 Ryugu (previously designated ) on 27 June 2018. It surveyed the asteroid for a year and a half and took samples. It left the asteroid in November 2019 and returned to Earth on December 6, 2020.
The OSIRIS-REx mission was launched in September 2016 on a mission to return samples from the asteroid 101955 Bennu. The samples are expected to enable scientists to learn more about the time before the birth of the Solar System, initial stages of planet formation, and the source of organic compounds that led to the formation of life. It reached the proximity of Bennu on 3 December 2018, where it began analyzing its surface for a target sample area over the next several months. It collected its sample on 20 October 2020, and is expected to return to Earth on 24 September 2023.
China launched the Chang'e 5 lunar sample return mission on November 23, 2020, which returned to Earth with 2 kilograms of lunar soil on December 16, 2020. It was first lunar sample return in over 40 years.
Future missions
Russia has plans for Luna-Glob missions to return samples from the Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
by 2027 and Mars-Grunt to return samples from Mars in the late 2020s.
JAXA is developing the MMX MMX may refer to:
* 2010, in Roman numerals
Science and technology
* MMX (instruction set), a single-instruction, multiple-data instruction set designed by Intel
* MMX Mineração, a Brazilian mining company
* Martian Moons eXploration, a Japane ...
mission, a sample-return mission to Phobos that will be launched in 2024. MMX will study both moons of Mars, but the landing and the sample collection will be on Phobos. This selection was made because of the two moons, Phobos's orbit is closer to Mars and its surface may have particles blasted from Mars. Thus the sample may contain material originating on Mars itself. A propulsion module carrying the sample is expected to return to Earth in approximately September 2029.
China will launch the Chang'e 6 lunar sample return mission in 2023. China is also planning a mission called Tianwen-2
''Tianwen-2'', formerly known as ''ZhengHe'', is a planned Chinese asteroid sample-return and comet exploration mission that is currently under development.
Overview
''Tianwen-2'' is planned to be launched by a Long March 3B rocket around 20 ...
to return samples from 469219 Kamoʻoalewa which is planned to launch in 2024. China plans for a Mars sample return mission by 2030. Also, the Chinese Space Agency is designing a sample-retrieval mission from Ceres that would take place during the 2020s.
NASA and ESA has long planned a Mars Sample-Return Mission, which is only now coming to fruition. The ''Perseverance'' rover, deployed in 2020, is collecting drill core samples and stashing them on the Mars surface. A joint NASA- ESA mission to return them is planned for the late twenties, consisting of a lander to retrieve the samples and raise them into orbit, and an orbiter to return them to Earth.
Comet sample-return missions also continue to be a NASA priority. Comet Surface Sample Return was one of the six themes for proposals for NASA's fourth New Frontiers mission in 2017.
Methods of sample return
Sample-return methods include, but are not restricted to the following:
Collector array
A collector array may be used to collect millions or billions of atoms, molecules, and fine particulates by using wafers made of different elements. The molecular structure of these wafers allows the collection of various sizes of particles. Collector arrays, such as those flown on ''Genesis'', are ultra-pure in order to ensure maximal collection efficiency, durability, and analytical distinguishability.
Collector arrays are useful for collecting tiny, fast-moving atoms such as those expelled by the Sun through the solar wind, but can also be used for collection of larger particles such as those found in the coma of a comet. The NASA spacecraft known as ''Stardust'' implemented this technique. However, due to the high speeds and size of the particles that make up the coma and the area nearby, a dense solid-state collector array was not viable. As a result, another means for collecting samples had to be designed to preserve the safety of the spacecraft and the samples themselves.
Aerogel
Aerogel is a silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
-based porous solid with a sponge-like structure, 99.8% of whose volume is empty space. Aerogel has about 1/1000 of the density of glass. An aerogel was used in the ''Stardust'' spacecraft because the dust particles the spacecraft was to collect would have an impact speed of about 6 km/s. A collision with a dense solid at that speed could alter their chemical composition
A chemical composition specifies the identity, arrangement, and ratio of the elements making up a compound.
Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for ...
or perhaps vaporize them completely.
Since the aerogel is mostly transparent, and the particles leave a carrot-shaped path once they penetrate the surface, scientists can easily find and retrieve them. Since its pores are on the nanometer
330px, Different lengths as in respect to the molecular scale.
The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re, ...
scale, particles, even ones smaller than a grain of sand, do not merely pass through the aerogel completely. Instead, they slow to a stop and then are embedded within it. The ''Stardust'' spacecraft has a tennis-racket-shaped collector with aerogel fitted to it. The collector is retracted into its capsule for safe storage and delivery back to Earth. Aerogel is quite strong and easily survives both launching and outer-space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predo ...
environments.
Robotic excavation and return
Some of the riskiest and most difficult types of sample-return missions are those that require landing on an extraterrestrial body such as an asteroid, moon, or planet. It takes a great deal of time, money, and technical ability to even initiate such plans. It is a difficult feat that requires that everything from launch to landing to retrieval and launch back to Earth is planned out with high precision and accuracy.
This type of sample return, although having the most risks, is the most rewarding for planetary science. Furthermore, such missions carry a great deal of public outreach potential, which is an important attribute for space exploration
Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is carried out mainly by astronomers with telescopes, its physical exploration though is conducted both by uncrewed robo ...
when it comes to public support. The only successful robotic sample-return missions of this type have been the Soviet Luna landers and Chinese Chang'e 5.
List of missions
Colour key:
Crewed missions
Robotic missions
See also
* Asteroid mining
* Exploration of Mars
* Exploration of the Moon
* Extraterrestrial sample curation
The curation of extraterrestrial samples (astromaterials) obtained by sample-return missions take place at facilities specially designed to preserve both the sample integrity and protect the Earth. Astromaterials are classified as either ''non-re ...
* List of lunar probes
This is a list of robotic space probes that have flown by, impacted, orbited or landed on the Moon for the purpose of lunar exploration, as well as probes launched toward the Moon that failed to reach their target.
The crewed Apollo missions ...
* Robotic exploration of the Moon
* Timeline of Solar System exploration
Notes
References
External links
Mars Exploration: ''Sample Returns''
Jet Propulsion Laboratory Mars Exploration Program on sample return missions.
Stardust ''Homepage''
Jet Propulsion Laboratory ''Stardust'' mission website.
Genesis Mission ''Homepage''
Jet Propulsion Laboratory ''Genesis'' mission website.
''Stardust'' website on aerogel technology.
JAXA ''Hayabusa'' project update.
MarsNews.com: ''Mars Sample Return''
MarsNews.com on Mars Sample Return missions.
A list of missions to the Moon from 1958 to 1998.
Evaluating the Biological Potential in Samples Returned from Planetary Satellites and Small Solar System Bodies
The National Academies, Space Science Board 1998
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Discovery and exploration of the Solar System
Space hazards
Spaceflight
Spaceflight timelines